OP
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So for anyone who has been following on Tuesday (7/6/21) I got a call at home and was told that there was a power outage at work for 2.5- 3 hrs but the air compressor would not come on and had no display. I advised the lead man to check the breaker in the I-Line that controls the power to our compressor shed. When he returned to the phone he said that was it and air pressure was coming up. Wednesday I was out, so on Thursday I was told that they had replaced a transformer about 2 blocks from here. We have been told that we are the last business in this grid. so anything that happens upstream is going to affect us. Today 6/9/21 I went do some more testing under the direction of one of our fellow members. This is the results that I have now. Voltage coming into the disconnect in the compressor shed A-B Phase 234 VAC, B-C Phase 236 VAC, C-A Phase 237 VAC A - Grnd = 205 VAC , B - Grnd = 118 VAC, C- Grnd = 116 VAC Amp draw A - Phase = 110A,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
B Phase = 112A, C Phase = 114 A Sorry for the long post but I want to make sure you have as many details as I can give you .