Sundstrand Corporation

Joseph S Breit

William M Spencer

A three phase inverter (10) in accordance with the invention includes a first phase inverter (12) producing a first phase AC output voltage from a DC power supply; a second phase inverter (14) producing a second phase AC output voltage which is displaced nominally 120.degree. from the first phase from the DC power supply; and a vector adding circuit (32), responsive to the first and second phases, for vectorially adding voltages proportional to output voltages from the first and second phases to produce a resultant voltage which is inverted to produce a third phase having an output voltage which is displaced nominally 120.degree. from the output voltages produced by the first and second phases.

DC to AC inverter and method for producing three phases from two input

A contactor (12) for controlling connection of a DC power supply to an electrical load (14) in includes a series circuit (19) disposed between a nonground DC potential and a load having first (20) and second (22) relays each having a pair of contacts (26), the first relay and the second relay having a conducting state when the pair of contacts are closed and a non-conducting state when the pair of contacts are open which control current flow between the DC power supply and the load with the states being controlled by control signals applied to the relays; a semiconductor switch (24) having a conductive state controlled by a control signal to turn on the semiconductor switch to connect the semiconductor switch in parallel with the contacts of the first relay and a non-conductive state controlled by a control signal to turn off the semiconductor switch to disconnect the terminals of the semiconductor switch; a fault sensor (50) coupled to the load for generating a signal in response to the load drawing current exceeding a threshold to cause the second relay to open to disconnect the load from the power supply; and a control signal generator (28) for generating the control signals of the switches.

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Rockford, IL, United States of America

Joseph S Breit