A motor speed controller is an electronic device that regulates the speed of an electric motor. It adjusts the power supplied to the motor, allowing for precise control over its speed and torque. This is essential in various applications, such as in electric vehicles, industrial machinery, and home appliances. These controllers can operate using different methods, including pulse-width modulation (PWM) and voltage control. By changing the voltage or the duration of power pulses, the controller can effectively manage the motor's performance, enhancing efficiency and extending its lifespan.