Universal motors can be used with AC or DC supplies and are commonly used in many kinds of appliances such as mixers, fans and vacuum cleaners.
Most universal motors are unidirectional. Bidirectional motors using two coils on the stator can be driven by applying a voltage to only one of them for the respective direction. The advantages of universal motors are their high starting torque, very compact design and high speed. A simple controller, using an AC supply, can be implemented using a low-end microcontroller and a single Triac or an AC switch. Improved performance can be achieved using a DC chopper drive that rectifies the AC current and uses a power MOSFET to provide a pulse width modulated (PWM) drive to the motor.