Did it rotate at all? Can you uncouple the compressor? What make/model compressor?
480V vs 460V
- Thread starter Drod04Mustang
- Start date
Did it rotate at all? Can you uncouple the compressor? What make/model compressor?
Drod04Mustang
Member
- Location
- Avon Park Florida
- Occupation
- Industrial Electrician-Residential Electrician
The first time they turned it on it tripped. Reset the breaker and then it turned on and function. The Air compressor guy said that it was possibly the breaker. He said that it was getting more voltage than it should. I check the other breakers in that same panel and all are around 495, 496.
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zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
Not to put too fine a point on it, but IMHO the AC guy is a bonehead. OTOH, the breaker could be the problem for other reasons.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
A breaker does not determine how much voltage is supplied to equipment. It sounds like your Air compressor guy is simply passing the problem to someone else.
Your breaker has a 100A nominal trip rating. It is built into a 225A breaker frame, so its instantaneous/magnetic trip point is roughly 2250A. It should be good for that motor nameplate with the maximum voltage at 380V 60Hz.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
Has the breaker been tested or swapped with another? That's not clear to me from earlier postings.
ptonsparky
Tom
- Occupation
- EC - retired
Hint: Use an amp meter with Min/Max or Inrush at motor startup.
Drod04Mustang
Member
- Location
- Avon Park Florida
- Occupation
- Industrial Electrician-Residential Electrician
No that is the next step to change out the breaker. Dont have an extra one of those lying around. Ive checked all other breakers in that panel and they all are around 495, 496, 497. I assumed this was correct due to the fact that its 480V with 5%+- which would be from 454V-504V. I dont see anything wrong with it but I guess since they just spent 7 k on a new motor and install they want to have longevity out of it. Thanks for help.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
Keep it clean, lubed, and cool (stay inside the temperature rating) and it should have a long and happy life 
.
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kwired
Electron manager
- Location
- NE Nebraska
Motor probably will last longer if supply volts is 495 than if 465.
Voltage is in acceptable levels but would check it during a weekday when building has loads running and a few times at night & /or weekends. Have came across three phase voltages 509 to 507 volts late at night and weekend but very close to 480 to 483 volts with loads running. Like another post said would run the motor with coupling removed from compressor. Then see if it runs. Not sure but unable to remove motor from compressor ask the HAVC /Refrigeration tech if they can make the compressor run unloaded. Years ago I had a 400 HP trip out the circuit breaker on a centrifugal compressor. That type goes thru a gear box that increased speed to over 6,000 RPM. It was attempting to start while fully loaded. Best practice is always to see how easy a rewound or motor that was worked in ( new bearings ) turns before installing. I usually do not take voltage readings to neutral on three phase motors. Did you megger the motor?
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Motor is rated 46.8A, breaker is a Sq.D. KH3600 rated 100A, with the instantaneous trip setting adjustable from 500-1000A. What is it set at? Under the rules in article 430, you can set the mag trips at up to 1300% of the motor FLA if you can show that it nuisance trips below that. 1300% of 46.8A is approx. 600A. If it is a newer “Energy Efficient” motor, it can be set as high as 1700%, which would be approx. 800A.
Don’t jump to assuming that the breaker is “bad”, it was just likely not set correctly and when the motor was rewound, the magnetizing inrush is now a little higher. Details matter…
Don’t jump to assuming that the breaker is “bad”, it was just likely not set correctly and when the motor was rewound, the magnetizing inrush is now a little higher. Details matter…