Brushless DC Motors

The BLDC motor uses electronic commutation to control the current through the windings. The BLDC motors use permanent magnets on the rotor. The BLDC motor contains rotor position sensor electronics so that the power input wave form to the windings is in sequence with the proper rotor position. Motor efficiency is enhanced because there is no power loss in the brushes. In the BLDC motor, the stator is wound with electromagnetic coils that are connected in a multiphase configuration, which provides the rotating field, and thearmature consists of a soft iron core with permanent magnet poles. Sensing devices define the rotor position. The commutation logic and switching electronics convert the rotor position information to the correct excitation for the stator phases. Sensing devices include hall-effect transducers, absolute encoders, optical encoders, and resolvers. The electronic controller can be separate or packaged with the motor.

Uses:
  • High rpm applications
  • Light weight applications
  • Low thermal emission applications

Advantages
  • High speed (up to about 100000rpm)
  • High torque at high speed
  • Approximately double the output torque of Brush DC motor of the same size
  • Improved heat dissipation over of Brush DC motor as the windings are on the stator.
  • Motor lasts as long as the bearings hold up as there are no brushes to wear out.
  • Higher efficiency
  • Vacuum compatible

Disadvantages
  • Higher electronic cost
  • Greater motor drive complexity

See also: AC Induction Motors, Brush DC Motors, Electric Motors, Stepper Motors.

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Subjects: Electrical Engineering