Motors tripping incoming power

[Gaspipeliner]

I have two airdyne air compressors on a lead ane lag system however, when the second air compressor turns on it kills the incoming power breaker. Each motor is 56HP and the incoming power is on a 250 Amp breaker. I have considered that it might be to much load on the system but when I checked the load on the main breaker at most I was pulling 160 Amps. Do I need to consider a larger sevice for the Station?

 

[augie47]

What voltage ?
Does each compressor have individual GFSC protection such as a fuse or breaker.. ?.

It's possible your breaker is undersized and this info will help determine that,

 

[ptonsparky]

56 HP is a little odd. 60 hp? 50HP? what voltage?

 

[Jraef]

56 HP is a little odd. 60 hp? 50HP? what voltage?

Probably one of those "develops 56HP" things they do when marketing compressors, but in reality it's a 30HP motor...

If the problem is always the same compressor, it might be that the unload valve is sticking a little. If it's not fully open when you energize the starter, it will cause the compressor motor to go to almost locked rotor amps. If you have an inexpensive meter, it may be hapening too fast for the meter to see it, but fast enough for the breaker's magnetic trips to react to it. It could also just be that the motor on that particular compressor has a higher starting current than the other one and your mag trip setting on that 250A breaker is too low for it.

 

[kwired]

Probably one of those "develops 56HP" things they do when marketing compressors, but in reality it's a 30HP motor...

If the problem is always the same compressor, it might be that the unload valve is sticking a little. If it's not fully open when you energize the starter, it will cause the compressor motor to go to almost locked rotor amps. If you have an inexpensive meter, it may be hapening too fast for the meter to see it, but fast enough for the breaker's magnetic trips to react to it. It could also just be that the motor on that particular compressor has a higher starting current than the other one and your mag trip setting on that 250A breaker is too low for it.

That said, 250 amps is getting into range where it is more common for the breaker to possibly have a magnetic trip adjustment.

Outside of sticking unload valve, this is likely the issue. Soft start controller is also a possible solution to the problem if that is the case.

 

[hillbilly1]

That said, 250 amps is getting into range where it is more common for the breaker to possibly have a magnetic trip adjustment.

Outside of sticking unload valve, this is likely the issue. Soft start controller is also a possible solution to the problem if that is the case.

I agree, it's probably at factory default of "minimum".

 

[brian john]

sS the main circvuit breaker over curent protection adjustable, if so it is very typical for the installing electricians to DO NOTHING with the settings.

What size main?
What are the settings?