Definition
A servo drive controls a servo motor using a closed feedback loop (typically from an encoder or resolver) so it can hold or follow a commanded position, speed, or torque with high accuracy and fast dynamic response. Where a standard VFD mainly regulates output frequency, a servo drive continuously compares actual motion feedback against the command and corrects the difference in real time.
Key facts
- Operates as a closed loop: actual position, speed, or torque feedback (encoder/resolver) is compared to the command in real time.
- Delivers higher dynamic response and positioning accuracy than a standard VFD, suited to indexing, synchronization, and coordinated axes.
- Commonly paired with a servo motor built for high torque density and low rotor inertia.
- Tuning parameters (gain, acceleration limits) directly affect stability and settling behavior of the controlled motion.
How does Servo drive work or appear?
A servo drive receives a motion command (position, speed, or torque setpoint) from a controller such as a PLC or motion controller, then drives the connected servo motor while continuously reading back actual position or speed from an encoder or resolver. The drive compares the feedback to the command at a high update rate and adjusts output current and voltage to minimize the following error.
What should technicians inspect for Servo drive?
A VFD (variable frequency drive) typically runs open-loop or with basic sensorless estimation and targets speed control for fans, pumps, and conveyors rather than precise positioning. A servo drive's defining feature is closed-loop feedback for tight, dynamic motion control: the distinction that matters for selecting the right drive for a given axis.
FAQ
Frequently asked questions
What control task does a servo drive perform?
It closes a real-time feedback loop around a servo motor's position, speed, or torque, continuously correcting the output so the motor follows a commanded motion profile with high accuracy.
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