Patent ID: 8729869

Claim:
An apparatus, comprising: a mobile electric power generation system including a mobile power source with a generator, an external power interface to connect to an external electrical power source when the electric power generation system is stationary, an AC electric power distribution bus, and a power switch device to selectively provide AC electric power on the power distribution bus from one of the power source and the external power interface, the power switch including: a first normally open contactor between the external power interface and the power distribution bus, a normally closed switch, a first normally closed contactor, and a first contactor state control; a second normally open contactor between the mobile power source and the power distribution bus, a normally open switch, a second normally closed contactor, and a second contactor state control; and control circuitry to selectively switch each of an external power circuit and a mobile power circuit between an opened state and a closed state, the external power circuit connecting the normally closed switch, the first contactor control and the second normally closed contactor in series, the generated power circuit connecting the normally open switch, the second contactor state control and the first normally closed contactor in series.