I am a maintenance man but I do hold a journeyman's license I'll do my best to explain what is going on. I have 2 ea 50 Hp air compressor. one is approx. 2 yrs old (Com-05) the other is 20+ (Com-01). I seem to be having similar problems with both.
We are running 240 VAC 3 phase into the building to a 400 amp I-line from there a 150 amp breaker carries power to a 200 amp disconnect. with 150 amp fuses. from there it goes to a switch box that allows me to select which compressor I want to use. Com-01 the older one will run for 5-6 hrs. then it will trip the motor overload in the cabinet. by the time I get there (5 Min) I am able to reset the overload and it will run for a couple of more hrs. then it will do it again. During the cooler months we were able to run it for weeks then it started this as the temps started to rise. oil temps on the gauges seem well with in range. I have tested and replaced the temp switches they seem fine. I have replaced the motor starter with the overload and the thermal units. More recently we sent the motor out to a motor shop for evaluation . They did $1300 dollars of work to it. We reinstalled it on 6/30/21
and had the same result.. Com-05 runs most of the time but back in April while I was on vacation it tripped the breaker and blew one fuse, then the week after I got back it blew one fuse (not the same fuse) it has ran fine until 6/30/21 then it tripped the breaker and blew one of the fuses. I have done an amp draw on both compressors . Readings are A Phase= 100 amps B Phase = 87 Amps and C Phase= 88 Amps. All connections seem fine. I am at a loss
We are running 240 VAC 3 phase into the building to a 400 amp I-line from there a 150 amp breaker carries power to a 200 amp disconnect. with 150 amp fuses. from there it goes to a switch box that allows me to select which compressor I want to use. Com-01 the older one will run for 5-6 hrs. then it will trip the motor overload in the cabinet. by the time I get there (5 Min) I am able to reset the overload and it will run for a couple of more hrs. then it will do it again. During the cooler months we were able to run it for weeks then it started this as the temps started to rise. oil temps on the gauges seem well with in range. I have tested and replaced the temp switches they seem fine. I have replaced the motor starter with the overload and the thermal units. More recently we sent the motor out to a motor shop for evaluation . They did $1300 dollars of work to it. We reinstalled it on 6/30/21
and had the same result.. Com-05 runs most of the time but back in April while I was on vacation it tripped the breaker and blew one fuse, then the week after I got back it blew one fuse (not the same fuse) it has ran fine until 6/30/21 then it tripped the breaker and blew one of the fuses. I have done an amp draw on both compressors . Readings are A Phase= 100 amps B Phase = 87 Amps and C Phase= 88 Amps. All connections seem fine. I am at a loss
