I have an 80gal Ingersoll Rand compressor.  The motor kicks on for a few seconds then trips the breaker.  Just had the motor rebuilt with all new capacitors.  Was doing the same thing before it was rebuilt.  Motor shop guys said that essentially it is better than new.  Fuses are good.  Power coming in is good.  Any help would be greatly appreciated.

Well, if your power supply is high enough to supply the peak power of the motor startup, and the motor is supposed to be good, and the thing that is being a problem is the breaker...
By process of elimination, it sounds like it might be time to check the breaker?  They can go bad over time and need to be replaced occasionally.

 

Have you checked the amp draw? It could be the compressor not the motor.

Assuming that the rebuild is good,  I would recheck the capacitors.

Next look at the compressor check valve.

Corroded receptacle, Loose wire? 2nd checking amp draw and weak breaker

Check valve or unloader if motor is known to be good. If it fills with no pressure in the tank then won't cycle to replenish it's not letting pressure off the head and it's the unloader or relief valve is my guess.

You did empty (drain) the tank didn't you?

Stay safe

Yep.

What are the voltage and amperage  requirements on the motor tag?   Next tell us what size breaker and what gauge wire you have the motor wired with and how far away from the breaker are you.

This is what needs to be known before anything else.

I just had the service and panel upgraded last September. It worked fine up until February. It's a double 40 breaker. I don't know  the gauge wire. I had a well known electrical company come and do the work. I will also mention this is in a small commercial building.  Compressor is 20 ft from the panel.

Motor loads have their own special section in the NEC.
Article 430.
Conductor size is 125% ofthe motors full load operating current.
The number on the motor is NOT used.
Article 430 has its own required table for foll load currents.

The breaker can then be increased to allow the motor to start.

I would at least open the compressor to tank line and see if the motor will start up with almost no load.

Pics just showed up.
7.5 HP, 240 V is 40 amp full load.
Breaker is then 125% of that or 50 amps.
Wires are #6

An inverse-time (thermal magnetic) breaker can be increased up to 250% to allow starting (125 amps).
If it will not start on a 50 amp go to the next available size breaker.

The 'trick' to all this is that the motor has its own thermal overload protection built in (or in the controller you have).
It will not draw enough to damage itself without overheating and turning off.
The breaker is only for short circuit protection of the feeder.

The "CODE A" indicates it will pull up to 3.14 kV-A per horsepower on start-up. Up to 98 amps.
And that is a low start-up rating per HP.

According to brickeye's post your wiring is not  big enough. Here is what I would do first change out the breaker for a new double pole 40 and see if that helps. If it does you then need to upgrade your wiring to meet the info that brickeye posted because what is happing is you are putting such a load on a 40 amp breaker that it has gotten weak. If a new breaker doesn't help then you have another problem with either the motor or a bad Unloader valve.

Thanks everyone. I'll try the new breaker and go from there. I have 2 of the same compressors side by side with the same wire and set up. So I'm going to swap mains coming in with the one that works and see if the jacked up one starts working. Thanks again

After breakers trip enough times the contact are damaged and cause heat buildup in the breaker.

This

When a compressor reaches max pressure and the motor shuts off, you should hear a HISS. If you don't hear that, the compressor will starting under load the next cycle.

With the space being a small commercial space I would check to see if you have 3 phase power.

With the motor being a 7.5 HP that is pretty big for single phase. Anything over 1HP, I would run on 3 phase if it was available.

Single phase motor just don't have the starting torque 3 phase ones have


Also 40amp breaker seems a little small consider the rated amps for the motor is almost 35 amps. Startup amps on that motor is most likely over 50 amps. I would look at a bigger breaker, already mentioned previously

NEC does NOT use motor plate for current.

GarageJournal.com-they are always discussing compressors and electrical requirements