Technologies for EnergyEfficient Electric Motors
Sebastião Lauro Nau, Dr. Eng. – slnau@weg.net
Research and Technological Innovation Department - WEG Motores
Rua Venâncio da Silva Porto, 399 - Malote 41
89252-230 - Jaraguá do Sul - SC, Brasil
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Summary
 Introduction
 Switched Reluctance Motors
 Synchronous Reluctance Motors
 Permanent Magnet Motors
 Examples of Industrial Energy-Efficient Motors
 Examples of Energy-Efficient PM Motors for Special
Applications
 Conclusions
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Introduction
 Induction motors:
 widely used due to simplicity, robustness, reliability, direct-on-line
operation.
 Variable-speed drives:
 energy savings in fluid-flow applications, elimination of gear boxes in
low-speed high-torque applications, wide-speed range in variable-speed
applications.
 induction motors with scalar or field-oriented control.
 brushless ac pm motors and synchronous reluctance motors with fieldoriented control (or scalar control for small motors using Hall sensors).
 brushless dc pm motors and switched reluctance motors with
electronic commutator.
 Comparisons are always difficult, depend on application requirements
(speed range, maximum speed, efficiency, noise).
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Reluctance Motors
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Switched Reluctance Motors
 No magnets, no squirrel cage
 No Joule losses in the rotor
 Independent pole windings (no
electrical connection between phases)
 Same power/frame ratio as induction
motors
 Higher vibration and acoustic noise
 Require sophisticated electronic
controller (current control to reduce
vibration and noise problems)
 Applications: where wide speed
range and high speed are necessary
like pumps, household appliances,
electric vehicles, etc.
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Synchronous Reluctance Motors
 No magnets, no squirrel cage
 No Joule losses in the rotor
 Similar stator as induction motors
 Same power/frame ratio as induction
motors
 Require electronic controller (fieldoriented control)
 Higher current, lower power factor
Applications: pumps, elevators,
compressors, conveyor belts,
extruders, etc.
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Permanent Magnet Motors
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Characteristics
 The most efficient of all motors
 High torque-to-current and torque-to-volume ratios
 High power factor
 Require electronic controller
 Use Rare-earth or Ferrite magnets
 BLAC or BLDC type with several rotor configurations
 Applications: pumps, elevators, compressors, blowers, conveyor
belts, extruders, generators, electric vehicles, servodrives,
household appliances, etc.
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
BLAC and BLDC Motors
 PM BLAC (brushless ac) Motors or PMSM (permanent
magnet synchronous motors):
 Similar windings as for induction motors
 AC-sinewave drive with field-oriented control
 Low torque ripple and acoustic noise
 PM BLDC (brushless dc) Motors:
Distributed windings
 Usually have concentrated windings
 DC-squarewave drive for phase commutation
 Generally used in low-power applications
Concentrated windings
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Surface-Magnet Motors
 BLAC or BLDC motors
 Distributed or concentrated windings
 Rare-earth or Ferrite magnets
 Easier rotor manufacturing
Distributed windings
 Poor field-weakening capability (low inductance)
 Usually no reluctance torque
 Concern about retention of magnets against
centrifugal forces in high-speed operation
Concentrated windings
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Interior-Magnet Motors
 BLAC or BLDC motors
 Mostly distributed windings
 Rare-earth or Ferrite magnets
 Improved field-weakening capability
 Higher leakage flux
 Reluctance torque
 More difficult rotor manufacturing than surface PM
motor
V-shape magnets
Tangential magnets
Multi-layer magnets
Radial magnets
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Exterior-Rotor PM Motors
 BLAC or BLDC motors
 Mostly concentrated windings
 Mostly Ferrite magnets
 Surface-magnet rotor
 Higher torque-to-volume ratio than interior-rotor
motors
8-pole pm motor
 No reluctance torque
 Easier rotor manufacturing
 No concern about retention of magnets against
centrifugal forces in high-speed operation
16-pole pm motor
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Electronically Commutated (EC) Motors
 BLAC or BLDC motors
 Higher efficiency than PSC and shaded-pole motors
 Mostly concentrated windings
 Mostly Ferrite magnets
 Surface-magnet rotor
 Low-power applications (residential and commercial
applications)
 No reluctance torque
 Easier rotor manufacturing
 Very low-power motors can have the electronic
controller integrated within the motor enclosure
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Line-Start PM Motors
 Hybrid induction/pm motors
 Similar windings as for induction motors
 Rotor cage for asynchronous starting
 Permanent magnets beneath the cage for
synchronous (steady-state) operation
 Rare-earth magnets
 More difficult rotor manufacturing than surface PM
motor
 Do not need electronic controller for DOL operation
 Limited to low-inertia applications, due to
synchronization capability
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Rare-earth PM challenge
 Since early 2011, prices of NdFeB PMs have been increasing
considerably, due to China’s limited quotas and raised taxes on
rare-earths exports.
 Increasing price of rare-earth magnets poses a possibility of
magnet manufacturing in other countries, including Brazil.
 Prices of Rare-earth magnets are not stabilized yet.
 Search for efficient but non-rare-earth motor technologies
Samarium
Neodymium
Source: http://www.metal-pages.com
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Magnets Consumption at WEG
2010:
Ferrite: 1175 kg
NdFeB: 2366 kg
2011:
Ferrite: 997 kg
NdFeB: 2863 kg
NdFeB Price Increase (average):
Sep11/Jan11: 300%
Nov11/Jan11: 250%
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Examples of Industrial
Energy-Efficient Motors
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
IPM Motor With High-Energy PM (Rare-earth)
 Wmagnet Drive System: since 2009
 Same inverter as for induction motor –
CFW-11 (sensorless control)
 Output: 11kW – 150kW
 Base speed: 1500 and 3000 rpm
 Frames: 132S – 250S/M
 High-energy rare-earth magnets in the
rotor  Super Premium Efficiency
 Higher torque/volume ratio (one frame size
smaller than induction motor)
 Extended life time
 Applications: pumps, elevators,
compressors, conveyor belts, extruders,
centrifuges, etc.
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Line-Start PM Motor With High-Energy PM
(Rare-earth)
 WQuatro: since 2010
 For DOL starting
 Output: 0.37kW – 7.5kW
 4 and 6 poles
 Frames: 80 – 132M/L
 Specially designed aluminum cage
 High-energy rare-earth magnets beneath
the cage  Super Premium Efficiency
 Same power/frame as for induction motor
 Applications: low-inertia loads
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Examples of Energy-Efficient PM
Motors for Special Applications
HVAC applications
Washing machines
Cooling towers
Electric vehicles
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
High-Eff. PM Motors for HVAC Applications
 Example: EC motor for ventilation application
 Surface ferrite magnets
 Integrated drive, 115 or 230V, 60Hz input
 Nema 48 frame, 1/4 to 1HP
 200 – 1750rpm
 80% total efficiency
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
High-Eff. PM Motors for Washing Machine
 PM motor for front-load washing machine
 External rotor, surface ferrite magnets
 Power at agitation: 60W
 Efficiency at agitation speed (400rpm): 66%
 Efficiency at spin (850rpm): 86%
 High torque @ low speeds
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
High-Eff. PM Motors for Washing Machine
 PM motor for top-load washing machine
 Radial ferrite magnets
 Rated power: 1/3HP
 Efficiency at agitation cycle: 66%
 Efficiency at spin cycle: 86%
 High speed
 Low torque
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
High-Eff. PM Motors for Cooling Tower
 High-energy PM magnets
 Direct-drive: eliminates gear-boxes  less
maintenance and less mechanical losses
 High-torque, low-speed motor
 Drive with sensorless control
 Power: 15kW – 150kW
 Torques: 500 – 10000NM
 Speeds: 100 – 300 rpm
 Frames: 355 – 450 (special frames with
shorter axial dimension)
 Extended life time
Example of a 45kW, 200rpm, 2150Nm cooling tower motor.
Efficiency: 94.3%
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
High-Eff. PM Motors for Electric Vehicles
 High-energy PM magnets
 Rated Power: 21kW
 Base speed: 3600rpm
 Maximum speed: 10000rpm
 Water cooled
 Drive input voltage: 220V
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Conclusions
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro
Comparison of Several Motor Technologies
Reference: induction motor
Symbols:
---=
much lower
lower
slightly lower
similar to induction motor
+
++
+++
slightly higher
higher
much higher
I Seminário Brasileiro de Terras Raras - 07/12/2011 - Rio de Janeiro