“pro's & con's of electric motor types” - mining · pdf...
TRANSCRIPT
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 1
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
By: Dr. Keith Klontz and Dr. Howard Li
9 May 2014
Induction
Wound-Field Synchronous
Permanent magnet (AC)
Synchronous Reluctance
Switched Reluctance (w/ Focus on Integral HP AC machines)
“Pro’s & Con’s
of Electric Motor Types”
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 2
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Advanced MotorTech
Design Engineering & Optimization
Drawing Review & Package
Training & Tutorials
Theoretical Analysis
Finite Element Method Analysis
Prototype Manufacturing
Research
Development
Modeling & Simulation
Testing & Data Evaluation
Manufacturing Process
Job Cost Analysis & Cost Reduction
Energy Efficiency Economics
Patent Writing & Review
Product & Technology Comparisons
Re-Design, Upgrades, Modifications
Repair & Re-Building
Failure Analysis
Technical Writing & Publication
Selection & Application
High Efficiency or High Power Density Trades
Design, Purchase or Service Specifications
Prototype Project Management
Component Sourcing
Technology Reviews
Founded in 2005 to provide advanced
electric machine and power magnetics
technology to industry.
Member: SMMA, EASA, IEEE, EMERF Bd of Dir Technical Partner: JSOL Corp.,CD-Adapco
Business Partner: PowerSys
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 3
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Differences: • Phase Number • Rotor Construction • Starting Method • Speeds Built In • Rotor Excitation • Controller Type • Current Shape
Also, Flux Direction: • Radial • Axial • Linear • Tubular • Transverse
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 4
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
PMAC Synchronous
Overview: Similarities and Differences of Electric Motors
• All motors operate by opposing magnetic forces at
the air gap causing motion
• Stator (Stationary) usually gets it magnetic field by
current thru coils;
• 3 phase: smooth flux variation (sinusoidal);
produces rotating magnetic field
• The key difference is in how the Rotor gets its
magnetic field
Switched Reluctance
Induction
Synchronous Reluctance
Wound-Field Synchronous
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 5
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
PMAC Synchronous
Overview: Similarities and Differences of Electric Motors
• How the Rotor gets its magnetic field:
• Permanent magnet motors—special material,
no current
• Synchronous motors—Coils on rotor with dc
• Induction motor—transformer principle,
stator is primary
• Synchronous reluctance—flux from stator
• Switched reluctance—flux from stator, plus
shape effect
Switched Reluctance
Induction
Synchronous Reluctance
Wound-Field Synchronous
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 6
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Overview Similar and Difference of Motors
From: SPEED’s Electric Motors by TJE Miller
• Difference is in how rotor excitation is achieved: influences how motor is started
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 7
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Interior magnet Surface magnet
Many variations
Permanent Magnet (PM) Motor ― Rotor
• Synchronous speed based on
frequency: RPM = 120 *f /Poles
• Magnets are used for excitation
• Line start PM motor needs rotor
current
• Requires controller
• Higher efficiency and power density
than other motors
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 8
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Permanent Magnet Motor: Magnet Material: Enabling Technology
Demagnetization Curves for different types of magnet materials
So
urc
e: S
. T
rou
t/M
ag
neq
uen
ch
1940’s
1950’s
1970’s 1980’s
Histogram for different types of magnet materials
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 9
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com • NdFeB (since about 1980):
– Large BHmax to >48 MGOe
– High Hc and Br (1.1 - 1.2T & 800KA/m)
– Feasible operating temperature 80ºC - 200ºC
– Linear characteristic, -10%/100ºC
– Medium cost
• SmCo:
– Good magnetism characteristics (1.0T & 700KA/m)
– High operating temperature 200ºC - 350ºC
– Expensive
• Ferrite:
– Normal magnetism characteristics (0.42T & 230KA/m)
– Normal operating temperature 200ºC
– Least expensive, lowest cost for unit of torque
• AlNiCo:
– Seldom used in machine
– non-linear BH
– Easy to demagnetization
– Better magnetism characteristics (1.2T & 80kA/m),but low Hc
– Very high operating temperature 600ºC
– Expensive
Permanent Magnet Motor ― Rotor Material
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 10
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Operation of PM Motor
– Windings are located in the stator, and build the stator field in air gap,
looks rotating
– Air gap field: sinusoidal or trapezoidal
– Rotor Excitation: Permanent magnets produce the excitation field in air gap
– Principle: Two magnetic fields interact and develop electromagnetic torque
and rotate with synchronous speed
– Most PM motors require position sensor, speed sensor & controller
PM Motor ―Pros & Cons
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 11
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Pro’s of Permanent Magnet Motors
– Efficiency, Variable Speed, Motion control, High Speed
– Inherently synchronous, needs help to start
– Rotor Excitation: permanent magnets (PM), requires no current, but not
controllable
– Lower rotor weight, Lower total weight, and inertia
– Application: many areas– hybrid vehicle, high accurate control, high
efficiency application
PM Motor ―Pros & Cons
1500hp, 4 pole, line-start PM
motor
Induction cage
Ventilation hole Shaft
Permanent magnet
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 12
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
PM Motor ―Pros & Cons
• Con’s of Permanent Magnet Motors
– Control: Overload causes motor stop, need a controller
– Starting: need controller, or induction cage
– Temperature Sensitivity: Magnets weakens with temperature
– Safety: Magnets never ‘turn off’
– Magnet cost, new manufacture process
– Little control of magnetic field strength
– Brittle material, can crack & chip
Demagnetization due to eddy current and overheat
Broken magnet
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 13
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
PM Motor ―Pros & Cons
• Speed
Runs at synchronous speed. Precise speed adjustment by using controller (frequency)
• Efficiency
PM motor has a higher efficiency than induction motor and wound field synchronous
motor, because magnet loss is much smaller than that of excitation coils.
• Reliability
No rotor conductors to break; cooler rotor extends bearing and insulation life. Robust
construction for years of trouble-free operation; Must have banding for centrifugal forces
• Power density
Rotor physical size is smaller than induction and synchronous motors. Very higher power
density (kW/ kg); Beware: Weight is more proportional to Torque, not Power; P=T*N
• Cost
--RE magnet material is commodity, 95% ore is in China;
--PM motor more expensive than induction motor mostly due to lower volumes,
--High efficiency is good investment; low lifetime operating cost.
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 14
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Wound-Field Synchronous Motor ― Structure
Wound-field Synchronous Motor Two common variants: 1) Round rotor & 2) Salient Pole
Replace magnets with Coils
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 15
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Salient rotor
4 poles
Round rotor
2 poles
north
south
shaft
coils
Rotor
core
Synchronous Motor ― Rotors • Synchronous speed based on frequency
• Salient rotor with damper winding can be
used for synchronous motor to get line-start
• External sources using slip ring or exciter
(generator) provide power supply of rotor,
no induction
• Adjust excitation current to control Rotor
magnetic field strength, hence torque and
output power
Damper winding (bars)
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 16
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com • Operation of Synchronous Motor
– Synchronous speed, but needs help to start
– Rotor Excitation: wound coils, needs power source on rotor, now rotor field is
controllable
– Gap field: usually sinusoidal, big air gap
– Two magnetic fields develop electromagnetic torque, rotate with synchronous
speed (fixed in rotor frame)
– Application: generator, large compressor, high power operation, synchronous
speed, High efficiency
– To start
• Damper bars as cage rotor
• Pony motor to start—Hydro Gen
Synchronous Motors
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 17
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Pro’s of Synchronous Motor
– Generator with Voltage Control
– Controllable Power Factor
– Mature, well-suited for large sizes
– Highest proven efficiency for large sizes >10,000 hp, >10 MW
– High inertia, good ride-through capability
Synchronous Motors
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 18
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Synchronous Motor ―Pros & Cons
• Con’s of Wound-Field Synchronous motor
– Overload causes motor stop and lost synchronization
– Starting problem, very hard to start just by excitation winding
– Need DC power to rotor coils; has losses due to rotor current:
• 1) Slip rings: Regularly maintain brushes, bearing and slip ring
• 2) Exciter = AC Gen with diode rectifier
– Stable operating angle: power angle < 60 degree; need stability control
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 19
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Synchronous Motor ―Pros & Cons • Speed
Frequency of AC power determines the speed of synchronous motor.
--For 60Hz, speed will be 120*60/2p, 2p is pole number of synchronous motor.
--For variable speed job, must have Variable Frequency Drive (VFD)
• Efficiency
Higher efficiency than induction motor. Copper excitation winding of synchronous motor has
a lower loss than induction motor’s aluminum cage. Adjustable power factor will also
improve PF of industrial plant and decrease losses of power system.
• Reliability
Brushes and slip ring or Exciter will be an issue for long time operating. Regular
maintenance service is required. Wider air gaps than induction motors make them
mechanically better. Loss heat from both stator and rotor
• Power density
Higher power density than induction motor because of copper winding used on Rotor
• Cost
The complicated design makes the synchronous motor more expensive than induction motor.
However, above 10 megawatts, the higher efficiency of synchronous motors brings lower
operating cost.
Note: Some are now advocating wound-field synchronous motors for EV/HEV traction motors
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 20
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Induction Motor ― Structure
Stator
winding
Stator iron core
Electrical
port
Mechanical
port Rotor iron
core
Rotor Winding,
cage in this case
Electrical
port
Mechanical
port
Energy
Conversion
process
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 21
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Wound rotor
– Windings embedded in slots, terminals brought to
(3) slip rings and brushes
– Connect resistors to windings’ terminals to adjust
the starting performance or regulate speed
• Cage rotor
– Bars embedded in slots and short circuited at both
ends by end rings
– Special case of wound-rotor design
– Bars and end rings like a squirrel cage
Cage rotor Wound rotor
Induction Motor ― Rotors
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 22
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Properties of induction motor
– Winding build a fundamental rotating magnetic field
– Rotor Excitation: induced current in wound or cage rotor, Slip speed to get
transformer action
– So, “torque producing field” slowly rotates with respect to rotor
– More complicated due to transformer action used to create rotor excitation
– Never achieves synchronous speed
– 1) Wound Field: secondary of transformer
– 2) Cage Rotor: cage is on short circuit and generate short circuit current to build an
excitation field
– Two magnetic fields develop electromagnetic torque, rotate with synchronous speed
(fixed in rotor frame)
– Application: many areas, general drive
Induction Motor ―Pros & Cons
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 23
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Pro’s of induction motor
– One of very few that can Line-Start without special controls
– Air gap field: sinusoidal, shaped by stator field
– Very robust, very durable, ubiquitous
– Rotor magnetic field strength controllable by stator current
– Mature speed & torque control (Vector Control, Field Orientation)
– Application: many areas, general drive
This technology is the benchmark that
others should be compared to:
“Is it better than using an induction motor?”
Induction Motor ―Pros & Cons
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 24
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Con’s of induction motor
– Speed varies with load torque
– Low starting torque
– Low power factor
– Peak torque may not be enough at overload situation
– High starting current, soft-starting may be required
– For wound rotor, regularly maintain brushes and increase cost due to slip ring
and brushes
– Rotor heat due to losses of rotor bar and end ring; meltdown at locked rotor
– Rotor cage reliability: broken bars; limited number of starts in motor lifetime
Induction Motor ―Pros & Cons
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 25
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Speed
Must run different than synchronous speed to develop torque.
• Efficiency
Even NEMA- premium efficiency units exhibit degraded efficiencies at low load with low
power factor. Full load has much better efficiency, but sometimes to avoid starting or
lock rotor issues, engineers always choose a big motor to drive a small load.
• Reliability
More loss heat are from both stator and rotor, and it degrades insulation, motor
operation and life time.
• Power density
Induced field generated by squirrel cage embedded in iron core limits power density.
• Cost
Can start without expense and losses of VFD. The simple design and huge quantities of
manufacture make them less expensive, but higher operation costs (electrical power) –
very good, but not best efficiency for VFD systems
Induction Motor ―Pros & Cons
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 26
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Synchronous Reluctance Motor―Pros & Cons
--Structure
Synchronous reluctance motor
New kid on the block: You will be hearing about this as the newest, greatest motor --It is good, but neither superlative
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 27
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Synchronous Reluctance Motor
Properties of the Synchronous /Reluctance Motor
The stator has a normal lamination and winding
The rotor is designed to maximize the saliency ratio Xd/Xq; iron vs. air
Rotor Excitation is from set of balanced, polyphase AC sinewave currents in Stator
Operates at Synchronous speed
Torque is from alignment of rotor iron with stator magnetic field
Note: varies from Switched Reluctance (SR) by shape of stator iron and shape of
current from power supply, hence stator magnetic field
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 28
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Synchronous Reluctance Motor
Pro’s of the Synchronous /Reluctance Motor
Efficiency and power-factor are comparable to induction motors
Saliency ratio of at least 10 is needed to match induction motors (difficult)
Torque/speed characteristic is inverse; good low speed torque
Torque/current characteristic is non-linear
Good overload capability
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 29
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Synchronous Reluctance Motor
Con’s of the Synchronous Reluctance Motor
Small airgap required
Difficult to design for high speed
--Limited mechanical strength against centrifugal force
--Balance problems
Axially-laminated rotor has potentially high iron loss;
Hard to manufacture rotor
Torque ripple is difficult to eliminate
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 30
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Synchronous Reluctance Motor
• Speed
Runs at synchronous speed. Needs VFD, so speed is variable, but torque is inverse
characteristic. Not well-suited for high speed due to structure
• Efficiency
Can be quite high; comparable to Induction, not quite as good as PM; Good controller
can give good efficiency at partial load; starting torque dependent of controller, typical
150%.
• Reliability
Some loss heat in rotor—lower than Induction, higher than PM; Simple and robust rotor
structure
• Power density
Rotor field generated by stator current, iron rotor core limits power density.
• Cost
Needs VFD. The simple design can make them less expensive, –very good, but not best
efficiency for VFD systems
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 31
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Switched Reluctance Motor ― Pro’s & Con’s
12slot/8 pole SR motor
6slot/4 pole SR motor
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 32
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Switched Reluctance Motor ― Rotor
• Synchronous speed based on 2X frequency
• Rotor material: simple lamination
• Requires complex controller and feedback
sensor
• Simple rotor, no magnet and winding
Slot/pole configuration For 2 phase: 4/2, 8/4, 4/6, 8/12, 12/18, 16/24
For 3 phase: 6/2, 6/4, 6/8, 12/8, 18/12, 24/16
For 4 phase: 8/6, 16/12, 24/18, 32/24, 8/10
For 5 phase: 10/4, 10/6, 10/8, 10/12
For 6 phase: 12/10, 24/20, 12/14
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 33
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
• Properties
– Operates at synchronous speed
– Laminated rotor, torque by alignment of iron parts
– Gap field: square, needs small air gap to get high torque
– Requires specialized controller, virtually none OTS
– Application: some good examples for high power, mostly for home application,
Step-motors, motion control
SR Motor ―Pros & Cons
12slot/8 pole SR motor
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 34
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com • Pro’s of Switched Reluctance
– Synchronous speed, Motion Control
– Simple, Robust rotor; no magnet and no winding –Big attraction feature
– Strengths: medium sizes, robust
– Excellent candidate for very high speed, > 50,000 rpm
– Stator magnetic field pass through rotor steel teeth and develop reluctance
torque between steel
– Only single phase’s switch is on at any time; Can have good fault tolerance
SR Motor ―Pros & Cons
Dyson
Remember: Power = Torque x Speed
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 35
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
SR Motor ―Pros & Cons
• Con’s of Switched Reluctance motor
– Vibration and noise, torque ripple — Serious problem
– More lead wires
– Require a Special controller – Serious problem
– Not many commercial manufactures or OTS controller ; None in high HP
– Very small air gap
90dB
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 36
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
SR Motor ―Pros & Cons
• Speed
Frequency of AC power determines the speed of SR motor. For 60Hz, speed will be
120*60/P, P is pole pair of SR motor. Variable speed with controller
• Efficiency
Most of SR motors have similar efficiency with induction motor when having same speed
and power, but lower power factor
• Reliability
No winding, no magnet in rotor. Simple rotor structure and special operation bring very
high reliability. Phase winding is isolated in electrical circuit each other, good fault isolation
& tolerance.
• Power density
Higher power density than induction motor and lower than PM motor.
• Cost
Very simple design in both stator and rotor make SR motor cheaper in basic material cost,
but low quantities make the price high. Additionally, the SR motor needs a specialized
controller for operation. It is well-suited for variable speed, very high speed application.
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 37
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com
Summary Induction motor Synchronous motor PM motor SyncRel motor SR motor
Rotor and stator
cage rotor or wound rotor
Would-field rotor, round or salient rotor, damper winding
Magnet, surface PM or IPM, damper winding
Laminated rotor, normal winding for stator
Laminated rotor, concentrate winding for stator
Speed Must run less than synchronous speed; varies with load
Synchronous speed, need damper winding for line start
Synchronous speed, need induction cage for line start
Synchronous speed Half speed of synchronous speed
Efficiency Degraded efficiency at low load operation
Higher efficiency than induction motor
High efficiency than induction motor and synchronous motor
Similar efficiency with induction; better at partial load
Similar efficiency with induction or synchronous motors
Reliability More heat degrade insulation and life time, many years of proven performance
Brushes or slip ring are issues for long life operating, regular maintenance in fewer years
Lower temperature reduce maintenance, trouble-free operation for years.
Good reliability due to simple rotor
Higher reliability than others due to very simple rotor
Power density
Induction field & rotor iron limits power density
Higher power density than induction motor
Higher than induction and synchronous motors
Power density similar to induction motor and lower than PM motor
Higher power density than induction motor and lower than PM motor
Cost Simple design and high manufacture quantities lower price, but high operating cost
Higher price than induction, but above 10kW, high efficiency brings low operating cost
Higher cost, but higher efficiency gives low operating cost
Lower material cost , but low quantities. Mfr assembly difficult. Need a VFD controller
Lower material cost , but low quantities. Needs a special controller
Application Many areas, any power, general drive
Many areas, high power, synchronous speed
Many areas, small to high power, high efficiency
Newly available; target is Induction motor applications
Some good examples, mostly for home application; noisy
12 June 2014 ***Confidential*** ©2013 Advanced MotorTech LLC Pinellas Park FL USA ***Confidential*** 38
ADVANCED MOTORTECH LLC
4951 71st Avenue North
Pinellas Park, FL 33781-4428
Phone: 727 - 412 - 8200
Fax: 727 - 412 - 8299
www.AdvancedMotorTech.com