# Servo Motors/Drives with a Disconnect Switch?



## John Valdes (May 17, 2007)

Absolutely. Never* place any kind of switch on the load side of any VFD or servo controller.
Now, you will hear from others the NEC requires a disconnect at the machine/motor and that is true.
I personally do not like to interrupt the drives output in any way, including the blades of a disconnect.

If you must do it. Do it with a logic circuit that ensures the servo control is powered down before you can open a switch on the load side.

Best case scenario is the OCPD is lockable and in direct sight of the servo motor.
This will allow locking, but preserve the direct connection between the drive and the motor.

* Subjective comment.


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## Paulusgnome (Mar 28, 2009)

Wouldn't put a disconnect between servo amp and motor.
To meet US regs, we have put disconnect switches adjacent to VFD-controlled motors. Since this can damage the VFD if it is driving the motor when switched, we would use an early break aux contact to signal the drive to shut down ahead of the break in the motor circuit.


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## Peewee0413 (Oct 18, 2012)

Disconnect with early break is correct.


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