Marginal Megaohm Reading 150 HP

Status
Not open for further replies.
Saturn_Europa

Saturn_Europa

Senior Member
Location
Fishing Industry
Occupation
Electrician Limited License NC, QMED Electrician
The motor is an open case drip proof, 150 HP that runs deck hydraulics on a ship. The megger reading was 0.90, 0.85 and 0.79 megga ohms. Its not faulting to ground and is still in operation. Its just really low compared to other motors.

The motor is at least 10 years old. Replacement motors are 10-12K.

I am worried that the insulation on the stator is breaking down and will fail in the near future.

Replace the motor? Send it to the motor shop? Or tare it down, replace the bearings and bake the stator to drive out any moister?
 
Saturn_Europa said:
The motor is an open case drip proof, 150 HP that runs deck hydraulics on a ship. The megger reading was 0.90, 0.85 and 0.79 megga ohms. Its not faulting to ground and is still in operation. Its just really low compared to other motors.

The motor is at least 10 years old. Replacement motors are 10-12K.

I am worried that the insulation on the stator is breaking down and will fail in the near future.

Replace the motor? Send it to the motor shop? Or tare it down, replace the bearings and bake the stator to drive out any moister?
Click to expand...
That motor is worth the maintenance. Do what you can yourself, then motor shop. Have a spare available.
 
I don't see how replacing the bearings is going to do any good unless they are just bad and need to be replaced. I don't think baking it is going to do any good either.

Based solely on a single reading I'm not sure you can say it is gone bad but it doesn't look good. It might be time to send it off to a motor shop for better testing and possible rebuild.
 
First why besides a penny pincher would ever accept an open motor for such duty. Company that I worked for back in the 1980's had two critical supply fans that were also open drop proof. They only ran one at a time a kept s 5 KW heater blowing on the motor that was not running. They refused to change back up fan to primary at least once a week so the spare would not run for months. And we would have low meggers reading on spare. Finally they purchased something that sent power to one set of windings while motor was off. Produced enough heat to keep high moisture in that area from forming water on windings and motor frame was a few degrees warmer then the room. I always purchased TEFC motors when ever possible. I would send this motor out to a good motor shop to have them go over it. If they rewind it ask them how much more of a charge for think it was called epoxy dipped winding. We had a 20 HP that was mounted at the bottom of a 200 gallon milk tank. Within 8 months seal would fail and milk got into windings burning motor out. We asked the motor shop what could be done to have motor last longer. They coated or dipped the windings with believe they said epoxy then maybe a vacuum chamber. Motor lasted three times longer with the epoxy.
 
Status
Not open for further replies.
Top