Megging Motors

[puckman]

I had a discussion with a electrician on megging motors .His Idea is to meg only when motors are a problem and I thougt it should be about once a year to follow the condition of the motor. Is there a perfered method? Which megging should be done ? [dar]?

 

[ptonsparky]

Megging a motor after the smoke is gone is the normal process. Most places operate on the run til dead theory and that may very well be suitable.

Processes that do not tolerate unexpected shutdowns could most definately profit from a PM program that would include Megging as part of the routine.

 

[brian john]

A complete PM program would include regular testing of motors and tracking the readings. Then with regular readings you could determine possible failures and in lieu of the process being suddenly shut dow from a motor loss, planned outages are utilized to minimize down time. The questionable motor could be replaced with a new motor and the existing motor sent out for a rewind, or any other possible required maintenance.

 

[hardworkingstiff]

When you meg a motor in an existing system, do you disconnect the wiring at the motor and just check the motor or do you check the motor and wiring from the load side of the starter? If from the load side of the starter, may you just check (with power and controls off) from the load side of the starter without disconnecting the wiring?

 

[puckman]

When I MEG iT Is usually from the starter load side. Circuit breaker is lockout and load side wires are removed from starter. It is for 1 minute and second time for 10 minutes. Sometimes we meg right at the motor if a diconnect is at motor location. Really not sure if this is right or wrong way to do it.

 

[ptonsparky]

I remove the wires from the load side of the starter and meg from there. You don't have to remake the motor connections each time this way. If it fails from there, isolate the motor from feeder and meg again.

 

[zog]

Both the NFPA70B and ANSI/NETA have recommended testing intervals, you can download at www.netaworld.org.

The most valuable thing about megging motors is the trending. But, if you do not tempature correct your readings they are worthless for trending so be sure to include the winding temp and adjusted meg reading in your records.

 

[wptski]

I retired from the auto industry and they seem to be the worst or have little or no PM programs! It appears that only certain industries have PM programs of any kind.

 

[puckman]

Does anyone know where or how to do the temperture correction when megging ? Checked the neta world and that seems to be a pay web site something I can't do at this time.Thanks

 

[zog]

Does anyone know where or how to do the temperture correction when megging ?

See attachment, this is for 40C correction used for motors and generators only, all other equipment gets corrected to 20C.

Checked the neta world and that seems to be a pay web site something I can't do at this time.Thanks

The frequency of maintenence tests is what you need and the reason I sent you there. Right on the front page it says:

Frequency of Maintenance Tests

Click More for a free download of the Frequency of Maintenance Tests - Appendix B

 

[zog]

I retired from the auto industry and they seem to be the worst or have little or no PM programs! It appears that only certain industries have PM programs of any kind.

They did plenty of PM's. thats all I did for 10 years is PM of power systems in Ford and GM plants in the Detroit area. They decided it is better to hire certified testing companies to come in on weekends vice buying all the test equipment, training the skilled trades guys, and dealing with all the UAW games.

You had a good PM program, they just did not tell you about it

 

[wptski]

They did plenty of PM's. thats all I did for 10 years is PM of power systems in Ford and GM plants in the Detroit area. They decided it is better to hire certified testing companies to come in on weekends vice buying all the test equipment, training the skilled trades guys, and dealing with all the UAW games.

You had a good PM program, they just did not tell you about it

Nope, I'm refering to PM programs in the plant. They had some PM programs that were started by people and when not performed, people caught hell. As the people who started them, watched them retired or moved on, the programs were slowly phased out. Another thing is that it's easy to shut down a single machine for PM but trying shut down a assembly line that makes or loses $27,000/hr is impossible.

 

[zog]

Nope, I'm refering to PM programs in the plant. They had some PM programs that were started by people and when not performed, people caught hell. As the people who started them, watched them retired or moved on, the programs were slowly phased out. Another thing is that it's easy to shut down a single machine for PM but trying shut down a assembly line that makes or loses $27,000/hr is impossible.

I did entire plant outages nearly every weekend in Detroit at the auto plants, holidays too. In fact my first Thanksgiving with the family was last year. Usually that was a shut down day.

 

[wptski]

I did entire plant outages nearly every weekend in Detroit at the auto plants, holidays too. In fact my first Thanksgiving with the family was last year. Usually that was a shut down day.

What exactly did you do? What Ford plants if any?

 

[puckman]

Sorry for all the questions on this subject , I am not very knowlegeable with megging.
If the motor to be megged is below water [sump pump motor] would my temperture correction be that of the water ? I know of no other way to get winding temperture if there is no thermo coupler connected to the motor. The motor could be large and a problem to remove.

 

[zog]

What exactly did you do? What Ford plants if any?

Cable testing, transformer, breaker and switchgear PM's. All Ford plants, including Wayne, Truck, and ISA in your area, Wixiom, Romeo, etc......

 

[wptski]

Cable testing, transformer, breaker and switchgear PM's. All Ford plants, including Wayne, Truck, and ISA in your area, Wixiom, Romeo, etc......

Okay, I wouldn't even consider that to be like the plant PM programs that I'm refering to which goes by each individual plant.

 

[jaredx9]

At our plant we meg critical motors as often as possible. Then we get whatever else we have time for. There is no good time schedule to meg motors because they can fail anytime.

I would say find your critical motors and meg those as often as possible, then pick up whatever else you can. Meg testing doesn't really tell you everything you need to know. Investing in a motor tester that does surge, hipot, step voltage, meg, and winding resistance, is the right way to do it.

We have a pretty solid PM program with two guys dedicated to motor testing, and infrared/ultrasound. These guys more than pay for themselves each year. Finding one bad motor before it fails is payback enough.

 

[zog]

At our plant we meg critical motors as often as possible. Then we get whatever else we have time for. There is no good time schedule to meg motors because they can fail anytime.

I would say find your critical motors and meg those as often as possible, then pick up whatever else you can. Meg testing doesn't really tell you everything you need to know. Investing in a motor tester that does surge, hipot, step voltage, meg, and winding resistance, is the right way to do it.

We have a pretty solid PM program with two guys dedicated to motor testing, and infrared/ultrasound. These guys more than pay for themselves each year. Finding one bad motor before it fails is payback enough.

I agree, a real motor PM system includes much more than just a megger test but many places have to play witht he cars they are dealt. I don;t deal with motors anymore but when I did we used the PdMA equipment.

http://www.pdma.com/PdMA-products.php

 

[mbeatty]

I retired from the auto industry and they seem to be the worst or have little or no PM programs! It appears that only certain industries have PM programs of any kind.

In the Navy, we had very stringent schedules for Preventive Maintenance which included megging and trending of motors, generators, etc.. I tried to incorporate a program as a plant maintenance manager but was always fighting production schedules for equipment downtime. A properly run program saves time, money and can save lives.
Regards,
Mark