Electronically Commutated Motors
 


Electric motors are one of the major classes of electrical machines that consume the most electricity in industry. There is a continuous effort to reduce the energy consumption of motors in industrial applications, heating, ventilation, and air-conditioning (HVAC) applications for industry and buildings, household, and automotive applications. Advances in motor technology have been driven by a need to reduce power consumption, and also to reduce the weight of electric motors. In HVAC applications, the heat emitted from the motor is a factor that influences the total energy consumption of the device. These technology drivers have paved the way for the development of electronically commutated motors (ECM), which have advantages over alternate current (AC) motors and other direct current conventional motors. Commutation is the application of current to motor phases for production of optimum motor torque. Electronically commutated motors consume only as much as half of the power consumed by conventional AC motors. Some of the latest electronically commutated motors are about 80% efficient, compared to the 45% efficiency of certain AC motors.

Electronically commutated motors are differentiated from other motors in that they are usually brushless DC motors. In brush-type motors, commutation is done with a commutator and graphite brushes. In an electronically commutated brushless motor, it is done with electronic commutation achieved with a microprocessor. Commutation is achieved by switching electronics, which can obtain information on the position of the rotor by means of sensors (e.g., Hall effect types). ECMs have been proven in numerous applications. ECMs are efficient at part load due to efficient speed control. The manufacturing costs of ECMs tend to be more than that for conventional AC induction motors. However, the lifecycle cost savings can make up for these additional costs. ECMs have a longer life due to the lower running temperatures when compared to AC motors and other DC motors. They also have longer bearing life due to the possibility of "soft-start" (for example, limiting the inrush current at initial start-up).

A new class of electronically commutated brushless motor, the flux-switching (FS) motor is gradually emerging in power tools and household appliances. This motor offers advantages of both high-power density and relatively high efficiency. Flux switching motor technology developed at the University of Leicester in England has been commercialized by means Technelec Ltd. based in Oakham, UK. The brushless motor technology of Technelec Ltd. has a rotor, which has no windings. The stator of the motor contains the excitation coils. Therefore, this motor is suitable for high speed. The flux switching motor offered by the company is a brushless motor technology, which functions on a low-cost sensorless electronic controller. The motor technology has been developed for several automotive and domestic applications. The simplified design of the motors enable easy manufacturing.

Several automotive companies, such as Delphi Saginaw Steering Systems based in Saginaw, Michigan, USA, and TRW Automotive based in Livonia, Michigan, USA, have formed collaborations with universities for the development of technology related to brushless permanent magnet and ECMs.

Details:

Charles Pollock

Technelec Ltd

Edison House

Station Approach

Oakham

LE15 6QW UK.

Phone: +44-0-1572-771-199

E-mail: charles.pollock@technelec.co.uk

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