ELECTRONICALLY COMMUTATED MOTOR (ECM):
(Venkatesan K R, Underwriters Laboratories) The ECM (Electronically Commutated Motor) is a high efficiency programmable brushless (no commutator and brush) DC motor utilizing a permanent magnet rotor (loss approximately zero) and a built- in inverter. Brushed DC motor is having lower efficiency and susceptibility of the commutator assembly to mechanical wear and consequent need for servicing. ECM motors can directly replace the existing Brushed DC motors and fractional horsepower induction motors of the Permanent split / capacitor-start, Shaded pole construction, used in direct drive fans, HAVC (Heating, Ventilating, and Air Conditioning) systems and Refrigerators. Many applications employ the use of an SCR (silicon-controlled rectifier) speed controller on a single or 3-speed motors and this is not the most efficient technology, as they are fundamentally fixed-speed and also due to acoustical considerations, the fan motor is usually adjusted to operate at considerably less than full load (where PSC motor efficiencies may be as high as 62 %) PSC motor efficiency drops off dramatically when turned down, typically by at least half. Installed PSC motor efficiencies are therefore typically in the range of only 12-45%. ECM motors in contrast, maintain a high efficiency of 65-72% at all speeds. Unlike a brushed DC motor, the commutation of a ECM or BLDC (Brushless DC Motor) motor is controlled electronically and to rotate the BLDC motor, the stator windings should be energized in a sequence. It is important to know the rotor position in order to understand which winding will be energized following the energizing sequence. Rotor position may be sensed using Hall effect sensors embedded into the stator. No of Hall effect sensors may vary based on the construction requirements. Most of the BLDC motors have three Hall sensors embedded into the stator on the non-driving end of the motor, based on the hall sensors the controller will...
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