Bridge-Chopper Inverter for 400 CPS Sine Wave Power

A new d-c to a-c inverter has been developed. Sine wave power at 400 cps is provided without a 400 cps filter or 400 cps transformer. A bridge type chopper circuit, chopping at 50 KC, is used to provide the a-c power. The bridge-chopper inverter is approximately 1/3 the size and weight of present sine wave inverters used in most aircraft and space applications. The inverter is more efficient than most sine-wave inverters (85 to 90% at 100 watts 50% power factor). The sine-wave output is provided by time-ratio control. Applications of the inverter include power supplies for aircraft, space craft, ships, submarines, etc. These power supplies operate from d-c power sources such as fuel cells, solar cells, nuclear thermionic converters, batteries, etc. The new inverter is made practical by new high speed transistors that are applied with new control techniques. Fast switching in the power circuit makes the 50 KC chopping rate practical. New control techniques using tunnel diodes permit fast switching of the power transistors and permit use of insulated controls. Saturable reactors and transformers are used in the control circuit with current rise time of approximately two microseconds. The tunnel diode circuit, controlled by the saturable reactors, switches the base current of the power transistor in 0.02 micro-seconds. In turn, the chopper power transistor switches five amperes in less than 0.1 micro-second. This paper presents the bridge chopper inverter, showing its operation, and describes the control technique.