Could you ask your friends if you don't know

  • #1

Main Question or Discussion Point

Again, two identical Air Compressors, interlocked=working alternatively=one ON another one OFF=then again second one ON first one OFF, etc.

MOTORS SPECS;
power supply=600V each motor
phases=3 each motor
rpm=1725 each motor
amperage=24A each motor
HP=25 each motor
fuses=3 fuses=60 Amps each for each motor (time delay fuses)

Now; One of the compressors is blowing a fuse very often.
Another compressor never, never blows a fuse.

Question= what to do about this compressor that is burning fuse so often?

It is confusing that just one fuse on one compressor is burning although both compressors as i did say are interlocked, same purpose, same duties. Simply everything is the same. Thank you very much for your attempts.
 

Answers and Replies

  • #2
Danger
Gold Member
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I've never had any exposure to 3-phase, so first I must ask if the 3-fuses-per-motor thing means that there's one fuse for each phase? Are they separate coil setups? In any event, the compressor that's blowing fuses obviously has a defect in it's coil structure, internal connective wiring, or perhaps bearings or something in the mechanical section that drastically increases its internal resistance. Try running resistance checks on the windings first. If they're normal, check out the compressor part itself for things like bad bearings, bend wrist-pins, obstructed valves, etc.. If you can't find anything wrong, replace the motor. If the new one blows fuses too, then the problem is elsewhere. If not, the original motor is bad.
Oops! I just remembered that you should check your input voltage as well. If there's a controller of some kind, it might be overloading one motor. (Not likely, but why overlook any possibility?)
 
  • #3
FredGarvin
Science Advisor
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I'll echo pretty much what Danger mentioned. I would monitor the inrush current to both motors. to see if it is a start up phenomena or if it is during peak demand of the compressors.
 
  • #4
Averagesupernova
Science Advisor
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The first thing I would check is to make sure the motor is wired for the voltage it is receiving. I have worked on equipment that has one phase wired for a different voltage then what it was supposed to be wired for.
 
  • #5
Danger
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Averagesupernova said:
I have worked on equipment that has one phase wired for a different voltage then what it was supposed to be wired for.
Wow! That could cost somebody his next raise. Is that a motor manufacturing defect or something to do with the installation?
 
  • #6
dlgoff
Science Advisor
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Sounds like you need to have the motor checked for a short. It's probably a winding set grounding to the frame.

Regards
 
  • #7
russ_watters
Mentor
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Time-delay fuses tend to rule out start-up spikes, but measuring the amperage of each phase under operating condititions is the natural starting point.

Regarding their operation - they are manifolded together? Do they show the same performance under operating conditions (ie, the system pressure/flow are the same)?
 
  • #8
berkeman
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Does the one compressor still blow fuses when it is run alone and not manifolded with the other compressor? If it runs okay stand-alone, I would suspect a problem with the manifolding or timing of the overlap.
 
  • #9
compressors never work together; one at the time, they are cycling; one finishes and then when air pressure is lower, another one starts, and then again the same thing. I can see I don't express myself clearly enough, but what is confusing everything is the same but one is giving problems.
 
  • #10
FredGarvin
Science Advisor
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You have to get over the "sameness" idea. Granted they are identical models etc...but that doesn't mean that one can not have a problem with it and the other not. You need to do basic electrical troubleshooting. Once you do that, look towards the compressor itself.
 

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