REPORT OF INDUSTRIAL SUMMER TRAININGPRODUCTION AND QUALITY CONTROL OF A.C. MOTORSThis consists of the training report, an outcome of summer training done by me at Marathon Electric, Faridabad. As the title suggests this report is about the production A.C. motors and describing all the assembly and passing line processes of motor manufacturing plant.

2009

RAHUL SINGH RANAECHELON INSTITUTE OF TECHNOLOGY, FARIDABAD

INDUSTRIAL SUMMER TRAINING REPORT

ON

PRODUCTION AND QUALITY CONTROL OF A.C. MOTORS

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DETAILS

DOCUMENT: “INDUSTRIAL SUMMER TRAINING REPORT” forthe Partial fulfillment of award of Degree of Bachelors of Technology in Applied Electronics and instrumentation by M.D.U, Rohtak.

COMPANY: Marathon Electric India Private Limited EXPORT DIVISION Sector-11. Model Town, Faridabad- 121006 (Haryana) India

TYPE OF WORK: Manufacturers and exporters of AC motors. Training Obtained in Quality Control department under the

guidance of Ms. Ruchi Gautam (SR. In charge- Quality Control Department) and Mr. Sachin Gupta (Dy. Manager Manufacturing).

SUBMITTEDBY: RAHUL SINGH RANA,

07-AEI-31, 5th semester

SUBMITTED TO: Echelon Institute of Technology, Training and Placement Cell, Faridabad

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ACKNOWLEDGEMENT

This project report has been possible through the direct and indirect Cooperation and in-valuable assistance of various officers bears the Imprint of their efforts for my work.

I extend my grateful thanks to Mr. Sanjeev Sharma (G.M. –Marathon Electric India Pvt. Ltd. EXPORT DIVISION) and Mr. S.K. Yadav (Factory Manager), for letting me work under their extremely talented staff & giving me a chance to bring out best in myself for the benefit of the Industry.

I wish to express my sincere thanks and appreciation to all those under whom I took my training and interacted especially to Ms. Ruchi Gautam (SR. In charge- Quality Control Department) and Mr. Sachin Gupta (Dy. Manager- Manufacturing) their thoughts and invaluable guidance helped me in broadening my understanding and knowledge of working in an organization.

I also thank to the staff member of, Marathon Electric India Pvt. Ltd., Faridabad in Production & Quality control department for their help and support & allowing me to acquaint myself with the overall congenial atmosphere, which Exists in the organization.

Finally, I owe my thanks to all the faculty members of Echelon Institute of Technology, Faridabad who helped and guided me in making of my training report.

Rahul Singh Rana(07-AEI-31)

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COMPANY PROFILE

Marathon Electric is part of the Regal Beloit family of companies. Regal Beloit Corporation is a leading manufacturer of electrical and mechanical motion control and power generation products serving markets throughout the world. Regal Beloit is headquartered in Beloit, Wisconsin, and has manufacturing, sales, and service facilities throughout North America and in Mexico, Europe and Asia. A leading international manufacturer of electrical and mechanical motion control components headquartered in Beloit, Wisconsin. From electric motors and generators to gear reducers, and electronic switchgear, Regal Beloit's products are often concealed within, but essential to the function of much of the equipment powering the world. You will find Regal Beloit products in home furnaces, pumps, elevators, conveyors, x-ray machines, office equipment, power stations and thousands of other critical uses.

Regal Beloit's strength is in its market diversity as it serves an expansive array of markets from heavy industry to high technology. Markets include Heating Ventilating and Air Conditioning (HVAC), food processing, medical, material handling, petro-chemical, construction, manufacturing, agriculture and mining, to name a few. Few companies can match Regal Beloit's abilities to adapt and modify products to required specifications and deliver consistent quality, at a fair price and a time dictated by the customer.

Regal Beloit's ongoing success can be attributed, in part, to an aggressive acquisition program, which has become a company hallmark. 2004 saw two major motor acquisitions from General Electric (GE), which effectively doubled the size of Regal Beloit. In 2007, the Company acquired Morrill Motors, a leading manufacturer of fractional horsepower motors for commercial refrigeration and freezer markets. With the acquisition of Fasco and Jakel that same year, Regal Beloit expanded into blower systems for the HVAC market. Alstom’s motor and fan business in India was then purchased, another step in the execution of the Company’s globalization

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initiative. The Company now has over 17,000 employees and 54 manufacturing and service/distribution facilities throughout the United States and in Canada, Mexico, Europe, Asia and Australia.

Since 1913, Marathon Electric’s name has been recognized for engineering excellence, custom-designed products and an extensive product line of industrial quality motors. Available in all popular enclosures from 1/12 HP through 800 HP and in a variety of mounting configurations, Marathon Electric’s unique designs provide more ways in which to add accessories, such as blowers, brakes and encoders, to motors than anyone else in the motor business. State-of-the-art lab facilities are equipped and staffed with the finest resources available to ensure successful utilization of products. Since 1913, Marathon Electric has been dedicated to providing customers with quality products for targeted applications. Located in Wausau, Wisconsin, the company is composed of two strategic product lines: motors and generators.

Marathon Electric Motors delivers efficient mechanical power solutions using AC electric motors up to 1250 HP.

Marathon Electric Generators offers power generation for the 21st century with a wide selection of generators (5 to 3,000 kW) for stand-by and continuous power. Proven top performers in every respect, Marathon Electric Generators offer powerful performance, reliable power generation, and easy installation.

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TABLE OF CONTENTS

S.NO. CONTENT NAME PAGE NO.

01. DOCUMENT DETAILS 0302. TRAINING CERTIFICATE 0403. ACKNOWLEDGEMENT 0504. COMPANY PROFILE 06-0705. TABLE OF CONTENTS 0806. 1- ELECTRIC MOTORS 0907. 1.1- PRINCIPLE OF OPERATION 0908. 1.2- A.C. MOTORS 1009. 1.2.1- TYPES 1010. 1.2.2- HISTORY 1011. 1.3- INDUCTION MOTOR 1112. PROCESS LAYOUT 1313. 1.3.2- CONSTRUCTION 1414. 1.3.2.1- STATOR 14-1515. PASSING LINE 1616. 1.3.2.2- ROTOR 2617. ASSEMBLY LINE 2918. MAIN COMPONENTS 3619. MOTOR PARTS 3720. BIBLIOGRAPHY 38

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1. ELECTRIC MOTORS

An Electric motor is a machine which converts electric energy into mechanical energy.

1.1 PRINCIPLE OF OPERATIONCurrent carrying conductor placed in a magnetic field, experiences a mechanical force whose direction is given by Fleming’s Left-hand rule and whose magnitude is given by F = BIl Newton.

(Figure 1: ELECTRIC MOTOR FAMILY TREE)

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1.2 AC motor

INTRODUCTION

An AC motor is an electric motor that is driven by an alternating current. It consists of two basic parts, an outside stationary stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the rotating field.

1.2.1 Types of AC motor (depending on the type of rotor used):

1. Synchronous motor: This rotates exactly at the supply frequency or a sub multiple of the supply frequency. The magnetic field on the rotor is either generated by current delivered through slip rings or by a permanent magnet.

2. Induction motor: This turns slightly slower than the supply frequency. The magnetic field on the rotor of this motor is created by an induced current.

1.2.2 HISTORY

In 1882, Serbian inventor Nicola Tesla identified the rotating magnetic induction field principle and pioneered the use of this rotating and inducting electromagnetic field force to generate torque in rotating machines. He exploited this principle in the design of a poly-phase induction motor in 1883. In 1885, Galileo Ferraris independently researched the concept. In 1888, Ferraris published his research in a paper to the Royal Academy of Sciences in Turin.

Introduction of Tesla's motor from 1888 onwards initiated what is sometimes referred to as the Second Industrial Revolution, making possible both the efficient generation and long distance distribution of electrical energy using the alternating current transmission system, also of Tesla's invention (1888). Before widespread use of Tesla's principle of poly-phase induction for rotating machines, all motors operated by continually passing a conductor through a stationary magnetic field (as in homo-polar motor).

Initially Tesla suggested that the commutators from a machine could be removed and the device could operate on a rotary field of electromagnetic force. Professor Poeschel, his teacher, stated that would be akin to building a

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Perpetual motion machine. This was because Tesla's teacher had only understood one half of Tesla's ideas. Professor Poeschel had realized that the induced rotating Magnetic field would start the rotor of the motor spinning, but he did not see that the counter electromotive force generated would gradually bring the machine to a stop. Tesla later obtained U.S. Patent 0,416,194, Electric Motor (December 1889), which resembles the motor seen in many of Tesla's photos. This classic alternating current electro-magnetic motor was an induction motor.

Michail Osipovich Dolivo-Dobrovolsky later invented a three-phase "cage-rotor" in 1890. This type of motor is now used for the vast majority of commercial applications.

1.3 INDUCTION MOTORS

Most AC motors are induction motors. Induction motors are favored due to their ruggedness and simplicity. In fact, 90% of industrial motors are induction motors.

Induction motors are the workhorses of industry and motors up to about 500 kW (670 hp) in output are produced in highly standardized frame sizes, making them nearly completely interchangeable between manufacturers (although European and North American standard dimensions are different). Very large induction motors are capable of tens of megawatts of output, for pipeline compressors, wind-tunnel drives, and overland conveyor systems.

1.3.1 PRINCIPLE OF OPERATION

Based on rotating magnetic induction field principle, the rotating and inducting electromagnetic field force generates torque in rotating machines. Conversion of electrical power into mechanical power takes place in the rotating part of the motor. In Induction motors rotor receive electric power by induction in exactly the same way as the secondary of a 2-winding transformer receives its power from the primary. That is why such motors are known induction motors.

One means of creating a rotating magnetic field is to rotate a permanent magnet as shown in (Figure 2 (below-next page)).If the moving magnetic lines of flux cut a conductive disk, it will follow the motion of the magnet.

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The lines of flux cutting the conductor will induce a voltage, and consequent current flow, in the conductive disk. This current flow creates an electromagnet whose polarity opposes the motion of the permanent magnet– Lenz's Law. The polarity of the electromagnet is such that it pulls against the permanent magnet. The disk follows with a little less speed than the permanent magnet.

(Figure 2: Rotating magnetic field produces torque in conductive disk.)

Nicola Tesla conceived the basic principles of the poly-phase induction motor in 1883, and had a half horsepower (400 watts) model by 1888. Tesla sold the manufacturing rights to George Westinghouse for $65,000.Most large (> 1 hp or 1 kW) industrial motors are poly-phase induction motors. By poly-phase, we mean that the stator contains multiple distinct windings per motor pole, driven by corresponding time shifted sine waves. In practice, this is two or three phases. Large industrial motors are mostly 3-phase motors.

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1.3.2 CONSTRUCTION

An Induction motor consists essentially of two main parts:

1. A stator and 2. A rotorBoth are assembled together as one assembly, rotor known as an armature, a stator containing windings connected to a poly-phase energy source as shown in (Figure 3- below):

(Figure 3: TESLA POLY-PHASE INDUCTION MOTOR)

1.3.2.1 Stator

It is made up of a number of stampings, which are slotted to receive the windings. It is wound for a definite number of poles, (the no. of poles P, produced in the rotating field is P = 2n where n is the no. of stator slots/pole/phase) the exact no. of poles being determined by the requirements of speed. Greater the no. of poles, lesser the speed and vice versa.

(Figure 4: Addition of field poles decreases speed)

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A 2-pole (pair of N-S poles) alternator will generate a 60 Hz sine wave when rotated at 3600 rpm (revolutions per minute). The 3600 rpm corresponds to 60 revolutions per second. A similar 2-pole permanent magnet induction motor will also rotate at 3600 rpm. A lower speed motor may be constructed by adding more pole pairs. A 4-pole motor would rotate at 1800 rpm, a 12-pole motor at 600 rpm. The style of construction shown (Figure 4 (above)) is for illustration. Higher efficiency higher torque multi-pole stator induction motors actually have multiple poles in the rotor. For a 3-phase induction motor, stator windings when supplied with 3-phase currents, produce a magnetic flux, which is of constant magnitude but revolves (or rotates) at synchronous speed (given by Ns = 120f/p). This revolving magnetic flux induces an e.m.f in the rotor by mutual induction.

The stator in (Figure 3) is wound with pairs of coils corresponding to the phases of electrical energy available. The 2-phase induction motor stator above has 2-pairs of coils, one pair for each of the two phases of AC. The individual coils of a pair are connected in series and correspond to the opposite poles of an electromagnet. That is, one coil corresponds to a N-pole, the other to a S-pole until the phase of AC changes polarity. The other pair of coils is oriented 90o in space to the first pair. This pair of coils is connected to AC shifted in time by 90o in the case of a 2-phase motor. In Tesla's time, the source of the two phases of AC was a 2-phase alternator. The stator in (Figure 3) has salient, obvious protruding poles, as used on Tesla's early induction motor. This design is used to this day for sub-fractional horsepower motors (<50 watts). However, for larger motors less torque pulsation and higher efficiency results if the coils are embedded into slots cut into the stator laminations. (Figure 5)

(Figure 5: Stator frame showing slots for windings.)

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The stator laminations are thin insulated rings with slots punched from sheets of electrical grade steel. A stack of these is secured by end screws, which may also hold the end housings.

Generally a wound stator is called as a field (or stator field) in terms of production, the plant or place where whole process of insulation and insertion of winding and other processes takes place is called as passing line i.e. where fields are produced. Following processes are carried out at passing line :

1. INSULATION

Insulation paper which is a good quality mica sheet is inserted into the slots of the stator at slot insulator machines.

Stator core is built from high-quality low-loss silicon steel laminations and flash-enameled on both sides.

Insulation paper is inserted into the slots accordingly as the stack height, slot width, shape and dimensions, generally stack heights varies from 18mm to 500mm. A wide range of insulating machines is available in the market.

(Figure 6: INSULATING MACHINE)(Courtesy: Statomat Machines)

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General check points for insulation are proper checking for stack height, diameter and other mechanical dimensions of stator core, besides insertion of slot paper should be uniform and of equal height with no shifting down from its original position.

2. WINDINGThe coils are wound on an external fixture, and then worked into the slots. Insulation wedged between the coil periphery and the slot protects against abrasion.

ndings.)

(Figure 7: Stator with (a) 2-φ and (b) 3-φ windings.)

In (Figure 7 (above)), the windings for both a two-phase motor and a three-phase motor have been installed in the stator slots. The coils are wound on an external fixture, and then worked into the slots. Insulation wedged between the coil periphery and the slot protects against abrasion. Actual stator windings are more complex than the single windings per pole in (Figure 7 (above)). Comparing the 2-φ motor to Tesla's 2-φ motor with salient poles, the number of coils is the same. In actual large motors, a pole winding, is divided into identical coils inserted into many smaller slots than above. This group is called a phase belt. See (Figure 8 (below- next page)).

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The distributed coils of the phase belt cancel some of the odd harmonics, producing a more sinusoidal magnetic field distribution across the pole. The slots at the edge of the pole may have fewer turns than the other slots. Edge slots may contain windings from two phases. That is, the phase belts overlap.

(Figure 8: Winding structure.)

A brief description of various types of windings along with the machines used is given below:

Concentric Winding

There are many features like the automatic stack height adjustment and the graphical user interface based on MS Windows. The A-Winder (model of winding machine) is available in a single spindle and a dual spindle version:

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(Figure 9: A2 Single Spindle Winder)

Wave Winding

It’s a distributed or non-distributed coil (also known as split phase and non-split phase winding). The waves are formed directly during the winding process which saves space and guarantees an optimal winding result.

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(Figure 10: Types of Wave Windings)

Loose-Tooth / Bobbin Winding

As the demand for higher slot-fill-factors reaches the limits of conventional winding/inserting technologies, more and more motor makers start wind directly on the single stator teeth that are assembled afterwards or bobbins that are assembled into segmented stators. To ensure a maximum fill-factor, the wires are exactly positioned to prevent the problem of twisted wires.

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(Figure 11: Winding machine-SWK 1/2)(Courtesy: Statomat Machines)

3. INSERTION

Wound coils are inserted into the stator slots at insertion machines along with the wedge paper for insulation of coil periphery from stator laminations and adjoining coils. A great care is taken for proper insertion of wedge paper into the slots.

4. FORMING

The best winding and insertion still doesn't make the perfect stator, Forming process is another focal point in the production process. Processes carried at this stage are such as expanding lamellas, to final forming of I.D., O.D. and heights of the winding head, scratch wire detection. After this lead or cables connection are made to the field

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Winding and insulation tapes are applied according to the specifications as per E.I. chart.

(Figure 12: Forming press-ZFM-K)(Courtesy: Statomat Special Machines India pvt. ltd.)

The ZFM-K is a very economical press for smaller stator. The stator is loaded manually directly into the tooling. The ZFM-K opens the stator bore and as an option pushes back the wedges and performs the winding head.

5. LACING

Lacing or knotting is done at the machine for finally tightening the all the loose wires of coil winding. The end turns are laced with a "diamond" stitch pattern. Both sides are laced at the same time and a real knot is being tied at the end. After this process the wound stator looks like in

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figure and then the final process is carried out on field where final inspection is done for visually detecting and removing the defects on account of following:

Loose wires/wiring, Lacing or knotting problem. Wedge paper problem, shifted down wedge paper. Slot paper. Cables or connecting lead length and proper application of

insulation tape. Without marking.

This is the most critical and important stage of passing line from point of view of quality control. At this stage the responsibility lies wholly on operator as there is no intervention of machinery and the defects have to be detected visually and removed manually.

6. COMPUTERIZED WINDING TEST

DESCRIPTION

Computerized winding tester is the most comprehensive quality control method for in-plant testing process industries. It is extremely effective as a diagnostic tool to evaluate and detect any windings fault that may exist.

It can be used to detect the following in the windings: turn – to – turn short circuits coil – to – coil short circuits phase – to – phase short circuits reverse coil connections open coils grounded coils defective insulation

The following tests are performed by the computerized winding tester:

Resistance test: The Resistance test is performed on the Main and Auxiliary windings. All the resistance measurements are corrected to the ambient temperature (25° C) using the temperature sensors. It checks wrong turn count, poor connections, mislabelled leads, and incorrect wire size.

Insulation resistance test: The IR or megohm test checks the strength of the insulation.

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AC Hi-Pot test: The AC hi-pot test detects if there is a breakdown to ground or between windings which would otherwise go undetected using average current measurement techniques. This measures the resistive portion of the leakage current, rather than the total current.

Surge test: The high voltage surge test checks for insulation problems between turns, coils, and phases of the winding. Surge tests can also detect other faults which change the inductance of a winding such as reversed coils. The surge test also has the ability to detect corona caused by weak insulation in addition to actual insulation breakdown.

Rotation test: The rotation direction test determines the rotation of the stator whether it is clockwise or anti-clockwise. This test uses the Hall-effect type sensors.

To manufacturers this means that the faulty windings can be isolated and repaired at every stage of manufacturing thus, ensuring quality and saving in material and labour costs.

(Figure 13: Manual Surge Comparison tester)(Courtesy: Ample Machines)

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(Figure 14: Computerized Winding test machine)(Courtesy:The Automation Engg. Inc. , Fort Wayne, Indiana)

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7. VARNISHING

Finally the Wound stator i.e. the field after being properly checked goes for varnish plant where penetrating coat of good insulating varnishes are applied on windings to protect them from action of vibration, heat, water, oil, dirt and acid fume would soon cause a complete failure of field or rotor circuits. Without a coating of insulating varnish, slot papers would soon become brittle and crack or soggy from moisture and the enamel covering of wires would chip and flake. When properly applied and treated, insulating varnish provides a solid film protective covering. At varnish plant there are two stations Loading (here fields are loaded for varnish process on to the hangers) and Unloading station (fields are unloaded from the hangers), the whole process takes almost about 4 to 5 hours. At both loading and unloading stations thorough inspection of fields is done to detect visually for: Loose wires or wiring in green fields (at loading station) Wedge paper problem. Loose wires or wiring in varnished fields (at unloading station) Without marking. Knotting/lacing problem. Lead cut/unequal length/terminal damage.

From the point of view of quality control the inspection made at varnish stations for defect is most crucial, since the varnished fields are passed on for assembly line and if rejection is made on basis of above problems during any stage of assembly line results in wastage of resources, manpower and time.

1.3.2.2 Rotor

The rotor consists of a shaft, a steel laminated rotor, and an embedded Copper or aluminium squirrel cage, As compared to a DC motor armature, there is no commutator. This eliminates the brushes, arcing, sparking, graphite dust, brush adjustment and replacement, and re-machining of the commutator. They are of two types as follows:

1. Squirrel-cage Rotor: Almost 90% of induction motors employ this type of rotors because of simple and rugged construction and almost indestructible. The rotor consists of a cylindrical laminated core with parallel slots for carrying the rotor conductors, which are not wires but consists of heavy copper bars.One bar is placed in each slot; rather the bars are inserted from the end where semi-closed slots are used. The rotor bars are brazed or electrically welded or bolted to two heavy and stout short-circuiting end-rings.

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(Figure 15: Laminated rotor with (a) embedded squirrel cage, (b) conductive cage removed from rotor)

The squirrel cage conductors may be skewed, twisted, with respect to the shaft. The misalignment with the stator slots reduces torque pulsations.

2. Phase-wound Rotor: Motors employing this type of rotors are called ‘wound’ motors or as ‘Slip-ring’ motors. This type of rotor is provided with 3-phase, double –layer, distributed winding consisting of coil as used in alternators. The rotor is wound for as many poles as the no. of stator poles and is always wound 3-phase even when the stator is wound two-phase.

Rotor Stack laminations are die casted to form a rotor stack in which shaft along with end rings is inserted in to this by process of Drop-on, and then this shaft-rotor assembly is allowed to cool. After this process this shaft-rotor assembly is passed on for Rotor test:

1. ROTOR TEST

DESCRIPTION

Rotor Test System is designed to evaluate the Electromagnetic properties of squirrel cage rotors. The test system consists of Mechanical and Display unit, interconnected by cable. The test set operates on the basis of inductive measurement, it accept a wide range of rotors, from small type to pump rotors which have long shaft. It can be operated with minimum efforts.HOW THE EQUIPMENT WORKS?

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The test set operates on the basis of electrical & magnetic effects caused by the circulation of induced currents into the winding of a rotor, which is made to turn at a constant speed, with in a magnetic field produced by a permanent magnet.

The induced magnetic field produced by permanent magnet, acts on one slot at a time. However, the direction of magnetic fields is such that the turns of a moving coil cut the lines of force normally. The induced currents, which are proportional to the field intensity distance of magnet from the rotor, on the speed of rotation (constant) & on the rotor characteristics, produce magnetic fields, the symmetry of which enable a clear observation of the turns in the short-circuited condition.

A fixed probe subjected to the magnetic fields produced by the rotor under test, provides the signals, which after being amplified, are applied to picture tube.

The induced e.m.f cause voltages to appear between the commutator laminations & the amplitude, shape & recurrence of these voltages permits the location of faults in the rotor winding.

APPLICATIONS Broken or interrupted rotor bars. Poor or missing connections to the rotor end rings. Rotor bar resistance measurement. A short circuit between two or more bars. Error in the relative position between commutator & slots. Non-uniformity between lamination of the commutator. Deviation of the skew angle.

After this, shaft-rotor assembly is passed on to for I.D. (Internal Diameter) Reaming and O.D. (Outer diameter) Reaming, which is done with help of Micrometer. This is again a very important stage from point of view of Quality Control, since the responsibility lies wholly on operator.

The next step is that of lacquering and painting the shaft-rotor assembly, this is done manually by applying a good quality resin based lacquer which is done with help of brush, the lacquer used for the purpose is generally oil mixed shellac based compound, which forms a thin and a highly elastic insulation layer on the rotor surface.

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(Figure 16: Rotor Tester machine)

After all above mentioned processes shaft-rotor assembly, stator (Field winding) from passing line along with miscellaneous parts such as follows:

Nuts Clamp Bolts Gourmet(Conduit Adapter) Shell

Is brought to the assembly line which is the final stage of production, the major processes carried here are as follows:

1. Shell Field Pressing: Here the shell is pressed on to the field, i.e. the stator is inserted into the shell. After this the Conduit Adapter (Gourmet) is inserted into the punched hole made in the shell along with insertion of elfy which is a special adhesive used to hold gourmet in the place tightly.

2. Assembly of Motor: Here the Rotor-shaft Assembly is inserted into the Stator-shell assembly, along with the end shield casing; the bolts are inserted always in diagonally opposite manner, the connecting leads are taken out from Conduit adapter.

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3. Running of Motor: Here the Motor is tested by running it on the input supply voltage and current which is a little higher than that specified by customer requirements.

4. Noise Testing: This is a most important stage of assembly line from point of view of Quality control, basically it is a Inspection Stage where all assembled motors are tested for Noise limit, the whole arrangement is enclosed inside the sound proof glass walls, with two operators employed on the noise testing Machine.

The Noise, Resonance & Vibration Test System runs on the Windows™ operating system as well as user-friendly software package. It has built-in signal conditioning, an A/D converter for sensor measurements, relays for digital I/O control and powerful application software for noise, resonance and vibration testing. It is intended for use on AC and DC motors directly on the production floor.

Tests Performed:

Noise: Noise testing analyzes audible noise, generated by a motor, by doing a frequency analysis and comparing it to an envelope based on a median of setup motors. The analysis must have a certain percentage of data points fall within this envelope or the part will fail. There are six different ranges available for noise - 1000 Hz, 2000 Hz, 3000Hz, 5000 Hz, 7000 Hz and 10,000.

Vibration & Resonance: Resonance testing analyzes a combination of audible noise and vibration, generated by a motor, by doing a frequency analysis and comparing it to an envelope based on a median of setup motors. This method tests for resonance by making contact with the motor body and determines at which frequency and amplitude the motor is resonant. The resonant frequency is much larger than other frequencies generated within the motor. Resonance is processed the same as noise and uses the same ambient noise cancellation feature as for noise. Resonance is measured in Rones. There are four ranges available for Resonance - 500 Hz, 1000 Hz, 2000 Hz and 3000 Hz.

Ambient Cancellation Technique : Cancellation testing technique identifies the ambient noise, resonance and vibration levels on the factory floor and then separates them from the noises, resonance's and vibrations created by the motor-under-test.

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This is done each time a motor is tested, allowing for ambient sampling on every motor.

Collection Methods:

Resonance Acoustic Probe :

The vibration data is collected using an “Exclusive” Resonance Acoustic Probe. This unique probe breaks up air movements and ambient noises into white noise. The sound channels used are specifically designed for the motor-under-test. A combination of highly repeatable transducers and Noise Cancellation Software eliminates 90% - 95% of ambient factory noise and vibrations.The Resonance Acoustic Probe converts mechanical movement from the motor and motor casing into sounds. The diaphragm controls the movement of air (the vibration) down the chamber into the collection device. The tester is then able to look at the frequencies generated by the movement of the motor before these noises and vibrations are dispersed into the air. This probe eliminates the contamination of other frequencies that could have been picked up along the way. Only the true readings are displayed.The Resonance Acoustic Probe is equipped with spring-loaded constant pressure transducer. This transducer was developed exclusively for noise & vibration analysis and is highly repeatable. Special emphasis is placed on the location of these transducers. The transducer’s position is isolated from the holder (transducer) and the motor test fixture to ensure that the vibration picked up is from the motor.

Microphone:

The use of microphones (even high-end products costing thousands of dollars) will not guarantee getting “good” broadband frequency data. In fact, higher-end microphones also pick up movements and ambient conditions, resulting in poorer data.

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(Figure 17: Noise Testing System)

Some of common problems/faults encountered from quality point of view if a digital noise testing system is not used:

Opinions vary shift to shift as well as person to person. All Operators have their own opinions of a good versus bad parts. Factory noise levels from 60-85dB. No data is available on defects and or returns. Process and Statistical control is not available. Many operators have several tasks in addition to listening to the parts.

5. NLT (No Load Test): This is an Inspection stage of Production Control, at this stage various tests are performed on assembled motor out of which No Load is most important one both from production and quality point of view, a short description of all the tests are given as below:

No-Load Test (AC or DC): Performed for Voltage, Current, Power, Power Factor, Speed (RPM) & Direction.The No Load test is performed by unloading the shaft of the motor as much as possible or applying it as close to zero torque as possible. A

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regulated AC voltage is applied to the motor leads and motor voltage, current, wattage and direction are monitored. A low voltage start test will also be done prior to these no-load tests.Three types of no load tests can be provided: disconnected, inferred no-load and measured no-load.

Load Point Test (AC or DC):

Performed for Voltage, Current, Electrical Power, Power Factor Speed (RPM), Direction, Torque, Mechanical Power and Efficiency.As many different load steps as needed can be programmed for a given motor-under-test, or a continuous speed vs. torque curve can be generated.

To measure a specific Load Point, the dynamometer is set to control in either speed mode or torque mode, depending on customer preference. If the dynamometer is controlling speed (speed mode testing), then a speed is established by the dynamometer and torque is produced based on the capabilities of the motor. If the dynamometer is controlling torque (torque mode testing), then a load is established by the dynamometer and speed is produced based on the capabilities of the motor. In either case, once the desired point is established, the tester can measure speed, torque, voltage and current (amps) depending on how the individual tester is configured.

The most commonly used single load point is the full load point. This means that the speed selected is the motor’s rated speed (if speed mode testing is used) or the load selected is the motor’s rated torque (if torque mode testing is used). Then any data gathered is full load data. As many load points as desired can be gathered.

Locked Rotor (AC):

Performed for Voltage, Current, Electrical Power, Power Factor, Torque, Direction.Another common load point is known as “Locked Rotor” or “Stalled Torque”. A full current is applied to a Hysteresis Brake, Dynamometer, or by simply clamping or “locking” the motor shaft and energizing the motor. More torque is produced by the Dynamometer/Brake than the motor can produce. In this state the shaft cannot turn, simulating the rotor being “locked” or “blocked”.

This test is very hard on a motor. There is a large amount of current that flows into the rotor, causing it to heat up rapidly. As a result, this test must be performed very quickly. A motor, with a locked rotor, draws up to six or seven times its rated current (sometimes more). The power supply used

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must be capable of regulating the motor voltage adequately during rapid changes in current to ensure the proper voltage is maintained when the data is being taken.

Locked rotor torque testing is important. If the motor cannot produce enough torque to overcome the friction in the load, as it sits without rotating, the motor can be energized but it will not start the load. If the motor remains in this state for very long it will overheat and fail.

This criteria indicates whether or not a motor may be more likely to suffer from nuisance tripping during motor starts and determines whether the motor exceed the National Electrical Manufactures Associate (NEMA) locked-rotor current limit. This performance measurement can help indicate the reliability of the motor.

Standard Features:

Fast Model Changeover Shaft Rotation Detection DC Resistance Testing at 100mA to 1 Am 50 / 60 Hz Temperature Compensated DC Resistances    to 25°C AC Hipot Testing Industrial Computer With Backup Hard Drive CDR/W Intel Processor Windows 2000 or XP Nine-Lead Connections for 5-Speed Motors   with Start Winding or

Three Phase   Dual Voltage Motors High Current DC Resistance Testing 10 Amps to 50 Amps for 0.1 micro

OHM Resolutions DC Hipot High Current Hipot 100mA, 1 Amp High Voltage Hipot up to 10KV 12-Lead Connections Thermal Overload Continuity Testing

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(Figure 18: NLT Testing Station)(Courtesy:The Automation Engg. Inc. , Fort Wayne, Indiana)

After this stage the assembled motor is passed through firewall test, from where it is passed on to for final packaging, where name plated is placed on the motor casing, and it is packed after oiling the shaft, so as to prevent it from rusting in a palette of 175 motors each.

6. SCAT: This is an inspection stage of quality control; here six motors are randomly selected from a palette of 175 motors and selected tests are performed on motor which are same as that done at NLT and Noise testing. Motors which do not pass this test are sent back to concern point of production line where the failure took place.

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Main Components

End ShieldShell

Rotor Shaft AssemblyField

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MOTOR PARTS

BIBLIOGRAPHY

1. “Textbook of Electrical technology- Volume 2” – B.L. THAREJA, A.K. THAREJA

2. “Electric Machines” – J.B. Gupta

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3. www.marathonelectric.com4. www.autoeng.com5. Wikipedia, Google

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