I have a Powermatic lathe with a VFD. Lately it has occasionally refused to turn when switched on. It is intermittent, but the issue is becoming more frequent. I will stop the machine to check progress, and then the tool will not spin up. I’ll fiddle with the speed setting, and turn the piece by hand, and eventually it will start again.

?

The lathe is at least 20 years old, but less than 30 years.

?

Not a Felder tool, of course, but perhaps the talented FOG members can help me out. I have no idea where to even begin addressing this, so any suggestions or education will be helpful.

?

Thanks, folks!?

--

John Hinman
Boise ID
Kappa 450X and A941

Might be stopping in between poles on the motor just enough to stall out. Try hand-shifting position a few degrees and compare notes, might also be able to give it a spin by hand and then hit VFD to start. There's always parameters to adjust in the VFD programming, or the possibility you are getting more startup resistance than it was set for originally due to bearing wear or lubrication oil/grease failing some way. Then again, the VFD might just be failing from age, too.

Does the VFD show any error codes?

Is there a way for you to check the VFD with another motor or run the lathe motor with another source?

Unfortunately you cannot measure the VFD output voltage with a DVM but that is another first step in diagnosis. You will need a meter with scope capability or an oscilloscope.

It the VFD part of the original stock lathe??? Or was it an add-on modification??? If the VFD is 20-30 years old, it is entirely possible that the electrolytic capacitors in the VFD power supply have dried up and are no longer able to provide enough current/torque to get the lathe motor moving.

?

-Aaron Inami

I am hoping that John will report back with errors being set by the VFD.

The VFD is original to the lathe, and is in a cabinet under the bed of the lathe.

?

I have never cleaned it. I’ll blow the cabinet with compressed air. It is pretty well protected from the fountain of chips created while turning, but it does get dust through ventilation ports.

?

The user manual for the VFD refers to error codes, but it is not clear to me how to display error codes. Maybe that is supposed to be obvious ….

?

When it did not start this afternoon I looked in the cabinet. No error codes were displayed, but the display said STOP when the switch was actually on. When I turned it off and on again, the display said RUN and the machine started spinning. That makes me wonder if the issue is in the mechanical switch, located on the headstock.

This is what the VFD looks like. The switch is on, so it should not say STOP.

--

John Hinman
Boise ID
Kappa 450X and A941

Brian, the buttons on the VFD panel do not seem to start or stop the operation of the motor.?

--

John Hinman
Boise ID
Kappa 450X and A941

John,

On my VFD the panel buttons are locked when remote operation is selected. I remember that in order to switch between remote and panel operation, I have to reprogram. I would expect the OEM to have done this on your lathe for accidental startup. I think you will need to study the manual to allow panel operation. It is not too difficult to check if the knobs on your machine are working. Typically, there is a connector where low voltage signals (I believe mine are 32VDC) are present for this purpose. You may be able to trace the cabling from the knob to the terminal on the VFD. Polarity wise there are multiple possibilities, but you should see hi voltage (~32VDC) to low?voltage toggle (or vice versa) on the terminal as the machine knob is turned on/off.