We’re making a run of chairs with a lot of turned parts. From time to time on startup the motor will make a loud humming/buzzing noise; we think it happens usually when work has been underway for a good while, but I’ve certainly used the lathe for extended periods before and never had a problem. This morning the buzz/hum started on startup, the lights flickered, and the breaker tripped. Happened twice.
The motor is rated at one hour (not continuous), but as I said I’ve often run it for longer than that without trouble. After tripping the breaker I pulled the electrical covers off; the motor itself is warm but not hot. There’s no heat or smoke anywhere else– wires, starter etc. I would have expected the overload protection to trip the starter, not the breaker; is there something I’m missing with overload protection, or is there something wrong with my rig? Does a motor pull more starting amperage when it’s warm than when it’s cold?
Technical details: Rockwell 46-450 lathe, the big one. It’s wired 110V but convertible to 220V. Has LVC starter controlling Baldor/Rockwell motor. Nothing else was running on this circuit, which runs #12 wire to a 20 amp breaker. I don’t remember the nameplate amperage, but I know I checked everything out thoroughly before plugging in. I can convert to 220V, running #10 wire to a 20 amp breaker.
Thank you in advance for any help you can give.
John Casteen
Replies
I've had the buzzing problem with tools that make a lot of dust that can get into the motor. The dust gets onto the contacts of the centrifugal switch of the starting relay and it doesn't make contact to switch into the full speed running mode. I'm sure a motor guy can explain it better. I've used the air gun to blast the dust out. It works better on some motors that on others. I hope this is a help.
If your motor is sealed so that dust can't get in through the cooling vents, disregard this post.
BJ
BJ,
Thanks. I should have thought to mention that the motor is TEFC-- otherwise, dust in the contacts or elsewhere would have been a good place to look.John Casteen
http://www.fernhillfurniture.com
When it comes to motors and buzzing noiese, who knows. I have had to replace bad capacitors that left the motor just buzzing. I've also had em smoke before as they buzzed and burned up. No advice, just experience to share here.
Don
My dust collector exhibited the same behavior, humming, tripping, and falling down on the job. (Sounds like an old BF who liked his rum, come to think...) Anyway, the proximate problem was the capacitor, but as i recall we changed out the switch, too, since it's a Grizzly and they are prone to bad switches. I remember the bill came to about $80 for parts and labor, but it's been running flawlessly for at least 6 years since the repairs.
Edited 8/31/2002 12:30:11 AM ET by SPLINTIE
Splintie,
Thanks. I hadn't thought about the cap. Does anyone know how to check the health of one, assuming it's still more or less working?John Casteen
http://www.fernhillfurniture.com
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