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.
LE15 6QW UK.
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