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Need Help - Electric Motor Hot?
Posted: Thu Apr 21, 2011 10:47 pm
by gunner66
I have an old 1957 Greenie with the original 3/4 hp motor. I put about 1/2 cc grease in each shielded bearing (grease had dried out, but the bearings seem o.k. otherwise). After greasing, the bearing rotated easily with minor resistenace, but not absolutely "freewheeling" (like a dry but otherwise o.k. bearing). I blew the inside with compressed air and it was was very clean. My question is:
I am running it on my workbench and the entire motor's case seems to be hot to the touch after 20 minutes (can hold palm on motor and not burn hand, but is above "warm"). The area around the bearings don't seem to be any hotter than the rest of the case. Is it normal for the motor to run and be hot to the touch? My only concern right now is that the motor is hot because the bearing are perhaps putting a load on the motor. Thanks for your help.
More info
Posted: Thu Apr 21, 2011 11:55 pm
by gunner66
Here's some additional info:
It is the General Electric motor. The placard does not provide the "amps" it should draw and the "temp rise" field is blank.
Perhaps someone knows the approx. amps it should be drawing at "no-load" or "load"? (I have an ammeter). Thanks, Chris in Georgia
Amps
Posted: Fri Apr 22, 2011 12:05 am
by gunner66
More info: on the bench, it is drawing 8.4 amps at no load.
Posted: Fri Apr 22, 2011 6:36 am
by dusty
The motor housing does get warm. If you can place your hand on the housing and not have to pull away, I think the motor is OK. I have some charts, somewhere, that show current draw on my motors. When I locate them, I'll postscript to this thread..
Posted: Fri Apr 22, 2011 7:48 am
by wa2crk
The 1 1/8 HP motors have a fan sheave on them to move air around the windings and I believe that the 3/4 HP motors are the same. If you run the motor without the fan sheave attached I remember that the frame gets warm within a few minutes. Without the fan sheave a bench test is a different set of circumstances than normal running. Is the centrifugal switch working properly?
Bill V
Posted: Fri Apr 22, 2011 9:07 am
by garys
I found an NEC motor amperage chart. They show full load for a 3/4hp motor to be 13.8 amps, so you are probably OK with no load of 8.4 amps.
http://www.electricmotorshop.net/index. ... Itemid=249
Posted: Fri Apr 22, 2011 10:29 am
by gunner66
Thank you everyone for the quick replies:) . The capacitor, and start relay seem to working properly. The motor starts easily, runs smoothly at its normal rpm, and when I chop power it winds down appropriately.
I have learned so much about using and maintaining my SS from this Forum - thanks to contributors like yourselves. My "greenie" has always been my favorite tool!
Thanks again, Chris in Georgia