probably trips due to some small current on the ground wire when you plug in. If you bypass the ground breaker you will probably solve the problem.. I have had the same problem when using a transformer to plug into 220 V. The neutral and the ground must be at the exact same potential to prevent tripping.

To bypass the ground portion of the circuit breaker join the green wires together or jumper across that segment of the breaker. Of course make sure he power is unplugged when working with line voltages.

I talked to Bass, the people that made my panel. They said that my three pole main breaker (one toggle, three breakers tied together) was no longer available.