They say there are no such things as dumb questions.. so here goes...
If you are around this compressor, do you know if the overloads trip when starting up with the tank Empty?
Or does it trip when starting up when the tank is full, and the pressure switch just closed at the cut-in point?
Or both?
It's possible that the pressure relief valve is not venting properly (when the motor/pump cycle off) and when starting up with the tank already pressurized the piston is fighting hard to get those first few strokes in against some heavy head pressure.
If there was a compressor company looking over this problem, I have to assume that they'd find that problem out in a heartbeat.
#10 copper and 200 feet and 30 amps shows ~ 5.7% VD. Not super crazy, but you are getting down to ~196 VAC (if starting from 208). And if the motor is at all undersized, it could be struggling at startup some. Measuring start-up voltage available at the motor would be a good data point - especially if summer time voltages in your area are on the low side. Our commercial shop could typically be 202 VAC in the summer daytime.
You could get a reasonable feel for an undersized motor by watching an amp clamp meter and tracking motor current as the tank pressure heads towards the cut-out point. Comparing the max current seen against the motor nameplate might give you a clue.
