HomeFAQCan a VFD control servo motor?

Can a VFD control servo motor?

Using variable frequency drive (VFD) for the servo application is quite possible, provided the application is less demanding in critical positioning purpose.

Servo motors have different information on motor control, it includes rotor positioning feedback, VECTOR mode, requires motor recognition and not necessary and encoder for rotor feedback, it estimates it through output current. (which includes V/F also) Numerical Commands can set V/F setpoint on power modules usually.

When you have VECTOR and Torque control, you may have a torque setpoint, instead of speed setpoint, if there's no load on this mode, the motor speeds up fast and may damage mechanics. If you control Torque, with the same power, speed becomes uncontrollable, some applications combine torque and speed setpoints for different frequency / torque ranges.

The problem here is that we are trying to define a specific answer using very general terms. A servo motor can be an induction servo, a brushless servo, a reluctance servo a dc servo - each of these can be either linear or rotary and can come with a variety of feedback such as tachometer, resolver of various pole counts, incremental or absolute encoders discreet or serial interface with different bus options, laser feedback, halls etc.

Then you come to the term variable frequency drive. Brushless servo amplifiers are also vfds. Do standard inverters have proper control of induction, and brushless motors. Some allow for a software switch, some allow for a firmware download, some don't. Will inverters accept feedback - some have it built in, most that allow it do so by option cards, many do not.

So, I believe if you have a specific situation, you would be better served by a specific question. All of the variations - and I only named a few, will give you countless permutations of answers.

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