Variable fan speed controllers
Electronic fan speed controllers provide infinitely variable speed control for single-phase or three-phase voltage controllable motors. Typically they are used to control AC fans or pumps in HVAC applications. They use phase angle control - TRIAC technology - to adjust the motor voltage and to control the fan speed. Thanks to this technology, these fan speed controllers are completely silent. Depending on the motor type, some additional motor noise at low speed might occur.