On that board he found a variable resistor combined with a capacitor which control a triac, actuating the speed of a drill. [Ben’s] solution works great and isolates the drill from the control ...

However, if there is a need to achieve lower output speeds with this same motor, engineers would have to control the incoming line frequency since the number of poles of a typical AC motor is constant ...

These motors are often used for fans and can be varied in speed with TRIAC controls ... as the output method to control an AC motor. SCR Drive DC motor drive that uses SCR (Silicon Controlled ...