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Electric power converter

  • US 4,926,306 A
  • Filed: 08/03/1989
  • Issued: 05/15/1990
  • Est. Priority Date: 08/12/1988
  • Status: Expired due to Fees
First Claim
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1. An electric power converter having:

  • a bridge circuit of plural phases, which includes plural rectifying branches corresponding to the respective phases, which are coupled in parallel across dc terminals of the bridge circuit, wherein each of the rectifying branches comprises;

    a first arm and a second arm, both including switching elements, which are connected in series with each other, in which a junction of the series-connected arms is coupled to one of ac terminals of the bridge circuit;

    a free-wheel diode coupled in reverse parallel with every switching element of said first and second arms; and

    a phase snubber circuit provided with a series connection of first and second diodes coupled across the series-connected arms through a first capacitor, in which a junction of the first and second diodes is coupled to the junction of the series-connected arms through a second capacitor and a junction of the first capacitor and the series-connected first and second diodes is coupled to one of the dc terminals through a discharge path, through which charge stored in the first capacitor is discharged,characterized in thatthe respective arms of each rectifying branch include plural switching elements connected in series, and each of the switching elements is provided with an individual snubber circuit including a third capacitor being charged during turn-off of a corresponding switching element and a resistor for consuming charge discharged from the third capacitor during turn-on of the corresponding switching element, in which the first capacitor has capacitance much larger than the second capacitor, which has capacitance much larger than the third capacitor.

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