Patent ID: 8643985

Claim:
Apparatus for selectively coupling and de-coupling first and second monopolar DC sources to and from an earth ground and positive and negative terminals of a monopolar load, comprising: a bipolar DC source that includes said first and second monopolar DC sources each having positive and negative terminals, with the positive terminal of said first monopolar DC source and the negative terminal of said second monopolar DC source connected to a DC-to-AC converter, the negative terminal of said first monopolar DC source and the positive terminal of said second monopolar DC source being connected to each other at a common connection point that is also connected to earth ground, with the stated polarities referenced to said earth ground, and a single network of frequency-selective parallel-connected RLC devices connected between said common connection point and said earth ground, said network having a DC impedance that is lower than the AC impedance of said network at a preselected frequency.