Electronically commutated motor

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An electronically commutated motor (ECM) is a brushless motor which relies on the external power drive to perform the commutation of stationary copper winding on the stator. This changing stator field causes the permanent magnet rotor to rotate.

A brushless permanent magnet motor is the highest performing motor in terms of torque / vs. weight or efficiency. Brushless motors are usually the most expensive type of motor. Electronically commutated, brush-less DC motor systems are widely used as drives for blowers and fans used in electronics, telecommunications and industrial equipment applications.

There is wide variety of different brush-less motors for various applications. Some are designed to to rotate at constant speed (those used in disk drives) and the speed of some can be controlled by varying the voltage applied to them (usually the motors used in fans). Some brushless DC motors have a built-in tachometer which gives out pulses as the motor rotates (this applies to both disk drive motors and some computer fans). In general, users select brush-type DC motors when low system cost is a priority, and brushless motors to fulfill other requirements (such as maintenance-free operation, high speeds, and explosive environments where sparking could be hazardous). Brushless DC motors are commonly used in applications like DC powered fans and disk drive rotation motors.