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Soft switched three phase inverter with staggered resonant recovery system

  • US 5,576,943 A
  • Filed: 05/22/1995
  • Issued: 11/19/1996
  • Est. Priority Date: 05/22/1995
  • Status: Expired due to Term
First Claim
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1. A resonant recovery circuit for returning semiconductor switching device loss energy from a snubber circuit of a DC to AC inverter to a DC voltage supply potential powering the semiconductor switching device, said recovery circuit comprising:

  • a recovery circuit per phase signal output of a DC to AC inverter including;

    a first controllable semiconductor recovery switch means having a conductive state and non-conductive state;

    a second controllable semiconductor recovery switch means having a conductive state and non-conductive state;

    a split DC voltage supply means for supplying a positive DC voltage bus and a negative DC voltage bus relative to the positive DC voltage bus;

    said first and second recovery switch means being connected in a series circuit arrangement between said positive and negative DC voltage buses, respectively and defining a junction at the connection between said first and second recovery switches;

    a capacitor divider circuit means connected between said positive and negative DC voltage buses, respectively, said capacitor divider circuit means further comprising a first and second capacitor in a series circuit arrangement and defining a junction at the connection between said first and second capacitor;

    a recovery inductor connected between said recovery switches junction and said capacitors junction;

    first and second sets of diode means where each set of diode means is configured to return energy to the DC bus line from a power pole of a DC to AC inverter, the actuation of the power poles being staggered from one another to efficiently recover energy generated by switching losses within each power pole;

    each set of diode means per power pole comprising a first recovery diode means coupled between a first snubber capacitor of a first snubber circuit associated with a first semiconductor power pole switching device and said first recovery switch means for discharging said first snubber capacitor through said recovery inductor when said first recovery switch means is made conductive by switch control circuitry which is timed so that a first pulse of current is delivered to the junction of said first and second switching capacitors to be returned to the DC voltage buses during a positive half cycle of the AC output of the inverter;

    a second recovery diode means coupled between a second snubber capacitor of a second snubber circuit associated with a second semiconductor power pole switching device and said second recovery switch means for discharging said second snubber capacitor through said recovery inductor when said second recovery switch means is made conductive by switch control circuitry which is timed so that a second pulse of current is delivered to the junction of said first and second capacitors to be returned to the DC voltage buses during a negative half cycle of the AC output of the inverter, said first recovery switch means being conductive when said secondary recovery switch means is non-conductive and said first recovery switch means being non-conductive when said second recovery switch means is conductive.

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