The AC universal motor drive controls the rotation speed by means of phase-angle partialization. This method consists of changing the RMS voltage applied to the motor. In this case, the voltage is a function of the firing angle of the Triac.
The high commutation capability of ACST family device switches enables a fast change in the firing angle. The conduction angle (α), or firing angle, varies theoretically from 0° to 180°.
ST offers a broad selection of products addressing all aspects of these kinds of applications, helping you reach your goals of high-reliability robustness.