AC motor with grounding problem

[Carldar]

I have an A. O. Smith corp AC motor that has ground problem. It is on an air comp. and tank assy that was made in 1956. I was told when I bought it that I could not use a ground on it as it would pop the breaker and that they were meant to be wired with two wires for 115/230v without a ground. It is wired for 220v and I have used it for several years and it did in fact pop the breaker if you grounded it. I put a wire from the motor to a light base and wired the other side of the light to ground so I could see if it ever had a short causing high voltage to ground. The voltage to ground was about 30v. when I moved to a new location I had to reverse the motor wiring to get it running in the right direction. Now there is no voltage to ground and I am able to ground it without poping the breaker. Could it be that there is a winding that is shorted to ground or is this motor really made to work without a ground?

 

[itsmoked]

It doesn't matter much... That is a very dangerous situation... You should further your investigation. It does indeed appear that you have a winding shorted to case.

Do indeed FIX THIS!!

I cannot imagine a motor as new as "56" being deliberately wired some how to ground.

Make sure that some flying wire whisker on some connector isn't touching the case. If none are found JUNK THAT MOTOR.

 

[Carldar]

The real puzzle is that if I wire it for rotation in one direction the frame is hot. If I wire it for rotation in the oposite direction the frame is NOT hot. If there is a shorted winding it is shorted no matter how you wire it. This is not the case here. This motor is not acting like it has a shorted winding to me. Any ideas?

 

[itsmoked]

Start winding is shorted on one end. So the case gets hot based on which side is hooked to the hot verse neut.

Why on earth did you post this in the solidstate relay forum there are a bunch of motor specialists in the MOTORS forum..

 

[Carldar]

itsmoked, what is the web address for the motors forum? I googled for a motor site and this is all that looked good.
It does have a start relay built in to it. Is this repairable or will it have to be rewound?

 

[itsmoked]

Before you go to the motors forum go to the top of this thread you've started. Highlight the "thread956-142808"
and copy it.

Click the "Browse Forums" at your upper left panel under your log in name.

Scroll down the list of furoms to the Electrical Engineering section.

Pick the Motors forum.

Start a new thread in that forum.
Mentiion you mis posted a motor question in the relay section but you would still like comment on it.
Then past the previously copied thread number "thread956-142808".

They can just click on it an read it.