Single phase to three phase converter

  • US 5,969,957 A
  • Filed: 02/04/1998
  • Issued: 10/19/1999
  • Est. Priority Date: 02/04/1998
  • Status: Expired due to Term
First Claim
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1. An apparatus for converting a single phase AC input signal to a three phase AC output signal, comprising:

  • (a) first and second single phase AC input terminals connected to first and second input lines, respectively;

    (b) three output lines connectable to a three phase load, a first of the output lines connected to the first input line and a second of the output lines connected to the second input line;

    (c) an inverter circuit connected to the input lines to receive single phase AC power therefrom and having an output node connected to a third of the output lines, the inverter circuit responsive to inverter control signals to provide an AC output signal at the inverter circuit output node;

    (d) a bi-directional switch responsive to bi-directional switch control signals connected in series with the first input line between the first input terminal and both the first output line and the inverter circuit; and

    (e) controller means for providing the inverter control signals to the inverter circuit to control the inverter circuit to provide the AC output signal at the output node of the inverter to provide a three phase AC waveform signal on the three output lines and for providing the bi-directional switch control signals to phase control the bi-directional switch during start-up of a load to adjust the amplitude of the three phase AC waveform signal to ramp up the current provided on the output lines to soft start the load and to limit inrush current to the apparatus.

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