[Carl n Susan]

OK, now we know it is an inverter. You say the unit works on shore power. I assume the "unit" is the RV.

The basic power cord you are using for shore power should be fine. If you have a short when plugging the shore power cord into the inverter, then the short must be in the adapters you are using to convert from a 50/30 plug down to 15 amp one. I assume you have plugged a test lamp into the inverter to ensure it does work?????

The inverters I have worked with didn't have short circuit alarm. But they did have an over voltage alarm. Could this be what you are hearing? Before plugging the RV into the inverter be sure to turn off the electric hot water heater, converter and any other high amperage draw devices. If those are on they will draw much more than your inverter can supply and a load screeching alarm is the result.