Grinder acting crazy

Britt_Askew

Britt_Askew

Knifemaker / Craftsman / Service Provider
Joined
Dec 9, 2010
Messages
1,218
I have had my share of electric motors bite the dust but I have never seen one do this before....running baldor 1 1/2hp and fm50 vfd .... Been grinding for probably an hour and the motor died, I cut the toggle switch to the off position and it starts running again but the speed goes up and down and up and down (with the toggle switch in the off position)? I unplugged the grinder from the vfd and plugged the vfd into my buffer and ran it awhile with no problems. Switched back to the grinder and after about 30 seconds it did the same thing again ? Got any ideas? Nothing smells burnt at all. Could the toggle switch be bad? It is an old 3 way? BUT WAIT the switch worked fine when using the buffer? Guess its time to make sure everything is unplugged and go to bed :)

Here is a picture of one I am working on (still more to do). This is the first time I added a hole in front of the scales and I am not crazy about it
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Check all wires between motoror and vfd. I assume you don't have 3 phase and are using the vfd to go from single to 3 phase. If you know someone that has 3 phase then try the motor connected directly. You could have a wire pinched in 1 of the cords. Since you know that it ran with the buffer then look at the other connections that are not common between the 2. Pinched wire or loose wire connection would my guess.
 
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Also, there may be an issue with load. The grinder is probably a lot more current draw than the buffer. I would consider replacing the switch, as it may be wearing/arcing out.
 
Hi Can you tell me if this toggle switch is before or after the VFD. If it is between the motor and VFD the is not a good thing and will destroy the switch and the VFD over time. I do not believe the Teco FM50 come with a factory installed toggle switch correct? Yet us know either way please

Brett Mathews
Esteem Grinders
 
The yellow wires go to the switch (fw,re,12v)
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Switch is mounted on the grinder.
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The grinder and buffer have a female end on the power cord and the vfd has a male plug.

I tightened up all the connections although none seemed loose. Ran the grinder for a while this afternoon with no problems. Fixing to give it a good workout tonight , will keep my fingers crossed.

Just to make sure I have it wired right - I have single phase power and am using the vfd to get the 3 phase and am running it on a 220 outlet. The 3 phase motor has a low voltage and high voltage way of wiring. Am I supposed to use the low voltage or high voltage way to wire it? It is wired for the low voltage now, is this right?
 
Well you have the switch wired correctly so that is good. As for wiring the motor you are correct you want it wired low voltage. That said I would but the VFD is the culprit and is on its way out. Just as good measure I would remove power from the vfd and wait tell all the light go out and lightly blow it out with some compressed air just to make sure there is no grinding dust in there causing problems.

Good luck
 
Ran it for another couple hours last night with no more problems. If the vfd does quit hopefully I will be able to buy one thats sealed and I dont have to unplug all the time. I have come to really dislike the fm50.

Thanks everybody
 
kb ac drives are pretty nice and their size is reasonable. there are other options but size becomes an issue and cost.
 
You need to build a sealed enclosure for the FM50 or mount it in a room outside of your shop. Metal dust will kill it very fast. Metal dust on the internal points of your VFD is most likely the cause of your erratic experience. PT Doc has a good recommendation. KBAC-27D is a good NEMA 4x VFD that will withstand the environment of metal dust. There are many places to get them but this is one place that I have successfully used --> www.electricmotorwholesale.com

Eric Fleming
www.flemingknives.com
 
A fair enclosure for a non-sealed unit is to mount a plastic storage bin box top on the wall. The ones that are about the size of a shoe box work well. Mount the VFD on the top. Snap the box over it. You will have to make a few slits for the wires, but the enclosure will keep a lot of metal dust away.

Blowing out an open ventilated VFD regularly is important. Use compressed air from your compressor at a reasonable pressure. Don't get crazy with too much pressure or you might blow something loose inside. 30PSI is probably plenty.
 
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Originally I had it in an enclosure but when I moved it to where it is now I didnt bother with it. I mounted it under a shelf about 10' from the grinder thinking that would be enough. I regularly go up to it and blow real good (like blowing candles) and thought all was good. I was amazed to see how much dust the air hose found inside. I will be building a new enclosure this weekend. Thanks
 
Well if its cutting completely out, it might be a loose wire on the input side of the FM50. We use these a lot. Check with a small screwdriver to make sure all the terminal screws are tight.
 
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