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New 460-V Motor Tripping Breaker Fed By 575-V Source

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Ravenvalor

Ravenvalor

Senior Member
Location
Piedmont region of NC
Hello,

My textile mill customer called me this morning complaining that their new sprinkler system jockey pump and motor is tripping the breaker. They just sent me some pictures of the new and old motors and everything looks similar with the exception of the fact that the old motor was 575-volts and the new motor is 460-volts. I know that they have 575-volts in the building so I am not surprised by that. I was just wondering whether or not a 460-volt, 3-phase, 3-HP motor would run properly if being fed with 575-volts. It's just a little shocking to me that someone would make such a bad error as to get the voltage on the replacement motor incorrect. Plan to go out there later on today and assess the situation. If anyone has any ideas I would greatly appreciate the advice.

Thanks,
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
At 25% over voltage I imagine the smoke leaked out.
No real excuse but so few folks are familiar with 575 volt.
I glanced at some jockey pump catalogs and they don't even list 575v as an option.
 
H

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
ptonsparky said:
I have never seen 575.
No, I wouldn't expect it to work.
A VFD of that size would be reasonably priced, if you can find one in that voltage locally.
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I think 575 is common for our friends to the north. I wired a sheet metal fabrication shop in Atlanta, that brought in a bunch of Canadian equipment that was 575 volts. The plant had a 120/240 volt delta service, so I had to backfeed a 480 to 208 y transformer, as Georgia power wanted something like $60,000 to add the service voltage. Voltage hit right on the money.
 
petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
hillbilly1 said:
I think 575 is common for our friends to the north. I wired a sheet metal fabrication shop in Atlanta, that brought in a bunch of Canadian equipment that was 575 volts. The plant had a 120/240 volt delta service, so I had to backfeed a 480 to 208 y transformer, as Georgia power wanted something like $60,000 to add the service voltage. Voltage hit right on the money.
Click to expand...
I put some equipment into a plant down south somewhere one time that was 575 V. I think it was a pulp plant of some sort, but it was a long time ago so it might have made baby food. :)

I would guess the stuff I have been involved with that went to Canada was about half 480 V and the rest 600 V.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
At 600V source to a 460V motor (130% over voltage), you are over saturating the motor windings. It will run, but will run VERY hot, so they likely fried the motor winding insulation. In addition, the starting torque from that over fed motor would be 170% of normal, so instead of starting torque being 160% of full load torque, it would be closer to 275% of FLT! It may have cause mechanical damage to couplings, mounts etc. I would suggest to them that they replace everything.
 
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