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Can You Run a Servo Motor with a VFD Not so Fast
By Jade York
Can you run a servo motor with a VFD? First, lets look at how a servo amplifier works with a servo motor.
A servo amplifier actually fires DC voltage into the three phases of a servo motor. Each time a phase is fired, it is completely dependent upon rotor positioning reference to the stator windings to be fired. In other words, you need commutation to run a servo motor. Most servo motors will have an encoder that is coupled to the rotor and aligned to give rotor positioning reference to stator windings.
We have actually ran a Yaskawa servo motor open-loop on a variable frequency drive (VFD) The results were not good. You see, no matter how we tuned the drive, the end result was a very inefficient motor that drew high amps and had no torque.
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