electic motor growling

B

brewzalot

501 Club
Need help diagnosing a fairly new 2 capacitor start and run 220v motor on my metal lathe.
At start up about 1 out of 3 times the motor would start but almost immediately growl/vibrate (electrically) so bad that if you left it on for more than 3 seconds it would pop a 20 amp fuse. For a while I was able to jiggle the drum switch and it would stop the growl and run fine. I decided to replace the reversing drum switch , thinking the worn contacts were the problem. But after installing a new one, I still have the same problem only now it does it every time and I cant get it to stop . This happens in both directions.

Both capacitors look good and test the correct microfarads, which is the only test I know how to do on them. I'm thinking maybe the start capacitor is not kicking out? The motor is in a really tough place to access and test, so I want to be sure of my attack plan ahead of time.

Has anyone seen this or have any advice? :lost:

thanks, tim
 
Pull the motor and bench test. Check the bushings/bearings. If the armature has been dragging on the fields, bad bushings/bearings.
 
Well, before pulling and testing the motor, I took the cover off the drum switch and observed more than usual sparking on some of the contacts. Long story short, the new switch was acting just like the old one and needed some tweaking to get the contact arms to mesh properly. Although it was made in New York, its not quite the same quality as the original AB switch. Which would explain why they have NOS switches on ebay for $300-$1000.

Running good now,
thanks Eugene for your reply
 
Sounds as if the centrifugal starting switch is not opening as it should. That would hold in the starting windings too long, causing the overcurrent device to actuate.

This condition ages the motor rapidly.
 
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