Problem- Servo controller on inverter duty 3 phase

[kdoney]

Can I just slap an encoder onto a good inverter duty ac motor, which has the proper inertia data, and get the proper position control? I want to be able to stop the motor at a certain position for 3rd and 4th axes on a lathe.

[mike_Kilroy]

yes & no.simple answer huh?

yes, an encoder will tell where the motor is and a good vector sensor feedback vfd will position it to within a count or two of the encoder.

Do you need to hold position then? If so, you will likely overheat the motor: remember, the induction motor requires 1/3-1/2 nameplate rated current to make a magnetic field to be a motor and thait current generates heat. without the internal fan rotating, the motor will overheat quickly at less than like 1/3 nameplate speed. This is why a servo motor with magnets is most often used instead - no current to make magnetic field so no extra heat sitting still.

Will the $ 300 generic vfd do the job for you? Prob not to your satisfaction. Our servo like vfd sensor vfds cost like $ 1500 instead and do this.

So why not use a servo instead? (email me sales@KilroyWasHere.com and I will quote you both for reference if you want)