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Elevator control apparatus using parallel converters and inverters with means to control circulating current

  • US 5,460,244 A
  • Filed: 03/04/1993
  • Issued: 10/24/1995
  • Est. Priority Date: 03/06/1992
  • Status: Expired due to Term
First Claim
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1. An elevator speed control system including:

  • a plurality of converters directly connected in parallel for converting an AC voltage to a DC voltage by means of controllable devices;

    a capacitor for smoothing output voltages of the plural converters;

    a plurality of inverters connected in parallel for converting the voltages smoothed by means of said capacitor to an AC voltage whose magnitude and frequency are controllable, and for further supplying said resulting AC voltage to a hoisting induction motor;

    current detectors for detecting currents in each phase of said plural inverters; and

    a control means for calculating the sum of the currents of each inverter detected by said current detectors, the sum being designated as a zero-phase current io, and for further controlling the output voltages of said plurality of inverters so that the zero-phase current is minimized, the zero phase current being independent of the output frequency of the inverters.

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