Patent ID: 7916507

Claim:
A high voltage inverter for converting DC input power to three or more AC output phases with individual current control of each output phase, comprising: a) each AC output phase having an AC input phase circuit comprising: i) first and second cold cathode field emission controllable electron tubes of triode, tetrode or pentode structure; ii) a primary transformer winding having a first end, a second end, and a center tap; iii) the center tap being connected to a DC potential in excess of 20 KV; iv) the first electron tube being serially connected between the first end of the primary winding and the ground, and the second electron tube being serially connected between the second end of the primary winding and the ground; and v) the conduction state of each electron tube being controlled to convert from DC power at a potential in excess of 20 KV to AC power via said primary transformer winding; the first and second electron tubes alternately conducting so as to alternately bring the first end of the primary winding approximately to the potential of the ground and then bring the second end of the primary winding approximately to the potential of the ground; b) for each AC input phase primary winding, a respective secondary winding of an associated AC output phase coupled thereto; each primary winding and associated secondary winding forming a multi-phase transformer; c) means for adjusting the current in each individual phase, comprising: i) means for determining voltage, current and phase angle in each AC output phase, and ii) current-control means, responsive to said means for determining, for controlling the current level of each output phase in a continuously variable manner; the current-control means including a third cold cathode field emission controllable electron tube serially connected between the first electron tube and the primary winding, and a fourth cold cathode field emission controllable electron tube serially connected between the second electron tube and the primary winding.