Brushless motors
Brushless DC electric motor (BLDC motors, BL motors) also known as electronically commutated motors (ECMs, EC motors), or synchronous DC motors, are synchronous motors powered by DC electricity via an inverter or switching power supply which produces an AC electric current to drive each phase of the motor via a closed loop controller. The controller provides pulses of current to the motor windings that control the speed and torque of the motor.
The structural element of a brushless motor system is typically a permanent magnet synchronous motor, but can also be a switched reluctance motor, or an induction motor.
Brushless motors may be implemented as stepper motors as well; however, the term "stepper motor" tends to be used for motors with a radically different design and is controlled with an open loop (hence the controller cannot detect when the stepper does not step due to too high shaft load; there is no shaft position sensor). They are frequently stopped with the rotor in a defined angular position while still producing torque. A well designed brushless motor system can also be held at zero rpm and finite torque. Two key performance parameters of brushless DC motors are the motor constants KT (torque constant) and Ke (back-EMF constant also known as speed constant KV = 1/Ke ).
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