Variable speed motor controllers regulate the speed and/or torque of asynchronous motors. Depending on the application, there are controllers from a few hundred Watts up to several hundred Kilowatts.

Figure 1. The chart shows energy savings achieved by Refrigeration Service Co. with use of a variable-speed controller. EDITOR’S NOTE: This material was prepared by Heatcraft Worldwide Refrigeration.

En route to getting the off-the-peg DC-51 motor speed controller to better suit my small milling machine, I had a go at working out what the circuit is. Approx circuit of DC-51 motor speed controller ...

Model VSM-CA3 modulates the speed of motors in fancoil units, fan-powered VAV terminal units, fan filter units, and other air-moving devices. The controller provides modulating control of AC induction ...