A servo drive is an electronic device that is part of a closed loop system, producing current and voltage to rotate a servo motor. The closed loop system includes the servo drive, servo motor and feedback device, and is commanded from an analog or digital signal.
Servo drives are available in various voltage and current ratings and may provide position, velocity, and/or torque control. A wide range of servo motor types are controlled using servo drives, including AC, DC , brushed, brushless, rotary, or linear motors. The feedback device can be a potentiometer, Hall effects, tachometer, resolver, encoder, linear transducer, or any other sensor as appropriate. The servo drive powers the motor and compares the feedback data and command reference to verify that the servo motor is operating as commanded. The command signal is supplied from a variety of sources, most commonly from a PLC, CNC, or motion controller.