im in a pinch at work. we had 2 - 10hp 460v motors go down we had 5inches of rain water got into the peckerhead shorted the wirindg causing both motors to fail. I found the bad wiring. I unwired the motors and megged them both. they showed grounded on each leg. turns out after they dried out in the shop overnight they now show ok. now supervisors looking at me wanting to know what happened. whats a guy to do. if I meg a motor and it shows bad. well ??
I megged a wet motor
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I am not sure how you can meg a motor if it is soaking wet.
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If you Insulation Resistance test a motor (Megger) and one phase is grounded all the phases should be grounded or you have a problem
If a motor is wet it is possible to dry it out, though long term there could be problems with bearings, foreign matter that floated in during the soaking.
If a motor is wet it is possible to dry it out, though long term there could be problems with bearings, foreign matter that floated in during the soaking.
yes all phases showed grounded. it dried out overnight and they are now running them both. makes me look like crap to ones that do not understand how things like that work. it also shorted the wiring out supplying the motors. I found that with megger also. I left that to replace after I got the motors down being motor removal is a 9hr job. when the supervisors get in the motors are dried and ok. they see the bad wiring and automatically assume that was the only problem
I pretwist and then use wire nuts. Solder pots rule.
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The only thing the boss might be mad about is the time it to to remove/reinstall the motor.robbert said:
It's a toss up as to wether it was a smart time saving idea to remove it, or let it sit in place and hope that when it dries it would be ok.
I've done both.
IMO you were a smart for megging it and tagging it out. Like John said, the life of that motor is now shortened. It's just no one knows how long it will last.
There is a PDF book called "A Stitch in Time".
Google it or search here on ET for the link.
It's all about how when and why to use a megger. Great reading.
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You just need to explain the how's and why's of water and electricity.
Tub full of water and extension cord bad, tub empty with same cord no problem.
Tub full of water and extension cord bad, tub empty with same cord no problem.
lol yes indeed !!:thumbsup:
I think the best way here is to explain that since the motors were wet, you tested (meggered) them and they failed the test.
So instead of ordering replacement ones, you decided to remove them and dry them out. Then test them again.
This time, they passed the test, so they were re-installed.
Be sure to state that if they were energized while wet, they would almost certainly fail to the point of needing replaced. The purpose of the first test was to prevent further damage.
So instead of ordering replacement ones, you decided to remove them and dry them out. Then test them again.
This time, they passed the test, so they were re-installed.
Be sure to state that if they were energized while wet, they would almost certainly fail to the point of needing replaced. The purpose of the first test was to prevent further damage.
I pretwist and then use wire nuts. Solder pots rule.
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I vote this as best informative electrical post if 2013.brian john said:
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We would never put a flooded motor back into service. At the least, send it out to be tested, cleaned and baked professionally. Getting wet is one thing, being submerged is quite different. Were they wet from rainwater or were they submetged?
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Can you explain more about this?
If a winding fails when running it means the insulation is compromised to the point where you have current-flow severe enough to operate protection.
If the winding got wet, and you had really tight ground-fault current sensing, it might trip but your motor could be fine when dried.
If the winding got wet and faulted severely enough to take out your overcurrent protection, there's absolutely no way drying that motor out would make it suitable for continued service without extensive repair.
The rule-of-thumb with water and electrical equipment:
If it gets wet while de-energized, it can often be easily saved, but if it gets wet while energized it will often cause a lot of damage.
Also how did you test them and what values did you get?
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I think Robbert did the right thing. But how did this impact production/Reseach?
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Depends on the situation, we have done some fast on site drying to get a facility up and running as emergency measures are taken to obtain new equipment.
Every job is different and depends on the how and whys of what a customer needs, while never taking chances or risking a safe operation.
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You did the right thing.
Next time, if ever again, pull the end bells off the motors, pull the rotor out and put a lit 100w bulb in the windings over night. Change the bearings while you are at it.
Works on stored transformers also.
In the morning, check everything again. If it fails, you saved a lot of possible damage. Your a hero.
If it checks out OK, your a hero.
In other words, dont let nature do your job for you- because nobody believes it when something "just starts working". Especially if you have to explain the "extension cord thing" to them.:laughing:
Next time, if ever again, pull the end bells off the motors, pull the rotor out and put a lit 100w bulb in the windings over night. Change the bearings while you are at it.
Works on stored transformers also.
In the morning, check everything again. If it fails, you saved a lot of possible damage. Your a hero.
If it checks out OK, your a hero.
In other words, dont let nature do your job for you- because nobody believes it when something "just starts working". Especially if you have to explain the "extension cord thing" to them.:laughing:
I pretwist and then use wire nuts. Solder pots rule.
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Sometimes you get very lucky and they start right up while still submerged.
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First of all I agree ! Why are you megging a wet motor ?
Didn't they teach you water and electricity dont mix ?
You should have waited till it had dryed out completely, then tested it !
If there on your back, say it has to dry out first !
sometimes it will do no real damage, if you let it dry out properly.
especially if its clean rain water.
You live, and you learn !
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yeah especially if they are the duck motors(wet location motors):laughing:
http://www.leeson.com/Literature/pdf/1050/ACWashguardWhiteEpoxyStnlsSteel.pdf
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The motors should be raised if there is even a hint of flooding....
Doing preventive measures like that is what separates the smart companies from the lazy ones...
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