conference: 11 and 12 january 2017, exhibition: 10, 11 and ... · parthasarathy n, head, driveline...

Volume: 2 Issue: 2 June - July 2016 ` 10/-Bimonthly, Chennai

IWTMAINDIAN WIND TURBINE MANUFACTURERS ASSOCIATION

WINDERGY INDIA 2017Conference: 11th and 12th January 2017,

Exhibition: 10th, 11th and 12th January 2017at The Ashok, New Delhi

announce

&

A Bi-monthly Magazine of Indian Wind Turbine Manufacturers Association

Volume: 2 Issue: 2 June - July 2016

Executive Committee

Contents Page No.

Wind Turbine Gearbox 3

Parthasarathy N, Head, Driveline Engineering, Romax Solutions Pvt. Ltd.Stephen Brown, VP, Engineering, Romax Technologies, UK

Estimating Fatigue Life of Gears in HALT Test for Wind Turbine Gearboxes 12

M. Mahendran, Head – Engineering, Shanthi Gears Limited, C-Unit, Avinashi Road, Muthugoundenpudur Post, Coimbatore - 641 406, India

Securing Reliability for Gearboxes of Giant Multi-Megawatt Turbines 22

Dr. Andreas Klein, winergy - Head of EngineeringMatthias Deicke, winergy - Head of Electrical SystemsDr. Thomas Meyer, winergy - Manager New Bearing TechnologiesWinergy - Siemens AG, Am Industriepark -2, 46562, Voerde, Germany

Energy Management System - ISO 50001‘A Commitment of Optimum Energy to Customer’ 24

Dr. Sanjiv Kawishwar - Sr VP , ReGen Powertech, India

Competitive Gearboxes for Reliability 26

Sonja Goris, Innovation Manager, ZF Wind Power Antwerpen NV,A Business Unit of ZF Friedrichshafen AG, Belgium

The Computer Simulation on Wind Turbine Gearbox Design 28

Shigang Chen, Gearbox Research Institute, Dalian Huarui Heavy Industry Group Co., Ltd., Dalian, ChinaZheng Li, Dalian Martitime University, Dalian, China

Wind Mill Gearbox Failure Modes and Repairing – Service with Accuracy 34

Mr. P. Kanakaraj, Managing Director, M/s. Kay Arr Engineering ServicesKannampalayam, Sulur, Coimbatore

Snippets on Wind Power 38

Compiled By: Mr. Abhijit Kulkarni, Business Unit Head -Energy Segment, SKF India Ltd, Pune and IWTMA Team

Photo Feature 39

Know Your Member - Suzlon 40

Indian Wind Turbine Manufacturers Association4th Floor, Samson Tower, 403 L, Pantheon Road, Egmore

Chennai - 600 008. Tel : 044 43015773 Fax : 044 4301 6132Email : [email protected]

[email protected] : www.indianwindpower.com

(For Internal Circulation only)

Views expressed in the magazine are those of the authors and do not necessarily reflect those of the Association, Editor, Publisher or Author's Organization.

Chairman

Mr. Sarvesh KumarDeputy Managing DirectorRRB Energy Limited, New Delhi

Vice Chairman & Honorary Secretary

Mr. Chintan ShahPresident and Head (SBD)Suzlon Energy Limited, Pune

Executive Committee Members

Mr. Madhusudan KhemkaManaging DirectorRegen Powertech Pvt. Ltd., Chennai

Mr. Ramesh KymalChairman & Managing DirectorGamesa Renewable Pvt. Ltd., Chennai

Mr. Devansh JainDirector, Inox Wind Limited, Noida, U.P.

Mr. Ajay MehraDirector, Wind World India Limited, Mumbai

Mr. Hemkant LimayeCommercial DirectorLM Wind Power, Bengaluru

Secretary General

Mr. D.V. Giri, IWTMA, Chennai

Associate Director and Editor

Dr. Rishi Muni Dwivedi, IWTMA, Chennai

2 Indian Wind Power June - July 2016

Dear Readers,

Greetings from IWTMA!

15th June 2016 was celebrated globally as a Global Wind Day. IWTMA took part in a symposium and took the opportunity to announce “Windegy India 2017”, an International Conference and Exhibition proposed to be held in Delhi in January 2017. A brochure for the said Conference was released at the hands of Ms. Varsha Joshi, Joint Secretary, Ministry of New and Renewable Energy (MNRE), Government of India.

Windergy India 2017 is being organized by IWTMA in partnership with Global Wind Energy Council (GWEC), Brussels. This will be a unique event as “For the Industry and by the Industry”. The tagline to the conference is “Wind Power Forever”, which is appropriate to the nature’s gift of Wind to the Mankind. The theme is also equally appropriate as “Wind: Destination India” which compliments Indian Wind Industry’s contribution to “Make in India” with 75% localization and thus providing boost to the rural employment and the rural economy.

We take this opportunity to invite all our leaders to be part of this big event for the concern of the Mother Earth.

The Government has come out with a draft National Wind-Solar Hybrid Policy for promotion of renewable energy sector and there is a proposal to add 10GW of such hybrid capacities by the year 2021-22. This will help to promote a large grid connected Wind-Solar PV System for optimal and efficient utilization of transmission infrastructure and land.

There is an old saying that in a wind turbine “GEARBOX” is the heart and the Controller (computer) is the brain. We are dedicating the 14th issue of the Indian Wind Power magazine to the theme of Gearbox and its importance for the wind power generation.

We have posted six articles from gearbox manufacturers, research institutes and service engineers on the subject. We do hope that the readers will find the articles interesting and contents worth sharing of knowledge.

As, I conclude, IWTMA took a back stage in the social media promotion of www.windergy.in to promote wind energy as the dominant source in renewable energy. We invite readers to join and follow us at our Windergy Facebook and Twitter accounts.

Your feed back is valuable to us and we look forward to your suggestions to help us in constant improvement. Let us make substantive efforts by enhancing the capabilities of our members for the cause of Wind Energy in the country.

Regards,

Sarvesh KumarChairman

“Everything comes to us that belongs to us if we create the capacity to receive it”

- Rabindranath Tagore

From the Desk of the Chairman - IWTMA

3Indian Wind PowerJune - July 2016

Introduction

This paper discusses the configuration and design requirements for the major components used in the manufacture of a wind turbine gearbox.

The power from the rotation of the wind turbine rotor is transferred to the generator through the power train, i.e. through the main rotor shaft, the gearbox and the

high speed shaft, as shown in the image with the components of a wind turbine.

Gearbox consists of various components such as gears, bearings, shafts, planet carrier, torque arm, housing, etc.

Power Curve

The power curve is a key concept for understanding the efficiency of wind turbines. The power curve of a wind turbine is a graph that indicates how large the electrical power output will be for the turbine at different wind speeds.

Cut-in-Speed

The speed at which the turbine first starts to rotate and generate power is called the cut-in speed and is typically between 3 and 4 metres per second.

Rated Output Power and Rated Output Wind Speed

As the wind speed rises above the cut-in speed, the level of electrical output power rises rapidly as shown.

Wind Turbine Gearbox

Parthasarathy N Head, Driveline Engineering Romax Solutions Pvt. Ltd.

Platinum Towers, Old Trunk Road Pallavaram, Chennai – [email protected]

Stephen Brown, VP, Engineering Romax Technology Limited

Romax Technology Centre, University of Nottingham,NG7 2TU, UK

[email protected]

However, typically somewhere between 12 and 17 metres per second, the power output reaches the limit that the electrical generator is capable of. This limit to the generator output is called the rated power output and the wind speed at which it is reached is called the rated output wind speed.

Cut-out speed. As the speed increases above the rated output wind speed, the forces on the turbine structure continue to rise and, at some point, there is a risk of damage to the rotor. As a result, a braking system is employed to bring the rotor to a standstill. This is called the cut-out speed and is usually around 25 metres per second.

Indian Electric Grid connectivity: 690 V AC- 50 Hz

Major Functions of a Gearbox

The turbine is designed based on the following:

² Rotor speed, which is dependent on wind conditions, efficiency of blades, cost of blades, etc.

² Generator speed which is dependent on electrical frequency in that country, generator efficiency, cost of generator, etc.

Gearbox must make up the rotational speed difference between rotor and generator. This difference is called the ratio. For example, the rotor turns at 1 rpm (revolutions per minute) but the generator needs to turn at 100 rpm.


So the gearbox needs to have a ratio of 100 to 1 (or 100:1 as it is sometimes written).

Two stage medium speed gearbox (250kW) will have ratio of about 1:36 and Three stage gearboxe (750kW and above) will be around 1:105.

² Change Speed and Torque

The main purpose of a gearbox is to change the speed and torque of the rotor into something the generator can handle. Torque is a measure of the force needed to turn something. The rotor has a relatively very large torque, but moves very slowly. Most wind turbine generators need relatively a small torque to generate electricity.

² Change direction of rotation

Gearboxes can change not only the speed, but also the direction of rotation. This is important, as some generators can only turn in one direction, and most rotors only turn clockwise. The gearbox must be designed to turn the right way!

Two stage medium speed gearbox will have ratio of about 1:36 and Three stage gearboxe will be around 1:105.

How has the design of wind turbine gearboxes evolved through the years?

The wind industry has long debated the benefits of both direct drive (DD) and geared solutions for wind turbine drivetrains. DD solutions became increasingly popular following reliability challenges from MW-scale gearboxes. As it would currently seem, the industry is swinging toward geared solutions (high speed output-generator for smaller MW machines and medium speed for larger). This could be explained by improving reliabilities being enjoyed as well as better cost competitiveness, provided by geared drivetrains.

The predominant influencers on the design of wind turbine gearboxes have been (all driven by market requirements):

1. Cost and weight (being driven by commercial requirements of minimized LCOE)

Reducing design weight of gearboxes is deemed to ultimately reduce cost ($/Kg). This has driven the need for more optimized design through complex structural analysis, advanced optimum macro and micro gear geometry as well as bearing design through loading time series data.

2. Reliability (facilitating turbine level availability)

Drivetrain failure has long been plagued the wind industry and has driven up operational costs and damaged confidence in the technology. Feeding failure data and intrinsic intelligence into design has driven configuration changes as well as bearing selections. For instance, it was common practice to see spherical roller bearings used in mounting epicyclic planet gears in earlier wind turbine gearboxes which proved to be a significant failure source due to lack of intelligence and operational data.

Also a better understanding of aero-elastic driven loads (and effects) as well as transient events has allowed design considerations to accommodate in the gearbox ‘system’ through casing design, gear geometry and bearing selection. It is becoming a vogue point of discussion and consideration that actively controlling dominant aero-elastic loads through instrumentation and active pitch regimes will be a strong factor in next generation drivetrain design.

3. Noise requirements

With the increase in distributed generation requirements (siting turbines closer to the load), the market has driven the requirement for more stringent noise requirements. Given that wind turbine noise is typically emitted from both the blades and drivetrain, reducing gearbox noise through design is required. This has typically been implemented through gear macro and micro optimization again requiring the utilization of advanced software’s.

4. Since the industry is being driven by turbine level increased energy capture and resulting AEP (Annual Energy Production), bigger rotor diameters are increasing in popularities from OEM’s. The resulting load and torque increase, combined with lower weight and cost requirements are dominant driving factors in new product gearbox design.

Gearbox Mounting in Wind Turbines

² Modular system / Conventional gearbox

A modular system consists of rotor shaft assembly, gearbox, generator and possibly yaw drive, which are separately mounted


to a common bedplate. A modular system transfers the rotor support loads to the tower through bearings that are separate from the gearbox. With a modular system, an individual component such as the generator, gearbox or rotor shaft can be removed for repairs without disturbing the other components. The conventional gearboxes are classified into shaft mounted or foot mounted to the bed plate.

² Shaft mounted or 3-point support gearbox

Transmission on larger turbines are suspended on the main shaft, rather than mounted directly on to the frame of the turbine. Damping these shaft-mounted gearboxes allows the transmission to absorb fluctuations in torque caused by high wind speeds, introducing needed compliance into the drivetrain of big turbines. The torque arm is a structural component that attaches to the housing of a shaft-mounted gearbox and subjects the rotor shaft to a bending moment.

² Foot mounted or 2-point support gearbox

Foot mounted gearboxes require a coupling that provides torsional compliance and damping to reduce the rotor dynamic loads before they reach the gearbox. Stresses on the rotor shaft are reduced because there is no bending from a torque arm, or a gearbox weight, on the rotor shaft or rotor bearings.

Integrated System

In an integrated system, the gearbox housing provides the bearing supports for the rotor and interfaces for other components such as generator, brake yaw drives. Because of the rotor shaft is integral with the gearbox, the gearbox housing is subjected to rotor loads. Field problems with the gearbox, rotor shaft or rotor bearings usually require that the rotor blades removed and the generator, gearbox and the rotor shaft are removed as an assembly. The combined weight of the

assembly must be within the load capacity of normally available cranes and soil conditions. In large wind turbines, this can be major impediment to service.

Gearbox Interface Details

Interface is common boundary where direct contact between the gearbox and the other drivetrain & nacelle components in the wind turbine. The following are the major interface requirements the gearbox should meet:

² Rotor shaft interface (UW position) - bolted flange, shrink disc, bearings, taper joint

² Gearbox Mounts - Torque arm interface

² Pilot/Energy Tube - Upwind & Downwind electrical and hydraulic connection requirements

² HSS Connection - Coupling size and brake disc space requirement

² Brake - Disc size and position

² Lubrication, Heating & Cooling - Filtration Requirements, Offline, Online Filter & Heater, Oil Level Indicators: Visual; and electronic low level warning switch.

² Inspection Access

² Sensors - Temperature & Pressure, Accelerometers: Torque Arm, Rotor Bearing, 1st Stage, 2nd Stage, HSS & Bearings, Speed Sensors (Low & High)

Gear Train Configurations

² Simple Gear Train

The simplest type of gear train design transmits rotary motion through parallel shafts. The benefits of such a gear-train are its design simplicity and small number of operating parts. However the overall size and weight of the gearbox is considerably larger than an epicyclic to achieve the same gear ratio. Higher ratios can be achieved with simple gear trains compared with planetaries which are typically restricted to 1:5 because of packaging the sun and planets inside the ring gear.

² Epicyclic Gear Train

The epicyclic gear is a planetary gear arrangement consisting three or more gears meshed and rotating round a central sun gear. The planet gears are also meshed and rotate within


an internal ring gear. The planet gears are fixed to a planet carrier- crank arm designed to rotate on the same as the sun gear. Epicyclic gears have the advantage of being compact and lighted than the equivalent parallel shaft arrangement; however more parts are required to operate.

Planetary gear trains provide high power density in comparison to standard parallel axis gear trains. They provide a reduction volume, multiple kinematic combinations, purely torsional reactions, and coaxial shafting. Disadvantages include high bearing loads, constant lubrication requirements, inaccessibility, and design complexity.

Wind turbine gearboxes are either 2 stages or 3 stages based on the power rating of the turbine and the overall gear ratio required of the gearbox. The typical arrangements of the larger wind turbine gearboxes are shown in figures below.

² The smaller 2 stages gearboxes - both are parallel shaft stages.

² Larger 3 stage gearboxes - most of the arrangements –

* 1st Stage - Planetary

* 2nd Stage - Planetary or Parallel

* 3rd Stage - Parallel

Gear Types

² Spur Gears

Spur gears are the most common form of the gears found in gearboxes due to their simplicity. Spur gears are defined as have the length of their gear teeth parallel to the axis of the gear. Spur gear and gears mesh parallel to one another and their mating does not produce any axial thrust.

² Helical Gears

Helical gears are gears where the teeth follow a helix, or spiral, around the outside of the gear (a bit like a screw thread) the twist of the helix may be in either direction. Depending on the direction, helical gears are referred to as left- or right-handed. The helix angle is the angle at which the teeth twist relative to a spur gear.

Helical gears are generally quieter than an equivalent spur gear. This is because of the way that teeth come into (and leave) contact with each other. A disadvantage of helical gears is that the mesh forces have component acting along the shaft axis (where spur gears only produce radial and torsional loads). This means that gears will try to tip over relative to the shaft, move along the shaft, and the shaft itself will try to move along its axis relative to the housing. Design measures must be taken to control all these forces/movements.

Gear Rating

² Gear Rating Standards

The standards are intended to provide a reliable method of comparing gear capacities. Its aim to achieve a set of unified international technical standards. The national standards exists are AGMA, BS 436, DIN 3990 & ISO 6336.

² Gear Failures Modes

The ISO 6336 “Calculation of load and capacity of spur and helical gears” cover two failure models:

* Bending fatigue

* Contact Fatigue (pitting)

Nominal and Actual Bending Stress

The nominal bending stress is the maximum tensile root stress produced at the tooth-root when an error-free gear pair is loaded by the static nominal torque.


The actual bending stress is the nominal bending stress multiplied by certain factors that increase the stress. These take into account:

² The application

² Dynamic effects

² Alignment

² Tooth spacing errors

σF = σFO . KA . KV . KFBeta . KFAlpha

Where:

σFO - Nominal Bending stress

KA - Application Factor

KV - Internal Factor

KFBeta - Face Load Factor

KFAlpha - Transverse Load Factor

σFO= (Ft/bm). YF . YS . YBeta . YB . YDT

Where:

Fb - Nominal tangential load

bm - Face width

YF - Form Factor

YS - Stress Concentration Factor

YBeta - Helix Angle Factor

YB - Rim Thickness Factor

YDT - Deep Tooth Factor

Nominal and Actual Contact Stress

The nominal contact stress is the stress induced in flawless gearing at the pitch point by the application of static nominal torque.

The actual contact stress is the nominal contact stress multiplied by certain factors that increase the stress. These take into account:

² the application ² dynamic effects ² alignment ² tooth spacing errors ² lubrication

Common Gear FailuresSome of the most common gear failure mechanisms are

² Fatigue – Bending fatigue & Contact fatigue

² Scuffing

Gear Tooth Root BendingIf the maximum tensile stress at the root (in the direction of the tooth height), exceeds the permissible bending stress for the material, the root tends to break. Such phenomenon is called as tooth breakage and usually ends life of the transmission. Tooth root breakage is a fatigue phenomenon.

² Bending fatigue usually occurs in the tensile root fillet

² It usually takes many cycles to occur and often eye and marks are present

² Generally the break is smooth also indicating that some working of the fatigued surfaces has occurred

² Notches in fillets, heat treatment cracks and misalignment can often dictate where the breakage will occur

According to IEC 61400-1:2005, minimum required safety factor against tooth breakage is 1.45.

² Gear tooth Contact Fatigue (Pitting)

If limits of the surface durability of the meshing flanks are exceeded, particles will break out of the flanks, leaving pits. Such phenomenon is called pitting. It is treated as a fatigue problem.

² Contact fatigue is often termed pitting

² It is caused by the cyclic surface and subsurface stresses


² If the loads are high enough and cycles repeated enough small pieces of material fracture from the tooth surface

² It can be of 3 types

* Initial pitting (corrective pitting)

* Destructive pitting

* Spalling ( Very large in diameter)

According to IEC 61400-1:2005, minimum required safety factor against pitting is 1.2.

² Gear Scuffing

Scuffing is severe adhesive wear on the flanks of gear teeth. The adhesive wear is a welding and tearing of metal surface by the flank of the mating gear. It occurs when the oil film thickness is small enough to allow the flanks of the gear teeth to contact and slide against each other. Scuffing is not a fatigue phenomenon and it may occur instantaneously. The block’s concept of moving contact zone in machine elements is the basic for scuffing risk evaluation.

Shafts

Shafts shall be designed to adequately withstand the internal loads (generated be the gear meshes) and the external loads. Both the strength and the stiffness of the shafts are important. Adequate shaft strength will prevent fatigue or plastic deformation, while adequate stiffness will maintain gear and bearing alignment.

Housing, Torque Arm & Planet Carrier

The complex shape of the gearbox housing, torque arm and planet carrier usually requires that it be designed using finite element methods, FEM. It is especially important to ensure that the housing deflection caused by installation or operation does not misalign the gears. In integrates gearbox, the rotor shaft integrated with the gearbox, the gearbox housing is subjected to rotor loads. The housings are designed to both static loads and fatigue loads typically for a 20 years period.

Bearings

Permanent deformation appears in rolling elements and raceways of rolling bearings under static loads of moderate magnitude and increase gradually with increasing load. Bearing shall be designed for design life of the wind turbine. Basic functions of the bearings are:

² To allow a shaft to rotate and transmit power in a controlled manner for a given lifetime

² Not used in isolation, but part of a system comprising of a power-transmission-element, shaft, bearing and housing

² Be capable of carrying the loads imposed on it by the system

² Must also survive the displacements imposed by the system on its internal elements and maintain lubrication

² Generally also required to help control the displacements and tilts at the primary element(s)

² Survive a given duty cycle of load-speed duration and operating temperature range.

Bearings Life Calculation

² ISO 281 Dynamic Load Rating C

* Load that 90% of similar bearings would survive for 1 million revolutions under ideal operating conditions

² Equivalent Dynamic Bearing Load P (P = X FR + Y FA)

* Where P is a wholly radial or axial equivalent dynamic bearing load

* Minimum load should be greater than 0.01C for balls and 0.02C for rollers

* Maximum load should be less than 0.5C or 0.5Co whichever is lower

² Bearing Life Lnm

Lna = a1. a2.a3 L10 L10 = (C/P)p

Lnm = a1.aDIN.(C/P) p

Where:

a1 is a life adjustment factor for a failure probability of n%

a2 & a3 are adjustment factors for material and lubrication conditions

aDIN is a modifying factor for cleanliness, lubrication and fatigue limit

p is a life exponent equal to 3 for ball and 10/3 for roller bearings

Lubrication System

According to IEC 61400-4: 2012 (wind turbine design

specification of gearboxes), minimum quantity of oil in the

lubrication system should be:

Qoil = 0,15 . Pel + 20

where

Qoil is recommended oil quantity, in litres;

Pel is rated power of wind turbine, in kW.

This recommendation is based on experience with typical multistage gearboxes up to 2 MW where the gear housing forms the oil reservoir. Therefore, the minimum oil quantity should be reviewed if the design is not a multistage gearbox, is

larger than 2 MW, or uses a separate reservoir.


The oil level should be designed to minimize churning while providing adequate lubrication to all bearings and gears. The gear housing should have troughs to capture the oil flowing down the housing walls, channelling the oil to the bearings. Splash systems shall have an offline filtration system to control contamination and prevent the distribution of particles to critical gear and bearing surfaces. The offline filtration system shall be designed to maintain an oil cleanliness level one class better than the assumption made in bearing life calculations.

Gearbox Specification

² Rated Input Power ² Rated Input RPM ² Output RPM/ Generator RPM ² Direction of Rotation of Rotor (Gearbox I/P) ² Direction of Rotation of Generator (Gearbox O/P) ² Target Ratio ² Installation angle on drivetrain ² Gearbox Maximum weight (Dry & wet) ² Interface dimensions ² Type of lubricant ² Gearbox life time & Duty cycle ² Certification targets ² Survival & Operating temperature range (inside nacelle &

ambient) ² Ambient Humidity ² Onshore or Offshore

Gearbox Prototype TestFull scale testing has had a strong presence in the wind industry for some time and has been driven by certification agencies to make a requirement for Type Certification to validate design. It has also been used extensively are a compliance validation following a rebuild of a gearbox that has already been in service.

The benefits of full scale testing as strong and could not be detracted from, however it is recognized that it does have restrictions. Real operational loading is not accounted for other than torque so it cannot be a definite test for reliability. The industry is seeing 3 & 4 DOF test rig’s emerging that provide a close-to realist test.

Testing will always play an important role in the wind industry because of the costs associated with failure in operation, particularly offshore.

During the complete run-in test the torque, sound, vibration, oil cleanliness, oil pressure and temperature of bearings and lubrication oil must be continuously monitored and recorded. This is done while operating the gearbox at rated speed and increasing the load in steps of 20% until maximum load is achieved. Measurements are taken each step increase. After testing the gearbox is stripped and all parts are examined. The gear teeth are coloured with red or blue dykem to check the contact patches.

Conclusion

Wind turbine gearbox is a critical component in a wind turbine and international wind turbine design standard IEC 61400-1, defines gearbox as a class 2 component whose failure may lead to the failure of a major part of a wind turbine. Hence, the application of gearbox in a wind is a demanding one that requires careful consideration of the load spectrum to ensure that the gearbox has adequate load capacity and is within constraints on size and weight.

References:

1. IEC 61400-1, Wind turbines – Design requirements.

2. ISO 81400-4, - Wind turbines – Part 4: Design and specification of gearboxes.

3. ISO 6336-2, Calculation of load capacity of spur and helical gears – Part 2: calculation of surface durability (pitting).

4. ISO 6336-3, Calculation of load capacity of spur and helical gears – Part 3: calculation of tooth bending strength.

5. ISO/TR 13989-1, Calculation of scuffing load capacity of cylindrical, bevel and hypoid gear – Part 1: Flash temperature method.

6. ISO 16281. Rolling Bearings – Dynamic ratings and rating life.

The theme of the next issue ofIndian Wind Power is

"Human Resources in Wind Power Industry".We invite relevant articles to the theme. We solicit your cooperation.

Editor

Theme of the Next Issue

National Institute of Wind Energy – 2nd Wrapper

RRB Energy Limited – 5

SKF – 11

Bonfiglioli Transmissions (Pvt.) Ltd. – 17

Gamesa Renewable Pvt. Limited – 20-21

LM Wind Power – 25

Suzlon – 29

Windergy India 2017 – 33

NGC Transmission Asia Pacific Pvt Ltd. – 37

Swancor – 3rd Wrapper

Regen Powertech Private Limited – 4th WrapperAd

ve

rtis

em

en

ts


Abstract

This article gives an approach to estimate the fatigue life of gears which undergoes the HALT - Highly Accelerated Life Testing, in a back-to-back gearbox test rig set-up. This accelerated life testing method is used to simulate the few years or required 20 year life of gearbox components in short duration of testing, by over- stressing the gearbox components in controlled manner to induce failures during the test. This article will be useful to the gearbox designers and quality inspectors in the wind turbine applications.

Keywords

Wind turbine gearbox, Wind loads, HALT Test, Back-to-back gearbox test rig, Load spectrum, Fatigue life

Introduction

Wind is a vital source of clean, green and renewable energy. Wind energy has been the fast growing source of electrical power, to meet the growing demands of the world. The kinetic energy of the wind is converted to electrical power in a wind turbine generator using a speed increaser gearbox.

Quality requirements are very high for wind turbine gearboxes due to an expected lifetime of 20 years. The assumptions made during the design of the newly developed gearboxes and their suitability to use in nacelle over the tower top of the turbine are verified through prototype tests at a suitable test bench by measuring the bearing temperatures, sound, vibration behaviour and inspecting the gear contact patterns.

HALT

Highly Accelerated Life Testing (HALT), is used to simulate the 20 year life of gearbox components in short duration of testing, in a back-to-back gearbox test rig set-up, by over-stressing the gearbox components in controlled manner to induce failures during the test. The purpose of applying over load in HALT is not to verify the extreme stress limits at which the gearbox component will fail, but to accelerate the time-to-failure.

Overloads, approx. closer to 150% to 200% of nominal torque has been applied during HALT, such that the weakest elements of design has been exposed, rather than likely facing the same failure after months or years of normal operation in turbine.

Major test function of the back-to-back test rig is to validate:

² fatigue strength ² overload strength ² gear-mesh contact patterns ² oil cleanliness ² gearbox efficiency ² oil and bearing temperature ² structure-borne/airborne noise ² gearbox vibrations

Figure 1: back-to-back test bench schematic. (Courtesy: www.bepco.com)

Estimating Fatigue Life of Gears in HALT Test for Wind Turbine Gearboxes

M. Mahendran, Head – Engineering, Shanthi Gears Limited, C-Unit, Avinashi Road, Muthugoundenpudur Post, Coimbatore - 641 406, India

[email protected]

Figure 2: Rotor coordinate

system (Courtesy: GL 2010)


Wind Turbine Loads

Wind turbine manufacturers predict design load cases, by using aero-elastic wind turbine codes/simulation software as specified by standards and guidelines. The fatigue evaluations are based essentially on the time history of the rotor shaft torque, hence loads will vary with wind turbine classes and site specific wind velocities. This data also contains the dynamic load transients in gearbox during “grid loss” and load amplifications during “emergency stop” for calculating static safety of gearbox components.

Time at level per bin [hour] against MXHSR [kNm]

MXHSR [kNm] 25.5 28.5 31.5 34.5 37.5 40.5 43.5 46.5 49.5 52.5 61.5 64.5 67.5 70.5 73.5

Rotor speed [rpm]

18.6211 0.007 0 0 0 0 0 0 0 0 0 0 0 0 0 0

19.5761 0.309167 0 0 0 0 0 0 0 0 0 0 0 0 0 0

20.531 0.154972 0.175583 0 0 0 0 0 0 0 0 0 0 0 0 0

21.4859 0.014778 0.246361 0.084389 0 0 0 0 0 0 0 0 0 0 0 0

22.4409 0.044333 0.014 0.260361 0.014 0 0 0 0 0 0 0 0 0 0 0

23.3958 0.022167 0.022167 0.035 0.239361 0 0 0 0 0 0 0 0 0 0 0

24.3507 0 0.044333 0 0.07 0.204361 0 0 0 0 0 0 0 0 0 0

25.3057 0.028 0.007389 0.036944 0.007 0.112389 0.154972 0 0 0 0 0 0 0 0 0

26.2606 0.042 0 0.029556 0.014778 0.021 0.105194 0.119972 0 0 0 0 0 0 0 0

27.2155 0.007 0.028 0 0.036944 0 0.021 0.105194 0.098972 0 0 0 0 0 0 0

28.1704 1.69687 0.042 0 0 0.044333 0 0.028 0.147583 0.056389 0 0 0 0 0 0

29.1254 4.41186 1.01812 0.035 0 0.022167 0.014778 0 0.049 0.133583 0.035583 0 0 0 0 0

30.0803 4.65733 4.41186 0.042 0 0 0.044333 0 0.007 0.07 0.133972 0 0 0 0 0

31.0352 96.5059 1.35749 3.06136 0.028 0 0 0.044333 0 0.021 0.091 0 0 0 0 0

31.9902 683.614 10.264 2.03624 1.74587 0 0 0.022167 0.022167 0 0.021 0 0 0 0 0

32.9451 1389.8 149.898 1.75184 4.08648 0.028 0 0 0.044333 0 0 0.028389 0 0 0 0

33.9 2260.28 729.221 38.9627 2.85871 3.77511 0 0 0 0.044333 0 0.147778 0.007194 0 0 0

34.855 1099.43 1764.77 244.143 7.59621 2.60671 2.75699 0 0 0.014778 0.036944 0.077 0.147972 0 0 0

35.8099 407.201 2238.8 816.709 98.3136 5.53081 2.40016 2.03624 0 0 0.022167 0.007 0.084 0.133972 0 0

36.7648 76.2182 1247.89 1518.18 311.066 67.2273 13.2848 7.2844 4.86281 1.07166 0.177419 0 0.007 0.091 0.133972 0

37.7197 12.227 481.938 1837.45 958.284 268.657 86.4935 35.3288 12.8333 9.07067 4.56083 0.120006 0.004031 0 0.084 0.168972

Figure 3: Main Drive Gearbox (sample) Loads, Specified in Time Domain (hours) against various Torque and Speed Levels

Load Spectrum

Load spectrum is used to compute the strength calculations of gear pairs and gearbox components as specified in International standards like GL, IEC, ISO6336, AGMA 6006 to find the safety factors, service life and permissible power rating of gearboxes. A load spectrum is a “simulated” or “assumed field loads” consists of the frequency, speed and power or torque data. The data is compiled for all design/assumed range of operational speeds and torque range, with estimated running hours for each bin.


bin no.

torque (kNm)

hours

1 135 0.00050

2 125 0.00102

3 110 0.00130

4 109.5 0.00202

5 106.5 0.00500

6 103.5 0.00700

7 100.5 0.01000

8 97.5 0.35022

9 94.5 81.4

10 91.5 5367.9

11 88.5 13733.7

12 85.5 7207.9

13 82.5 4916.8

14 79.5 4386.8

15 76.5 4066.9

16 73.5 3651.0

17 70.5 3502.2

18 67.5 3600.1

19 64.5 3050.7

20 61.5 3302.7

bin no.

torque (kNm)

hours

21 58.5 3113.2

22 55.5 2733.7

23 52.5 2828.6

24 49.5 2937.9

25 46.5 2879.9

26 43.5 2953.3

27 40.5 3131.8

28 37.5 3845.6

29 34.5 5307.0

30 31.5 6067.8

31 28.5 6736.5

32 25.5 6043.7

33 22.5 5899.8

34 19.5 7384.8

35 16.5 6934.9

36 13.5 5318.6

37 10.5 6712.2

38 7.5 9468.9

39 4.5 7988.0

40 1.5 15260.0

total hours 170454

Figure 4: Consolidated LDD in 40 Bins with Corresponding Torque and Occurring Hours (sample) Data

Fatigue Life Calculation

The calculated bending or pitting fatigue life of a gear is a measure of its ability to accumulate discrete damage until failure occurs, based on ISO 6336. (Refer respective standards for detailed explanation on rating theory.)

Figure 5: Equations used for Contact and Bending Stress Calculations (Ref: ISO 6336)

Calculated service life of gearbox is based on the theory that:

² every load cycle (every revolution) is damaging to the gear.

² the amount of damage depends on the stress level.

² damage can be considered as zero for lower stress levels.

The fatigue life calculation is mainly based on linear damage accumulation method Palmgren-Miner rule/Corten-Dolan/Haibach, that requires:

² the stress spectrum

² material fatigue properties

² a damage accumulation method

Failure could be expected U=1.0 or above 1, according to the SN curve established for the material and stress spectra for each load level acc. ISO 6336-part 6.

Gearbox Spec. Technical Data (ref.*):

Rotor Nominal Power 400 kWRotor Speed 40 min^-1Rotor Nominal Torque 95.5 kNm

LSS IMS HSSType of Gearing HELICAL

mn=7HELICAL mn=5

HELICAL mn=3

CD 450 320 225Teeth on Wheel z2 95 95 109Teeth on Pinion z1 27 27 36Ratio 3.52 3.52 3.02

Nominal Speeds (RPM)Input side of stage 40 140.8 495.6Output side of stage 140.8 495.6 1500

Nominal Torque (kNm)Input side of stage 95.5 27.13 7.7Output side of stage 27.13 7.7 2.54

(* assumed tooth data is used here to explain concept.)

Figure 6: Gearbox Data (Sample)

Life Estimation using Standard LDD

By using the commercially available gear calculation software KISSsoft /KISSsys, it is possible to compute the calculations quickly, by using the LDD derived for the specified loads by the wind turbine manufacturer.


Figure 7: KISSsoft User Interface with defined Load Spectrum

The service life of the gears is calculated with the actual LDD for the required safety factors on tooth root and tooth flank. It is based on the S-N curve (woehler curve) of the miner’s type considering case carburised material with number of load cycles 5 X 10^7 cycles for pitting and 3X 10^6 for tooth root strength.

Figure 8: Damage Calculation with Specified Loads given in LDD

Figure 9: S-N Curve Plotted for Root Strength, with Case Carburised Material and Specified LDD


Life Estimation using HALT Load with LDD

Similarly the service life of the gears is calculated with the HALT loads, and the LDD is derived accordingly to get the required safety factors on tooth root and tooth flank.

Figure 11: Loads on HALT Test with 120% Load SetFigure 10: S-N Curve Plotted for Flank Safety, with Case Carburised Material and Specified LDD

Figure 12: KISSsoft Calc. with HALT Loads


Bonfiglioli is a leading provider of complete packages for the wind industry that seamlessly control energy generation, from rotor blade positioning with a pitch drive to nacelle orientation with a yaw drive. Working closely with customers, Bonfiglioli designs and manufactures a series of specialized wind turbine gearboxes and inverters that deliver reliable, superior performance.

Complete Solutions forYaw & Pitch Control

Bonfiglioli Transmissions (Pvt.) Ltd.PLOT AC7-AC11, SIDCO Industrial EstateThirumudivakkam, Chennai - 600 044, INDIAPh: +91(044) 24781035 - 24781036 – [email protected] • www.bonfiglioli.com


Figure 13: Life/Damage Estimation with HALT Loads Figure 14: S-N Curve Plotted for Root Safety, with Case Carburised Material and Specified HALT Loads

Figure 15: S-N Curve Plotted for Flank Safety, with Case Carburised Material and Specified HALT Loads

The damage in HALT is different for root and flank. Also, the damage in HALT for each stage of gearbox (LSS/IMS/HSS) is separate.

Figure 16: Damage % Calculation on Basis of HALT Duration h=350 hrs.

Damage CalculationLife consumed in HALT

Damage due to HALT = U_HALT

Total permissible damage U_total = 1.00

Life Estimated under LDD= = 20 years

Life consumed in HALT = U_HALT X 20 years

Life Remains after HALT U_rest = U_total ‐ U_HALT

Damage is proportional to life, so, one unit of damage = 20 years

Hence, remaining life L_rest = 20years ‐ life consumed in halt

= 20years ‐ ( U_HALT x 20 years)

= 20years x (1‐ U_HALT)


Damage also can be calculated on basis of system & individual component’s service life.

Figure 17: Damage Calculation on Basis of System/Individual Service Life

Limitations

There are different opinions with gear manufacturers and design experts about the HALT test, but only continual experimentation can prove the correct one after some time. Some of the expert opinions are:

² The load spectra is not being very informative in many areas.

² The damages originate in very few spectrum steps for highly stressed gears.

² The damage relevant steps for the bearing lay somewhat lower than for the gearing due to smaller S-N curve slope.

² Possible gaps in Material quality, process variations from design considerations.

² Need several calculations with different spectrum for changed tower height, blade length, different installation places.

² Exact prediction of field loads and simulation of dynamics in test bench is not easily achievable.

² For scuffing, the fatigue calculation method is not applicable (because scuffing is not a fatigue effect) and that if torque in HALT is high, scuffing may be a limiting factor.

² For Micropitting, no HALT is possible as it is not yet clearly understood how LDD affects Micropitting / how Micropitting depends on no. of cycles.

² Failure is at U=1 for gear rating standards but research suggest that U=0.4 may be more realistic.

Conclusion

HALT is a useful technique to ensure the higher reliability of the product and it enables faster time to market of multi-MW WTG gearboxes.

References

1. ISO 6336:2006 Part 6: Calculation of service life under variable load

2. Static and Fatigue Calculations of Wind Turbine Gearboxes -Dipl. Ing. ETH HanspeterDinner

3. Dr. Kissling, & H. Dinner, Lecture Notes, India - Gear Rating and Wind Turbine gearboxes

4. Mr. H. Dinner & Dr. Giger - Lecture Notes -Windmill gearbox Technologies & KissSoft Training, CWET, Chennai, June-2007

5. KISSsoft software 03-2015, www.KISSsoft.ch

6. Germanisher Lloyd (GL) Guideline for the Certification of Wind Turbine Edition 2010

7. Advances in wind turbine and components testing- IEA R&D Wind Task 11 -Topical Expert Meeting proceedings Feb. 2012

Note: Great care has been taken in the compilation of this article. This article is intended for use by persons at their sole discretion and risk. The author, editor or publisher is not liable for special, indirect or consequential damages resulting from the use of this material.


Securing Reliability for Gearboxes of Giant Multi-Megawatt Turbines

The trend in the wind energy industry across the world is clear in their goal to lower the costs of energy generation, wind IPP’s and wind turbine manufacturers strive towards larger turbines with higher megawatt classes. For these next-generation turbines megawatt rates of 3 to 5 megawatt for onshore and 6 to 8 megawatt for offshore turbines are now considered state-of-the-art. Market trends show that the industry demand is increasing for even higher classes in the next years. The technological challenges going along with this development are huge, not least for gearbox manufacturers.

Simply stated, the function of a wind gearbox is to transform the slow speeds of the wind rotor into the faster rotations that the generator needs to generate electricity. In this process, of course, also the high input torques and loads coming from the rotor need to be picked up and transformed. Rotor diameters of 150 meter or more for giant offshore turbines result in enormous torques and loads for the drive train. To answer the requirements involved it is not possible to simply upscale the existing concepts. Gearbox manufacturers have to further work on their portion to reduce the Levelized Cost of Energy (LCOE). While developing new solutions the questions to be answered are: ‘How will the bigger input loads affect the drivetrain?’ and ‘How will gearbox manufacturers secure the reliability of their products?’

New Challenges

Technology for respective gearboxes in the multi-megawatt classes is constantly developing and prototypes of above 6 megawatt are in field testing operation. Delivering gearboxes of close to 90 tons in series has specific challenges for supply chain and engineering. All laws of similarity do have to be extrapolated from the current fleet. To prove that these extrapolations are viable and the quality of the products can be ensured extensive simulation and testing have to be conducted at every stage of the development process for product, single parts and raw materials.

Nowadays common gearbox designs can be classified into high-speed and medium-speed drivetrain concepts. For years high-speed planetary helical gearbox concepts consisting of one or two planetary gear stages with helical gear stages have been the industry

standard. In recent years this has been expanded by medium-speed drivetrains that combine a two-stage planetary gearbox with a generator to one product. High-speed gearboxes score with their high-torque density and proven reliability. Through the combination of gearbox and generator medium-speed drivetrains (also called hybrid drives) deliver the highest overall efficiency while being very compact and light weight.

Medium-Speed Drivetrains

The overall concept design of current multi-megawatt machines shows a development towards medium-speed geared drive trains. Let us therefore have a closer look at these developments. Recent turbine concepts of leading wind turbine manufacturers show for example that they are no longer using the conventional 3-point or 4-point suspension design but flange connections between main frame and drivetrain. While deflections for standard concepts are widely understood the newer concepts have to be carefully evaluated and significant influences like non-linear scaling effects have to be considered. Lowering the lifetime or levelized cost of wind energy (LCOE) as key motivation, the focus is on improving wind turbine drivetrain efficiency and reliability while lowering drivetrain component costs. Specific benefits in particular for offshore applications include tower-head weight reduction and compactness, allowing easier encapsulation.

All hybrid drive concepts use a coaxial gearbox design, which results in eliminating the third, helical gearbox stage. Removing this high - speed stage has three main effects. First, increased reliability as the high - speed bearings are main contributors to gearbox failures (see Make: Global Wind Turbine Trends 2015). Second, increased efficiency of the gearbox as roughly one- third of the gearbox losses are due to the high speed stage. And, thirdly, a lower generator speed (going along with a higher generator torque), as the overall gearbox ratio is reduced by the ratio of the high speed stage.

These assumptions have been proven by 3MW wind turbines with hybrid drives which have been operating for almost three years now. After a run-in period with technical availability

Dr. Andreas Klein winergy - Head of

Engineering ak.klein@

siemens.com

Matthias Deicke winergy - Head of Electrical Systems matthias.deicke@

siemens.com

Dr. Thomas Meyer winergy - Manager New

Bearing Technologies thomas.mrts.meyer@

siemens.com

Winergy - Siemens AG, Am Industriepark - 2, 46562, Voerde, Germany

Winergy HybridDrive

Winergy Gearboxes


at approx 90%, the two turbines have been performing in the 97% to 100% range - industry standard for well-maintained wind turbines. There has not been a single issue with the gearbox-generator unit.

The change in design concept also leads to a shift of elasticity from HS-coupling and torque-support to the input shaft of the gearbox, thereby influencing the dynamic behavior of the entire drivetrain. To avoid unexpected side-effects in the powertrain multibody dynamic models are established in cooperation with the OEMs. Characteristic gear parameters that are modulus reach new regions in respect of weight and dimensions. This leads to a significant change in process parameters for gear manufacturing, heat treatment as well as gearbox assembly and logistics.

Journal Bearings

As gearbox manufacturers strive towards maximum reliability and low life-cycle costs, it is also worthwile to have a look at the bearings. They belong to the parts of wind gearboxes that are exposed to high loads in operation and therefore have a significant impact on the overall gearbox reliability. As journal bearings have proven their advantages in several other heavy industries, gearbox manufacturers started to develop the technology as an alternative to common roller bearings in 2010.

The development and design of bearings in windpower gearboxes represent an increasing challenge as gearboxes get larger and their load and deformation conditions change accordingly. Positive experience made with journal bearings in industrial applications can be used to good effect in the windpower sector, if windpower-specific limiting conditions are taken into consideration. The high loads at low sliding velocities are a particular example here.

To validate their suitability for operation in wind power gearboxes, journal bearings were subject to exhaustive tests both on test-rigs and in the field. Test-rig tests have confirmed journal bearings can be operated hydro dynamically in wind power gearboxes without causing wear. This finding is supported by the successful field operation of a prototype fitted with journal bearings that has been faultlessly in operation for two and a half years in a Vestas V90 turbine. Journal bearings behave very well during operation in wind power-specific conditions. Also special operating conditions like prolonged idling and emergency braking are borne by journal bearings without any problem. It was also found that wind power gearboxes fitted with journal bearings show low sound radiation because of the greater damping capacity of hydrodynamic journal bearings.

All these developments have not reached the highest level yet. In some aspects the current gearbox sizes are exploiting the limits of today’s manufacturing possibilities. Even larger turbines already appear at the horizon. Therefore, also in the future the market requires for gearbox designs capable of transferring even higher loads and gearbox manufacturers are already working keenly on these concepts.

Planetary carrier with journal

bearings

Wind Industry News:

• Merger of Gamesa and Siemens's Wind Power Business

Gamesa and Siemens have signed binding agreements for the merger of Siemens's wind power business with Gamesa. The Indian market is one of the key assets of Gamesa and will continue to remain so under the new merged company.

• SunEdition to Sell Wind Power Plant in Andhra Pradesh

SunEdison is close to an agreement with Sitac RE to sell 24 MW wind-power plant in Andhra Pradesh. The project has room for another 50 MW and is likely to expanded by Sitac RE.

• Gamesa is to open a Blade Factory in Andhra Pradesh

Gamesa is to open a blade factory in Nellore, Andhra

Pradesh in India to build G114 2.0MW class S units,

custom designed for the local market. The facility

will have the capacity to manufacture 250 blades or

500MW a year and will be inaugurated in September

and will employ 400 people.

• Amended Guidelines for Installation of Prototype

Wind Turbine Models

MNRE has issued guidelines for installation of

prototype wind turbine models on 22.05.2012. Further

amendments to these guidelines have been issued on

20.09.2012 and on 01.06.2016.

• Government to Electrify All Villages by 2016

Power Minister Sri Piyush Goyal, during 2 days

meeting of the State Power Ministers has said that the

Government will electrify all un-electrified villages by

2016 barring areas affected by Maoist insurgency.

Sn

ipp

ets

on

Win

d P

ow

er

CORRIGENDUMPlease refer to Indian Wind Power,

April - May 2016 issue Page - 36 and 37.

The captions of Figures 7 and 9 got interchanged. Please read accordingly.


Energy Management System - ISO 50001 ‘A Commitment of Optimum Energy to Customer’

Dr. Sanjiv Kawishwar - Sr VP , ReGen Powertech, India

Dear Reader,

It is our endeavour to make IWTMA magazine Indian Wind Power, “THE MAGAZINE” for the Indian Wind Industry. Your feedback on the general impression of the magazine, quality of articles, topics to be covered in future, etc. will be of immense value to us. We are thankful to your response. Kindly address your mail to

"[email protected]".

Thank You,

The Editor - “Indian Wind Power”

Indian Wind Turbine Manufacturers Association 4th Floor, Samson Tower, 403 L, Pantheon Road, Egmore, Chennai - 600 008. Tel: 044 43015773 Fax: 044 4301 6132 Email: [email protected]

² It is the endeavour of every renewable energy company to

maximize energy generation as well as to reduce energy

consumption.

² Implementation of Energy Management Systems (EnMS)

and certification to ISO 50001 helps company to

achieve the objective of optimum generation and energy

conservation.

² ISO 50001certification helps to regain the confidence of

Investors and Financial Institutions in wind and solar energy

projects.

² It is the most pertinent standard for renewable energy

companies today which demands demonstration of

enhanced energy performance on a continual basis

according to stringent specifications.

² EnMS Standard requires optimization of specific energy of

each component/process/ system of wind/solar park and

hence effectively improves energy performance.

² EnMS certification is an assurance to customers that

‘optimum energy will be generated for life time’ by the

wind turbines and also energy will be conserved in each

associated process.

² EnMS is ‘a long-term sustainable solution to customers

for optimization of energy in every process of generation

or conservation’ and a modern key to success in global

market.

² Commitment to optimize energy through certification

makes investor confident to get maximum returns.

² Implementation of ‘Energy Management Systems’,

improves the carbon footprint of the company even for

auxiliary processes other than electricity generation.

² When organisation implements ISO 50001 simultaneously

with the type certification, it helps to create systems which

generate optimum wind energy till life time.

ENERGY POLICY – A True Reflection of Vision and Mission

Energy policy reflects the passion of organization to generate

clean energy and commitment to enhance energy performance

of processes, products and services.

The focus should be on

Optimization of renewable energy output of wind / solar parks

on continual basis.

* Reduction of specific energy consumption.

* Compliance to legal and other requirements.

* Setting up and reviewing energy objectives & targets.

* Deployment of information and resources to achieve

objectives & targets.

* Use of energy efficient equipment designs and services.

* Promote awareness to conserve energy

We Need Your Feedback

www.indianwindpower.com


The prevailing trend within the wind industry towards powerful and reliable wind turbines, with high availability in challenging operating conditions, calls for proven and therefore reliable design concepts with a high power-to-weight ratio. In this way, an attractive balance in investment cost (capex) versus operational cost (opex) is attained, thereby contributing to overall cost of energy reduction of wind energy.

Gearbox companies spend considerable efforts to develop design concepts, which can be used as “building blocks” in order to establish a flexible product matrix for all common wind turbine platforms. This product portfolio can be seen as a matrix of torque scale versus drivetrain concept, where every specific customer concept is covered - from medium to high speed and from conventional to integrated design.

From High to Medium Speed

Generally, the gearboxes are designed in typical configurations of “1 planetary + 2 parallel stages” or “2 planetary + 1 parallel stage”. This configuration, in combination with the widely used Doubly Fed Induction Generators (DFIG), offer an overall drivetrain which is both proven in the field as well as cost optimised.

The recent development of medium speed gearboxes have also helped in developing integrated medium speed drives for wind turbines. The integration of main shaft, gearbox and in-line generator offer competitive advantages. Figure 1 shows representation of the gearbox concepts.

High Power-to-Weight Ratios

Generally, drivetrain optimisation is strongly driven by integration of its individual components. Therefore significant time, expertise and expenditure on research and development are spent on achieving high power-to-weight ratios. The power-to-weight ratio of a gearbox is important since weight reduction leads to a reduction in capex cost, and affects transportation, foundation and installation costs, as well as the cost of the accompanying tower.

The trend towards increasing power-to-weight ratios should be accompanied by risk reduction, assuring high reliability of the gearbox in the drivetrain. With increasing wind turbine power and increasing rotor diameters, gearbox torque increases more than linear. This is demanding for large size gearboxes.

Proven Bearing Solutions

Bearing technology in wind turbines and especially in the drivetrain is challenging due to the dynamic behaviour of the application. Typically, bearing configurations are designed in co-engineering with the leading bearing suppliers for optimal performance.

Furthermore, the bearing configurations are proven with dedicated tests on bearing arrangements under conditions which mimic the actual operational conditions in the application. By means of this test rig, which is the most advanced facility of its kind, we are able to test real size bearings in their actual arrangement as built in the gearbox, under representative wind turbine loading and environmental conditions. In this way bearing behaviour, as well as loadability of bearing assemblies, can be verified in order to proactively contribute to the design of robust bearing arrangements for new gearboxes. This continuously improves the reliability of selected bearing arrangements. The test algorithm translates a set of simulated wind loads (the typical input design load time series from customers) into a dedicated test programme. This test programme comprises equivalent load conditions to be applied in a reduced time frame on dynamic bearing test rig. A typical example of the dynamic bearing test rig available is as per Figure 2.

Also, new developments like integrated tapered planet bearings, where the outer ring of the tapered planet bearings has been integrated into the planet wheel offer compact solution. This solution reduces the number of components, thereby increasing robustness of the planetary stages.

Prove and Improve

In order to support the demand for both cost-competitive and high-quality, robust and reliable drivetrain solutions for any type

Competitive Gearboxes for Reliability

Sonja Goris, Innovation Manager ZF Wind Power Antwerpen NV, A Business Unit of ZF Friedrichshafen AG, Belgium

(ZF Wind Power’s Sonja Goris looks at reliable and competitive gearbox designs.)


of wind turbine, validated design concepts are key elements.

Such validated concepts serve as “building blocks” for advanced

gearbox solutions. The need for increased gearbox component

sizes - due to larger rotor diameters or increase in nominal

power – has to be anticipated by the gearbox manufacturer by

means of a step-by-step approach based on proven technology.

Advanced design concepts - thoroughly verified by means of

advanced test algorithms on test rigs emulating wind turbine

behaviour (ref. Figure 3) – help to prove and improve

performance and long-term durability of wind turbine

gearboxes. This is yielding an overall increase in the availability

of operational wind turbines, lowering operational costs to

reduce wind energy costs further.

Figure 1: ZF Wind Power’s Drivetrain and Gearbox Concepts

Figure 2: ZF Wind Power’s Dynamic Bearing Test Rig

Figure 3: ZF Wind Power’s 13.2MW Dynamic Test Rig


Abstract — The computer technology has been applied widely on mechanical engineering design and project management. For wind power industry, the computer technology is always applied by computation and simulation on wind turbine gearbox design. The professional computer software tools can simulate the actual running situations of the gear rating and transmission of the gearbox before manufacturing and prototype testing. This paper proposes the relevant analysis regarding computer technology application on wind turbine gearbox design, and presents the essential auxiliary function of computer simulation of some particular software tools for gearbox operation, gear rating and transmission drivetrain on wind turbine gearbox design.

Keywords — Wind power industry; Computer simulation; Gearbox operation; Gear rating; Transmission drivetrain

1. Introduction

The wind power is a kind of clean energy which will be applied worldwide in future. There are many global power generation enterprises and organizations have been cognizant of the importance and significance of wind power, and have started to develop wind power generation technology and constructed more wind power stations. The wind turbine is power transmission machinery, the integrated performance on efficiency and reliability of wind turbine should be determined by the functions of transmission parts. Consequently, the quality of design and manufacture of core parts such as gearbox, blades, pitch and yaw drivers, motor and so on are very important for wind turbine. In modern world, the mechanical engineering designers usually use computer software for complicated projects. The auxiliary design function of computer technology is really effective to improve design efficiency, and the design scheme and manufacture procedure of particular product can be optimized effectively with the help of computer technology.

It is widely known that the designers should apply various software tools to build part models, and then finish the whole project step by step gradually under the supports of various simulation and computation. For the particular application of computer technology on wind turbine gearbox design, the software package should include the functions which are computation, CAD drawing, CAE analysis, simulation, management and so on. Generally speaking, the most popular software tools for mechanical engineering with

outstanding reputations and widely application always has good data processing capability and computing speed, some professional modules for particular application, reliable and strict theoretical basis and friendly operational interface. For example: CATIA, AutoCAD, SolidWorks, Pro-Engineer, I-DEAS and so on are very popular CAD drawing software tools. ANSYS, Nastran, Hyperworks, ABAQUS, FE-Safe and so on are CAE software tools with wide application. For particular application on wind turbine gearbox design, UG, KissSoft, Romaxwind, MASTA and so on are professional software which are focus on gear calculation and gearbox design. For powertrain transmission simulation, ADAMS, Simpack, Recurdyn, Nucars and so on have good experience on dynamic analysis. The software tools mentioned above are all involved in wind turbine gearbox research and design. They are all reliable and accurate enough for wind turbine gearbox design and have collected valuable experience during past development.

This paper will propose and introduce the typical computer technology application on wind turbine gearbox design, which includes detailed function and effectiveness of computer simulation on gearbox system design, gear contact analysis and powertrain transmission. The three different kinds of software tools application and relevant principles of gearbox design will also be described.

2. Computer Simulation on Gearbox System

At the beginning of the design of wind turbine gearbox, it is primary to carry out relevant initial analysis on the performance and life of gearbox components such as gears, bearings, shafts and so on. The analysis results make sense base on the simulation of gearbox transmission system. The purpose of gearbox system simulation is to build integrated modeling of the gearbox which includes planetary gear systems and parallel gear sets, bearing groups, oil seals, lubrication and cooling system and so on. The analysis results which derive from the modeling must be reliable and practical for the particular project, and also can reflect the actual operating situation of the gearbox transmission system.

The professional software tools which can be used for wind turbine gearbox design must have the capabilities which are power flow simulation, gear and bearing calculation with comprehensive considerations, shaft strength calculation, and effective interface with other auxiliary software. Furthermore, it is certainly that the software must have good application and combination with various

The Computer Simulation on Wind Turbine Gearbox Design

Shigang Chen Gearbox Research Institute

Dalian Huarui Heavy Industry Group Co., Ltd., Dalian, China

Zheng Li Dalian Martitime University

Dalian, China


specifications and standards. The only designs which follow the relevant standards can be acceptable by qualification organizations and users.

Figure 1: Wind turbine gearbox system modeling

Figure 1 indicates the wind turbine gearbox system modeling which are simulated using professional design software tools Romaxwind and MASTA. The models include all of the gear components, shafts, bearings, couplings, connections and so on. The particular parameters and factors which will influence the performance of key components significantly such as gear quality grade, gear parameters, shaft dimension, bearing type selection, material properties etc. have been involved in and defined to conform with relevant specifications, design data and input load spectrum. The necessary analysis for gearbox system simulation should include following items:

² Gear strength calculation — to examine gear tooth static and fatigue bending and contact safety factors through power flow calculation. It is essential to carry out the calculation with the load cases which are rated load, extreme load and LDD.

² Bearing calculation — to examine the bearing operating life and the rate of damage. The results of bearing life must be more than 30,000 hours for general wind turbine gearbox design to ensure the bearing life is sufficient to conform to industrial standards.

² Strength analysis for shafts and connecting elements — to calculate the safety factors of transmission shafts and couplings such as interference fit and splines in order to analyze the strength of the components.

² Bolted connections calculation — to examine the reliability of bolted connections where are applied for wind turbine gearbox design.

² Housing and Planet carrier finite element analysis — to calculate the strength of housing parts and planet carrier more accurately using finite element analysis. Furthermore, it is also important to import finite element models of housing parts and planet carriers to the modeling of gearbox system to calculate the structure deformation more practically.

² Lubrication system Calculation — including the calculations regarding losses, oil cooler, oil heater, pressure and temperature measurement and so on to validate the performance of lubrication and cooling system.

Furthermore, another important purpose of gearbox system simulation is to carry out gear tooth micro geometry modification. The amount of modification should be applied to the modeling

to analyze the situation of gear contact. The results of contact pattern and transmission error can be worked out after calculations. The designer can optimize the position of contact pattern and average contact stress distribution by regulate relevant modification parameters. Figure 2 indicates the results of contact pattern which is exported from Romaxwind.

Figure 2: Contact pattern result

3. Computer Simulation on Gear Rating

The simulation of gear rating is a very useful auxiliary function of computing technology on gearbox design. The basic theory of modeling profile generation is analytical method, which means the mathematic formulas will be proposed to calculate the point coordinates in gear tooth profile, and then combines these points with many short beelines to generate particular tooth profile (multi-section lines method). This method derives from the principle of spur gear manufacture. In other words, the standard involute spur gear tooth profile is generated by certain gear cutting knife in actual manufacture. The gear tooth profile curve formula can be gained from the track of contacted points between gear tooth profile curve and knife curve. Consequently, the function of computer software is to simulate the path of manufacture knife tool, and generate the gear tooth profile curve automatically. The designers can obtain the detailed situation of gear rating and the particular performance results of gear pair during gear contact process with the help of computer software.

Generally speaking, it usually adopts finite element model of gear pair with the combination of CAD software tools. The gear tooth profile and particular geometry information of gears can be created as CAD drawings, and the expected results of necessary analysis regarding gear rating or gear tooth contact can be worked out using finite element method. It implies that the integrated process of computer simulation on gear rating can be divided as two parts: gear geometry creation and finite element analysis. The relevant software package should include CAD and CAE software tools for the simulation.

For gear generation, the completed profile of gear tooth should be generated respectively with the sections which are involute profile and root curve. The designers can calculate the coordinates of the points on gear tooth profile by a piece of C++ or Matlab program, and then connect these points together to generate integrated gear tooth profile using CAD software. Figure 3 illustrates the finish profile of gear in AutoCAD software, the gear geometry model will be used to build gear rating finite element model for further analysis.


The objective to build reliable finite element model is to simulate actual gear rating process. It is not only the first but also the most important step of the relevant research because the reliability of research model affects the accuracy of results. The factors which should be considered adequately for eligible research modeling generation are perfect profile, good mesh quality and reasonable boundary conditions. In this paper, the research model is a pair of three-dimensional spur gear, and the mesh quality around the gear tooth surface has been optimized to obtain the most accurate situation of the contact region.

The finite element model of the research modeling can be generated by CAE software tool. For the analysis, it is not necessary to undertake the complete model because there are only few pairs of gear teeth will mesh during defined research duration, so the complete model has been simplified to reduce unnecessary time waste in actual analysis.

For example, the basic parameters of the gear have been listed in Table 1. The simplified finite element model generated according to the presented procedure is shown in Figure 4.

Table 1: Gear Information and Parameters

Type Spur gear

Module 2

Number of teeth 24

Pressure angle 20°

Thickness 10 (mm)

Material Steel

DensityYoung’s modulus

Poisson’s ratio

7.8 (g/cm3) 210000 (MPa)

0.3

Figure 4: Finite element model

Gear design is a highly complicated art and it should be considered lots of questions. The constant pressure to build less expensive, quieter running, lighter weight, and more powerful machinery has

resulted in a steady change in gear designs. Just for one direction of the whole gear design, Teeth Contact Analyses, the designer should notice the contact stress; bending stress, contact noise, vibration, transmission error, and material character, thermal, impact and so on. So the gears design is a refined and complicated job, at present much is known about gear load-carrying capacity, and many complicated processes for making gears are available. Consequently, it is necessary to build a reliable model to simulate gear rating process which can consider geometry and boundary conditions nonlinear behavior in gear tooth contact analysis.

Based on this finite element model, the gear performance analysis results such as bending stress, contact pressure, frictional shearing stress, transmission error and so on can be analyzed significantly. Figure 5 indicates the line chart result which describes the variation situation of gear tooth bending stress. The conclusions regarding the contact phase, bending stress variation, transient response and so on can be summarized for precise understanding for gear rating situation.

Figure 5: Bending stress

4. Computer Simulation on Dynamic Drivetrain Calculation

The noise, vibration and harshness of gearbox are difficult to be regulated effectively due to complicated excitation sources. Too serious unexpected vibration implies the unreliability or uncertain latent failure of gearbox and need to be solved. Actually, the designer should pay attention to the vibration energy and noise level during design process; it is possible to control harmful vibration by optimizing the structure and couplings of gearbox system. For wind turbine gearbox, it is required to carry out dynamic drivetrain calculation for gearbox and submit relevant reports to GL for design certification, and GL also proposed acceptable dynamic drivetrain calculation procedure through computer simulations by professional software tools.

The professional software tools for dynamic drivetrain calculation such as ADAMS and SIMPACK can analyze natural frequency, damping and vibration shape for completed gearbox structure by

Figure 3: Gear geometryCAD model


modal calculation initially, and then carry out frequency domain analysis and time domain analysis base on modal information subsequently to search latent resonance points. The analytical modeling for simulation on gearbox drivetrain can be constructed by the software base on linear and nonlinear dynamic theory. The couplings, flexible parts and bearings should be considered and reflect their particular performance by reasonable simulation in the software. Figure 6 illustrates the dynamic drive-train modeling for a certain type of wind turbine gearbox which is built by SIMPACK software.

According to the requirement of GL design certification, the dynamic drive-train calculation should include following contents:

² The methodology of modeling — to describe the general situation of gearbox drive-train, which includes model topology, mass and inertia data, flexible blade and input load signal, hub model with the information of stiffiness, coupling and bearing parameters, generator simplified model and so on. The reliable simulation modeling is the important base of the total dynamic drive-train calculation.

² Modal calculation — to analyze modal information which includes natural frequency, damping, vibration shape and so on. The modal calculation result indicates the connatural vibrate character, and will be referred for further calculations.

² Frequency domain analysis — to carry out dynamic equilibrium analysis to analyze modal energy distribution and draw 2D Cambell diagram. The results will be used to determine the interference between excitation frequency and natural frequency, and then screen out probable latent resonance points for the first round.

² Time domain analysis — to build time domain frequency sweep model and define time domain simulation duration and sampled frequency in order to generate 3D Cambell diagram with additional time axis. The particular performance parameters such as velocity, displacement and acceleration responses can be illustrated clearly by 3D Cambell diagram, and the probable latent resonance points can be screened out for the second round with the reference of 3D Cambell diagram.

Figure 6: Dynamic drivetrain calculation modeling

² FFT transformation for responses diagram — to ensure the latent resonance points by necessary FFT transformation for the responses diagram of velocity, displacement and acceleration, and consults with the previous probable latent resonance points selection results.

5. Conclusion

This paper has introduced typical application of computer technology in the form of software tools, and proposed particular design procedure with the auxiliary function of computer simulation on wind turbine gearbox design. The reliable gearbox products should be involved in many kinds of professional computer software tools during design process. It is very significant to apply the software which combines with advanced theories and specifications to improve the performance and reliability of gearbox products. For wind turbine gearbox, the mentioned software applications and relevant functions in this paper are really important for design of the project. The gearbox system simulation will determine general situation regarding integrated gearbox design basically; the gear rating simulation will make the designers understand the situation of gear transmission system further; and the dynamic drivetrain simulation and calculation can optimize the design on the basis of dynamic performance of products. In summary, the computer technology has been applied widely and deeply on wind power industry, the quality and accuracy of software tools applied is decisive for wind turbine gearbox design.

Acknowledgment

Many thanks to Dr. Ken Mao, the professor of Department of Mechanical Engineering, the University of Warwick, UK. His technology support on software and necessary consultation are very important for the research.

References

1. H. Hertz, “On the contact of solid elastic bodies and on hardness”, Journal of Math, Vol.92, pp.156-171, 1881.

2. A. Andersson and L. Vedmar, “A dynamic model to determine vibrations in involute helical gears”, Journal of Sound and Vibration, Volume 260 Issue 2, pp. 195-212, 2003.

3. D. W. Dudley, “Handbook of Practical Gear Design”, CRC Press LLC: 1983, p.2.4, p2.7-2.9

4. J. E. Shigley, “Mechanical Engineering Design (First Metric Edition) ”, 1986: p. 467-518, p. 527-539.

5. ABAQUS/CAE User’s Manual Version 6.11, www.ABAQUS.com

6. L. Zheng, “Spur Gear Teeth Contact Analysis on Power-train Transmission Noise, Vibration and Harshness”, Phd dissertation, The University of Warwick, 2010.

7. R. B. Heywood, “Designing by photo-elasticity”, 1st edn. London: Chapman and Hall Ltd.,1952.

8. E. E. Bisson, and W. J. Anderson, “Advanced bearing technology”, 1964, NASA SP-38, pp 150–153

9. R. W. Cornell, “Compliance and stress sensitivity of spur gear teeth”, ASME J. Mech. Des., 103 pp.447–459, 1981.

10. The Help Documentation of SIMPACK Software, version 9.2


Introduction

A gearbox is typically used in a wind turbine to increase rotational speed from a low-speed rotor to a higher speed electrical generator. A commonly ratio is ranging from 20:1 to 90:1. Some multi-mega watt wind turbines have dispensed with a gearbox. In these so-called direct-drive machines, the generator rotor turns at the same speed as the turbine rotor. This requires a large and expensive generator. Other wind turbines on the market sit in-between, with gearbox ratios of about 30:1, dispensing with the highest speed stage in a typical gearbox. There is a trade-off between the reliability of gearboxes and gear stages and the cost of slower, higher torque generators.

The design of a wind turbine gearbox is challenging due to the loading and environmental conditions in which the gearbox must operate. Torque from the rotor generates power, but the turbine rotor also applies large moments and forces to the wind-turbine drivetrain. It is important to ensure that the drivetrain effectively isolates the gearbox, or to ensure that the gearbox is designed to support these loads, otherwise internal gearbox components can become severely misaligned. This can lead to stress concentrations and failures.

Wind-turbine drivetrains undergo severe transient loading during start-ups, shut-downs, emergency stops, and during grid connections. Load cases that result in torque reversals may be particularly damaging to bearings, as rollers may be skidding during the sudden relocation of the loaded zone. Seals and lubrication systems must work reliably over a wide temperature variation to prevent the ingress of dirt and moisture, and perform effectively at all rotational speeds in the gearbox.

Failure Modes of Wind Mill GearboxesTop Failure Modes for Bearings

Abrasion

² Two-body: embedded particles or asperities on one bearing surface abrade the opposing surface

² Three-body: abrasion due to loose contaminants

² Abrasion scratches or gouges on bearing surfaces are in the direction of sliding. Under magnification, scratches appear as parallel furrow that are smooth and clean

² Usually caused by contamination of lubricant by hard, sharp-edged particles. Common contaminations are sand, rust, machining chips, grinding dust, weld splatter, and wear debris.

Adhesion

² Severe adhesion or scuffing is transfer of material from one bearing surface to another due to welding and tearing

² Damage typically occurs in areas of slip in narrow or broad bands along the direction of sliding. It may occur in localized patches with load concentrations

² Scuffing areas appear to have a rough or matte texture, which under magnification, appears to be torn or plastically deformed.

Fretting Corrosion

² Fretting corrosion is deterioration of contacting gear tooth surfaces caused by minute vibratory motion.

² It occurs between contacting surfaces that are pressed together and subject to cyclic, relative motion of extremely small amplitude. Under these conditions, lubricant is inadequate to replenish, permitting metal-to-metal contact and causing adhesion of surface asperities.

² Fretting corrosion damages gear teeth by forming ruts along lines of contact.

Top Failure Modes for Gears

² It consists of three distinctive stages like crack initiation, propagation and fracture.

² During stage 1 no gross yielding of the gear teeth occurs. However, local plastic formation may occur in regions of stress concentrations or areas of discontinuities. The

Wind Mill Gearbox Failure Modes and Repairing – Service with Accuracy

Mr. P. Kanakaraj, Managing Director, M/s. Kay Arr Engineering Services, Kannampalayam, Sulur, Coimbatore [email protected], kayarrengineering.com


end of this stage is symbolized by the formation of micro cracks inside grains.

Top Failure Modes for Gears

² Stage 2 begins when the crack turns and grows across grain boundaries (transgranular) in a direction approximately perpendicular to the maximum tensile stress. Plastic deformation is confined to a small zone at the leading edge of the crack. As a result, the cracked surfaces usually appear smooth without signs of gross plastic deformation.

² Sudden fracture occurs during stage 3. It may be ductile, brittle or mixed-mode depending upon material toughness and magnitude of applied stress.

² High-cycle bending fatigue occurs when cyclic stress is less than the yield strength of the material and the number of cycles to failure is greater than 10,000.

Repair Strategies for Wind Turbine Gearboxes

² There is no single reason why gearboxes fail prematurely, and that is often the most confounding aspect of such failures. An experienced and independent, remanufacturing supplier can look at the various failures by model and provide upgrades to mitigate these failures. As a gearbox-repair supplier, we believe that a gearbox failure in fewer than 10 years is premature.

Just a Few Problems

The most common reasons for wind-turbine-gearbox problems include:

² An extremely low service factor, close to 1 in most cases

² Site conditions, such as capacity factor, wind class, curtailment and others

² Drivetrain chassis is not a rigid foundation which causes system misalignments and a changing gear mesh

² Load sharing of planets, and IMS (Intermediate Speed Shaft) assembly timing

² Dirty or waste-contaminated lubrication

² 320 weight oil is not ideal for high-speed bearings. That weight is a compromise because it is sharing a common sump with the low-speed-planetary section

² Transient loads lead to sudden accelerations and load-zone reversals

² HSS and IMS bearings experience white etch and axial-crack phenomena

² HSS, IMS, Sun and Planets are more susceptible to material related failures due to low safety factors. These are also know as rating elements, the weakest links, so to speak

² Improper bearing settings cause uneven load sharing and high edge stresses

² Softer thru-hardened ring gear is susceptible to debris denting

² Grinding temper

Repair it or Remanufacture it?

² When selecting a remanufactured gearbox supplier, critically review each step of the repair and remanufacturing process. Some suppliers often cut corners, leading to disastrous results in a short period after re-entering service. Repair and remanufacturing are not the same. Repair means that failed component is the only thing addressed. Remanufacturing requires reviewing the entire system and the contents within.

² One example is the use of a four row, cylindrical bearing with a through hardened race in the planet gears. This is not the optimal bearing configuration for the application. When remanufacturing a gearbox of this design, it is highly advantageous to use a case carburized inner race bearing with coated rollers. In addition, altering clearance across the individual rows will optimize the load sharing, thereby allowing for a longer performing bearing. This can also prevent common case-crack failures due to debris that collects in the bottom of the gearbox from a wearing planet bearing. In addition to this specific planet-bearing upgrade, it is also necessary to use case carburized and coated bearings in the high speed and intermediate positions. These simple upgrades can greatly enhance the overall performance of the gearbox, leading to significant life extension.

Up Tower Repairs

² There is significant focus in the field regarding up tower repairs to wind turbine gearboxes. There is certainly a time and place for performing up tower repairs. However, great care must be taken to ensure there is no future reduction in gearbox life as a result of the up tower work. Generally, the most common type of up tower repair replaces the HSS (High Speed Shaft) and IMS (Intermediate Speed Shaft) bearings. It is possible with today’s technology to effectively and correctly replace these bearings. That said, we should take time to develop the scope of work to ensure apples-to-apples comparison across the different service providers.


² Up tower gearing replacement is more difficult and has higher probability of future problems than a simple bearing replacement. It is vitally important to assess the overall health of the planet section prior to performing an up tower repair. If the planet section shows any wear at all, it is time to remanufacture of the gearbox down tower. The planetary section in a wind-turbine gearbox, more specifically the planet bearings, is the rating element. Ultimately a failed planetary section will be the end of the gearbox. If the planet bearings are already wearing, and debris and dirt is introduced to the gearbox during an up tower repair, the planet bearings may fail much more rapidly.

Load Testing

² Another consideration, load testing, cannot happen when a gearbox is in a turbine. One of the premier providers of up tower repairs installs its condition monitoring equipment after its crews perform an up tower repair to monitor the gearbox and ensure it is operating properly.

² When this is not an option, we recommend taking an oil sample upon recommissioning, running the turbine at reduced power for a few weeks, and taking another sample to look for anomalies. It’s important that whoever is performing this work has the correct tools and training, and that case-carburized bearings with coated rollers are used to maximize the performance of the gearbox after the repair is complete.

² Load testing a gearbox after it is remanufactured to full load should be an absolute requirement. Several reasons for performing a full load test include reinsuring that the remanufactured gearbox was assembled correctly, and wearing in gear components while filtering out particulates that may be present as a result of the manufacturing process. Even though wind quality gearing is some of the highest quality produced today, there are surface asperities present that must be filtered out. The basic process of performing a full load test runs the gearbox to various load stages while using alive particle counter on the lubrication system and filtering the lubricant to a specific cleanliness level. Once the correct particle levels are reached, the test can move to the next load stage.

² Another critical process that takes place on the test stand checks for accurate gear meshes. This is done by first coloring gear teeth with a dye and inspecting the wear pattern after a period.

² However, only the high speed gear set in a wind turbine gearbox is visible, so vibration analysis must be used to check all gear meshes, including the visible and non-visible gearing. Because gear profiles are used to optimize load sharing across the entire operating duty cycle, it is essential to take these vibration measurements to peak power to ensure the mesh is accurate.

Service Facilities needed at Engineering Services

The workshop or engineering service provider should have the state of art facilities to undertake wind mill gearboxes servicing and remanufacturing.

Modern equipments are to be used in order to avoid the damages for both casing and internals while dismantling (or) Assy such as Hydraulic press, Hydraulic pullers and shrink fit facilities.

Arial View of Shop Floor at Kay Arr Engineering Services

Kay Arr has modern and precision CNC Operated machines used to manufacture and replace the defective internals like gears, pinions and shafts. Its infrastructure includes inspection of precision and accuracy of gears and profiles.

All profiles of gear and pinion must be ground by latest and hi-tech gear grinding machine. Each and every gearbox should get rebirth like a brand new one by all means like its performance and its aesthetic appearance after its service. All of its performances should be ensured by conducting trial run with no load condition.

Gearbox Trial Run after ServicingTesting of the Gears after Gear Cutting Process

Geared fora Better Future

NGC TRANSMISSION INDIA PVT. LTD.DG Square, Unit 6A, 127 Pallavaram - Thorajpakkam 200 feet Radial Road, Kilkattalai, Chennai 600117Tel: (65) 6589 8588Fax: (65) 6588 3557Email: [email protected]

NGCTRANSMISSION ASIA PACIFIC PTE LTD51 Changi Business Park Central 2, #06-08, The Signature, Singapore 486066Tel: (65) 6589 8588 Ext. 152 Fax: (65) 6588 3557E-mail: APRegion@NGCTransmission

www.NGCtransmission.com/en

NGC is a global leader in wind gearbox development and production with high performance product which can provide complete main gearboxes, yaw and pitch drive product for wind turbine. NGC high reliability product is adapted to various working conditions, low temperature, low wind speed, high altitude, offshore and so on. So far, more than 40,000 NGC gearboxes have been running well all over the world, contributing to continuous power for green energy.

Professional in Wind Gearbox and Transmission System Solutions

Visit us at Booth Hall B5. 434


Snippets on Wind Power

MNRE to Set Up 1000 MW Wind Power Projects

MNRE is planning to set up 1000 MW grid connected wind power projects to benefit utilities in meeting their non-solar RPO norms. The scheme is a positive for wind energy sector as it would encourage the capacity addition in the sector & would enable distribution utilities in states with limited wind potential to honor their non-solar renewable purchase obligation to some extent.

Draft National Wind-Solar Hybrid Policy

India has set an ambitious target of reaching 175 GW of installed capacity from RE sources including 100 GW from solar and 60 GW from wind by the year 2022. Solar and winds are almost complementary to each other and hybridization of two technologies would help in minimizing the variability apart from optimally utilizing the infrastructure including land and transmission system. A draft National Wind-Solar Hybrid Policy has been prepared and has been placed on the website of the Ministry for comments/suggestions.

Rajasthan Curtailing Intake of Wind Power

Wind developers in Rajasthan have been facing losses for the last two months because the state Discoms have been arbitrarily curtailing their intake of wind power, at times two or times a day. These breakdowns by the state load dispatch centers (SLDC) have cost the developers around Rs 100-150 crores in the months of April and May.

Meeting with Ministry of Commerce for boosting Exports & Reducing Import

The Ministry of Commerce called for a meeting on 2nd June 2016 to boost the exports and reduce imports. The meeting was attended by Mr. D. V. Giri, Mr. O.P. Taneja, Mr. Mahesh Vipradas and Mr. Anant Naik from Suzlon and Mr. K. R. Nair from Wind World. A memorandum was also given to the Ministry of Commerce by IWTMA.

IWTMA Installing Devices which will reveal how much Wind Power is Available every 15 Minutes

The Indian Wind Turbine Manufacturers Association is installing devices across 20 substations in Rajasthan, which will reveal how much wind power is available every 15 minutes, making the task of state load dispatch centres (SLDCs) easier. The association is putting up availability-based tariff (ABT) meters and remote terminal units

(RTUs) at these substations. "The Rajasthan Discom Power Procurement Centre wants availability at 15-minute intervals so that they can manage various sources of power with SLDCs," said DV Giri, Secretary General of the Association. ABT meters will provide information on generation such as voltage, frequency and other parameters needed for billing, while RTUs will transmit the information to the system integrator, which will send the data to SLDCs.

Source: Economic Times, May 11, 2016

India's New Wind Project Guidelines give Developers more Responsibilities

MNRE has sought comments on its new Draft guidelines for wind project development that include capacity factor and certification requirements, and some new tasks for the developer. As per the draft the project developer should ensure that grid connectivity is technically and commercially feasible at the chosen site and equipments can be transported to the site using existing infrastructure and “in case any addition is required the same would be created without any legal issues”.

Niti Aayog to Promote India as Renewable Energy Hub

Niti Aayog, the premier think tank of the Indian government, has been assigned the task of promoting India as a renewable energy investment destination, while also developing a strategy so that its target of achieving nearly fourfold output (from 45 GW to 175 GW) can be achieved by 2022. The advisory group at Niti Ayog will oversee the integration of RE into electricity grid by promoting coordination between the Centre and states and suggest interventions required to promote India as an RE investment destination/hub to achieve national renewable energy targets.

World Wind Industry News

The Largest Wind Turbine in the World

LM Wind Power and Adwen of Denmark are jointly developing the largest wind turbine AD 8-180 of 8 MW capacity in the world. It has blade measures a staggering 88.4 meters with a rotor diameter of 180 meters. This monolithic turbine will not only be the largest wind turbine in the world, but also one of the largest mechanical structures on Earth.

Compiled By: Mr. Abhijit Kulkarni Business Unit Head - Energy Segment SKF India Ltd, Pune and IWTMA Team


Photo FeatureGlobal Wind Day and Announcement of "WINDERGY INDIA 2017"

IWTMA Participation in Green Power 2016

Confederation of Indian Industry, Sohrabji Godrej Green Business

Centre conducted International Conference cum Exposition

on Renewable Energy - Green Power 2016 on 30th June &

1st July 2016 at ITC Grand Chola, Chennai. On 1st July a session

on “Opportunities and Challenges in Policy and Regulation of

Wind Energy Sector’ was conducted. The panellists photograph

taken after the session.

From left to right: Mr Amar Variawa, Director-Public Affairs,

Vestas; Dr. R. Kumarvel, AVP, Regen; Mr. Mahesh Vipradas,

Head-Regulatory Affairs, Suzlon; Mr. Sarvesh Kumar, Chairman,

IWTMA & Deputy Managing Director, RRB (Session Chairman);

Mr. Ravi Chander, CII Godrej GBC and Mr. Hemkant Limaye,

Commercial Director, LM Wind Power

Ms. Varsha Joshi unveiled the WINDERGY INDIA 2017 International Conference and Exhibition Brochure after the IWTMA Chairman announced the event. On the occasion, from left to right: Mr. Deepak Gupta, Shakti Sustainable Energy Foundation; Mr. V. Subramanian, Chairman and CEO, InWEA; Ms. Varsha Joshi, Joint Secretary, MNRE; Dr. Pramod Deo, Former Chairman, CERC and Chairman of ‘Wind Discussion Forum’; Mr. Sarvesh Kumar, Chairman and Mr. Chintan Shah, Vice Chairman and Hon. Secretary, IWTMA.

On the occasion of the Global Wind Day on June 15, 2016, Indian Wind Turbine Manufacturers Association (IWTMA), Shakti Sustainable Energy Foundation and the Indian Wind Energy Association (InWEA), conducted a ‘Wind Discussion Forum’ at India Habitat Center, New Delhi. The Forum is an initiative supported by Shakti Sustainable Energy Foundation with technical inputs from Idam Infrastructure Advisory Pvt. Ltd., and guided by an Advisory Group consisting of industry representatives, sector experts and former electricity regulators. It is an independent forum to discuss policy and regulatory issues facing the wind sector and evolve potential solutions through dialogue, and research.

‘Wind Vision 2032’, covering the sector evolution, current landscape, critical issues that need attention, and proposes reaching 200 GW of wind capacity by 2032, was unveiled by Ms. Varsha Joshi, Joint Secretary, Ministry of New and Renewable Energy. The book aims at providing industry’s perspective for the proposed National Wind Energy Mission.

Dr. Pramod Deo, Former Chairman, Central Electricity Regulatory Commission (CERC), chaired the meeting.


Printed by R.R. Bharath and published by Dr. Rishi Muni Dwivedi on behalf of Indian Wind Turbine Manufacturers Association and printed at Ace Data Prinexcel Private Limited, 3/304 F, (SF No. 676/4B), Kulathur Road, Off NH 47 Bye Pass Road, Neelambur, Coimbatore 641062 and published at Indian Wind Turbine Manufacturers Association, Fourth Floor, Samson Towers, No. 403 L, Pantheon Road, Egmore, Chennai 600 008.

Editor: Dr. Rishi Muni Dwivedi

Know Your Member

Suzlon Group pioneered the 'Concept to Commissioning'

model in the wind energy industry, opening the market to

new customer segments. Mr. Tulsi Tanti spearheaded the

wind revolution in India with the founding of Suzlon Energy in

1995. Instituting a new business model, he conceptualized the

end-to-end solution to create realistic avenues for businesses

to 'Go Green' and thus emerged as a strategic partner in

developing sustainable businesses. The Group believes in

connecting its core capabilities to provide optimum renewable

energy solutions. Suzlon is a market leader in India with a

global footprint across Asia, Australia, Europe, Africa, North and

South America. Over the past two decades, Suzlon has built

and consolidated its presence in 19 countries. Suzlon’s global

wind installations help in reducing over 20.50 million tons of

CO2 emissions every year. The Group has 15 manufacturing

facilities spread across India and China (Joint Venture). Having

a dynamic workforce of over 7,500 employees, Suzlon is proud

to support a culture in which employees are respected and

empowered as the company’s most valued assets.

Apart from being a technology leader, Suzlon endeavors

to protect the environment, strengthen communities and

propel responsible growth – a paradigm of Corporate Social

Responsibility. The Group has long been driven by the concept

of sustainable development, its wind turbines with a total

installed capacity of approximately 15.5 GW spread across six

continents, standing as sentinels of a pollution free environment

we can bequeath to the next generation.

The Suzlon Group’s cutting edge technology enables it to offer

an extensive range of robust and reliable products which have

been developed to best suit every requirement. Suzlon’s S97

120m model from its reliable 2.1MW suite of products is the

world’s tallest all-steel hybrid tower wind turbine with a hub

height of 120m above ground level and has been designed to

harness wind energy across low wind sites. Similarly, the S111,

belonging to the reliable and proven 2.1 MW family, has been

designed to ensure highest safety while offering lowest lifecycle

cost that helps drive down the cost of energy for customers. It

features a rotor diameter of 111.8 meters with a swept area of

more than 9,500 square meters, making it one of the highest

yielding wind turbines in its class.

Suzlon is a market leader in India with 100+ wind farms with

an installed capacity of 9.50 GW spread across 9 states. Suzlon

is credited with developing few of Asia’s largest operational

onshore wind farms in Gujarat Rajasthan, Maharashtra, and

Tamil Nadu. The Kutch (Gujarat) and Jaisalmer (Rajasthan)

wind farm of Suzlon till date have a cumulative installation of

over 1,100MW each. Suzlon's diverse client portfolio includes

companies from a variety of industries, including private and

public sector companies, power utilities and independent

power producers.

Suzlon’s Headquarters, One Earth, located in Pune bears

testimony to the Group’s focus on environment sustainability.

One Earth is LEED (Leadership in Energy and Environment

Design) certified and one of the greenest corporate campuses

in the world with Platinum LEED Certification. With wind under

its wings and a number of revolutionary, cutting-edge products

in the pipeline, it is indeed powering a greener tomorrow, today.

AC

E D

ATA

, Coi

mba

tore

Registered with REGISTRAR OF NEWSPAPERS for India, New DelhiVide No. TNENG/2015/60605 Date of Publishing : 18.07.2016

June - July 2016

conference: 11 and 12 january 2017, exhibition: 10, 11 and ... · parthasarathy n, head, driveline...

Documents