Electric motor is ticking

Reddinr

Reddinr

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The three phase VFD-powered motor on my powermatic wood lathe has developed a ticking sound. It only ticks when powered. When I turn it by hand, no ticking. My fear is that it is insulation break-down in a motor coil and it will destroy the VFD eventually. I had to replace the VFD a couple of years ago so maybe that is a clue. I'm in the middle of making a bowl for a Christmas present but I stopped because I'm afraid for my VFD.

How do I test the insulation for turn-turn arcing? I wonder if an oscilloscope and fast current sensor would work? I know how to test coils to ground but not turn-turn.
 
no engineer or anything but a test with a Megohmer is what they are for. not overly expensive, I have one and used it today to check the primary winding on a transformer. mine will test with 500 or 1000 volts
 
Thanks. I have one of the old hand-crank meggers and tested the insulation from coils to ground and it looked ok. I'm wondering if the arcing (if it is arcing) is from one turn of a motor coil to a nearby turn of a coil. I don't know how to easily test that.
 
Kind of random but a few more ticks when the motor runs faster.
 
Gaaah. New motor is about $950, automation direct. Still have to verify shaft length etc. 145T Frame, 2HP 1725 RPM, 3 Phase.

Will check the belts. They are flat, grooved pulley belts.
 
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How fast are the "ticks"? Take off the belt and listen again
I agree that it may be a mechanical problem not electrical- maybe a bearing?
 
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At slow RPM the ticks are .5 to 2 seconds apart. Going out now to remove the belt and see what happens.
The earth shattering kaboom is what I am worried about. Hopefully it is a belt, which didn't occur to me.
 
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