A/C on shore power trips breaker after 30 minustes

From what I understand the ohms law is causing the voltage to lower because of the distance from the coach to the wall socket and then the fact that it is only 120 v. This load raises the amps and the A/C pulls more than 20 amps tripping the breaker. The inhouse generator eliminates all that load and provides more than enough amperage to support the A/C.