VFD Working, but Grinder Not Turning On

Stark Knives

Stark Knives

Joined
Mar 19, 2010
Messages
1,154
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.

Thanks!
 
What kind of VFD do you have? I assume you've tried turning it off (like 30 seconds) and then back on?
 
Drew Riley said:
What kind of VFD do you have? I assume you've tried turning it off (like 30 seconds) and then back on?
Click to expand...

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. :(
 
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.
machinedesign_com_sites_machinedesign.com_files_uploads_2015_02_ShaftConnectionsFig3.png


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.
 
Drew Riley said:
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.
machinedesign_com_sites_machinedesign.com_files_uploads_2015_02_ShaftConnectionsFig3.png


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.
Click to expand...

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.
 
Stark Knives said:
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.
Click to expand...
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.
 
Outdoor Gear Dad said:
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.
Click to expand...
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....
 
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
Check any ground lines
Test output from the VFD at the motor
Read the resistance between all three phases
 
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.
 
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!
 
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
 
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!
 
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