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VFD Working, but Grinder Not Turning On

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Stark Knives, Nov 30, 2020.

  1. Stark Knives

    Stark Knives

    Mar 19, 2010
    I’ve been running my grinder with no issues for a while, but today while I had the grinder running, the drive wheel just stopped rotating. The VFD appears to be functioning normally (the light goes green when I turn it on like normal and I don’t get any error lights) so I don’t think it is a fuse this time. Are there any particular things I can try to fix this? Maybe a connection from the motor to the VFD that I should check? Let me know if there is any other information that might be helpful.

  2. Drew Riley

    Drew Riley Riley Knife and Tool

    Oct 17, 2007
    What kind of VFD do you have? I assume you've tried turning it off (like 30 seconds) and then back on?
  3. Stark Knives

    Stark Knives

    Mar 19, 2010
    I believe what I have is the KBAC 27D. And yeah I left it unplugged for a couple of minutes and that didn't seem to help unfortunately. :(
  4. SBuzek

    SBuzek KnifeMaker Knifemaker / Craftsman / Service Provider

    Dec 7, 2006
    Check and see if you broke your key or it fell out.
    DevinT likes this.
  5. Stark Knives

    Stark Knives

    Mar 19, 2010
    How do you check that? Sorry, I don't have much technical experience with electrical/motor work haha!
  6. Drew Riley

    Drew Riley Riley Knife and Tool

    Oct 17, 2007
    I'm going to assume you have a direct drive grinder? If so, then your drive wheel is mounted directly to your motor's shaft. In both the outer center periphery of the shaft, and the inner bore of the drive wheel, there will be a square(ish) cut out. A piece of key stock (key) presses into this to "lock" the wheel to the shaft. Otherwise, the shaft would just spin inside the bore of the wheel.

    Think of your drive wheel as the bushing in the pic above.

    At any rate, you should be able to see if your motor shaft is spinning. If you're drive wheel isn't moving at all, I have a hard time believing the motor is spinning, even if the key were to fall out, but it's still worth checking.

    Does your KBAC have a forward/reverse switch? Is it possible that it inadvertently got switched to the stop position?
    If not, try spinning your drive wheel/motor shaft by hand while the VFD is switched on. It's possible that you dropped a phase of your motor (one of the 3 motor leads could have come loose) and you're not getting rotation due to that. Sometime if you "help" it forward, it will take off. It probably wouldn't hurt to check that all of your connections are still tight. Grinders vibrate, and things get loose.
    DevinT and SBuzek like this.
  7. Stark Knives

    Stark Knives

    Mar 19, 2010
    Thanks for that explanation! I was able to spin the drive wheel by hand, but it still wouldn't run with the VFD on. I also checked the wires that were easily accessible and couldn't find anything loose. I wasn't sure how to totally disassemble the motor to check the insides, so maybe I'll have to bring it to someone to have a look at.
  8. Outdoor Gear Dad

    Outdoor Gear Dad Gold Member Gold Member

    Jun 1, 2019
    Do you have a way of bypassing the VFD and connecting the motor directly to a power outlet to see if it’s getting power and functioning?
    I guess if you can isolate the problem to either the motor or VFD that would help with next steps.
  9. Stark Knives

    Stark Knives

    Mar 19, 2010
    I could try that! Do you happen to have a link or something that might explain how to test that out? It's times like this that I wish I were a bit more knowledgable about this type of thing....
  10. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    I will just say what many I am sure are thinking.

    If you don't understand three phase, VFDs, and using an ohmmeter/voltmeter ... get someone who does to test for the problem. The checks should take less than 5 minutes for someone who knows what they are doing.

    The tests will be:
    Check all switch positions
    Check all fuses and breakers
    Test incoming power at te VFD on both legs and any neutral line
    any ground lines
    Test output from the VFD at the motor
    Read the resistance between all three phases
    Ken H> likes this.
  11. Ken H>

    Ken H>

    Dec 31, 2011
    Stacy has it right - No reflection on the OP but he doesn't seem to have the electrical knowledge to be doing much testing at all. The motor will NOT run with bypassing the VFD since the motor is a 3 ph motor and odds are it's a 1ph supply. If the key was slipping he would still hear/feel the motor running. It sounds like there is no output from VFD - get someone with proper test equip (DVM) and knowledge to test the system out.
    Natlek likes this.
  12. Stark Knives

    Stark Knives

    Mar 19, 2010
    No need to worry about slighting me, I am well aware of my shortcomings when it comes to this type of stuff! :p
    I'll try to take it somewhere in the future. What type of place would you recommend me bringing it to? Would somewhere like Ace Hardware or Home Depot be able to do that, or would it be better to go to a more specialized type place.

    Thanks for all your help everyone, I appreciate it!
    Ken H> likes this.
  13. Drew Riley

    Drew Riley Riley Knife and Tool

    Oct 17, 2007
    Probably need something like a motor repair shop to check it out, though you may not need to get that specialized. If you know any millwrights or electricians, they could probably troubleshoot it fairly easily. Bring it to Northwest Indiana and I’ll look at it. :D
    Stark Knives likes this.
  14. kdnolin

    kdnolin Basic Member Basic Member

    Jan 16, 2017

    Here is a video on how to test a 3 phase motor. DISCONNECT FROM VFD OR ANY OTHER POWER SOURCE BEFORE DOING ANY OF THESE TESTS!
    Stark Knives likes this.

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