VFD Problem

fitzo

fitzo

Gold Member
Joined
Aug 14, 2001
Messages
6,648
I have one of Rob Frink's KBA controllers on a 2 HP KMG. Today I noticed that the power light stays on even with the power switch in the "Off" position. Unfortunately, it's not just the indicator...the motor starts and stops also.

The immediate conclusion is that the power switch is bad. I've unplugged the unit and let everything discharge just to see if it's flaky electronics, but plugging it back in returns to the same problem. Makes sense if it's a mechanically faulty switch.

Does anyone have any information or ideas other than that obvious "bad switch". I'll call Rob Monday, but thought I'd run it by the folks here in the meantime.

Thanks.
 
Do you have a proper sealed VFD ? If not the grinding dust is shorting things out.
 
It's NEMA4, and only several months old.
 
Last edited:
It's the switch. I did what I should have in the first place. Popped the case open, disconnected and checked continuity on the switch. Zero resistance both poles, on or off position. Guess that means I need a new switch. :)

Thanks for the help!
 
Mike - when you stop/start the motor, you do that with the dedicated start/stop momentary contact switch - not by toggling the power switch ?

Lowes/HF/Rat Shack all carry what you need - a DPST switch. I had some bad luck
with Rat Shack's variety once. Make sure to keep the rubber boot on the switch .

McMaster has everything you need - as long as you can wait till next week :)
 
Mike, yep, it sounds like your power switch has gone south. The drives don't come with them from the factory and I include them at no charge because I think it's an importatnt feature.

While I have no idea why yours went bad, perhaps it was made on a Monday, it's an easy fix and I'll send a replacement right away. In the meantime, just disconnect the power elsewhere when you are not using the drive.

Have a great holiday weekend.

-Rob
 
Thanks, Rob, I appreciate the replacement! It's an easy matter to unplug it until then when not in use.

Rashid... yes, I toggle the motor "Off" with the Start/Stop, then switch the power off once the motor's halted. Because it is different than the single-switch DC VSs on several other machines, I even made myself a little cue card Post-It stuck to the controller to remind me until it becomes habit. A precaution to help overcome aging-related CRS. :)

Thanks, again, for the help. I should have checked the internals on the VFD before I posted this thread. My initial concern mirrored Steve's comment that perhaps I had a board level failure, so I sought recommendations first in a moment's worry. I am very happy that it was the simplest of problems to diagnose and repair.
 
Last edited:
Fritzo,

I appreciate your posting this thread. Even though it may not be that major, it all adds knowledge to my very steep learning curve...to learning, setting up and making knives.

Mahalo (Thanks), Phil
 
I just wanted to write the final chapter of this by sending out a BIG THANK YOU to Rob for the kindness of his wonderful service. The switch got Fed-Ex'd his first day back from the holiday weekend (Monday) and arrived today. 5 minutes to install and I'm running just perfect again.

Can't get better help than that, anywhere. Thanks, Rob, I appreciate it!
 
You must log in or register to reply here.
Back
Top