Q3Advanced Electric Drives

In Current Source Inverter (CSI) based control of a synchronous motor, a controlled current (rather than voltage) is injected into the stator windings from a CSI fed by a DC link inductor that maintains a substantially constant DC current. The synchronous motor's own back-EMF, generated by its rotating field (excited by a separately controlled DC field winding or permanent magnets), naturally commutates the load-commutated inverter's thyristors at speeds above a small starting threshold, eliminating the need for forced commutation circuitry - this load-commutated inverter (LCI) drive configuration is widely used for very large synchronous motor drives, such as large industrial compressor and pump drives, precisely because it exploits the motor's own back-EMF for commutation.