Chipmaster motor wiring

It is not recommended to do any switching on the output of most VFDs. I suggest that you check with the manual for the VFD that you have. You normally have the forward ,reverse and stop controls together with the speed control potentiometer mounted in a convenient position away from the VFD. The wiring between the controls and the VFD is only low voltage and current so thin multicore wire is used. It is probably possible use the old forward/reverse/stop controls connected to the control inputs of the VFD. using the old controls in this way may give problems as sometimes the contacts oxidise when there is no cleaning action that occurs when switching high voltages.

Les.

If you forget and open the switch between VFD and motor while running it can generate an inductive spike that destroys the output transistors. Much better to make a direct connection and do the switching and control on the control side of the VFD. For one thing you can usually set the VFD for a controlled accelerate/decelerate time - no need for a clutch.

It won't be so relevant on a lathe, but on a mill for tapping it's convenient to have the motor set for running slowly (say 10 Hz with a large belt reduction), then bring the tap down so it's just resting on the top of the hole, switch on in forward, run the tap to the desired depth then just switch from fwd to reverse. The VFD will happily bring the motor to a controlled stop then reverse with no drama. Try doing that with a normal reversing switch on the VFD output and it would definitely object!