A Pulse Width Modulation (PWM) controller is typical in most DC application. this type controller electronically switches on and off at very high speeds to control power output.

Most controllers will monitor overcurrent and overheating conditions, shutting down temporarily if needed. There are also safety interlocks to make sure everything is hooked up right, and some controllers will even monitor other aspects of the motor. 

It is a solid-state device that uses a pulse width modulator (PWM) that sends short bursts of current to the motor. It pulses at a rate of 15 kHz. The speed controller is crucial to the efficiency and smooth operation of a DC Motor.