Variable Frequency Drives (VFD) for AC Motors

AC Variable Frequency Drives (also known as VFD, or Inverter) control the speed of an AC Induction motor by varying both the voltage and frequency to the motor. They only work with 3-phase motors, not single-phase motors. However, there are VFDs that accept single-phase input and convert to 3-phase for the motor, such as the Weg CFW100 line. VFD drives coupled with AC motors are quickly replacing DC drives and DC motors as the preferred method of varying the speed of an electric motor due to the much lower cost and maintenance of the AC motors.