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Two-level protection for uninterrupted power supply

  • US 20050105229A1
  • Filed: 11/14/2003
  • Published: 05/19/2005
  • Est. Priority Date: 11/14/2003
  • Status: Abandoned Application
First Claim
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1. A method for responding to electrical power source irregularities in an uninterruptible power supply system utilizing a rechargeable DC power supply as back up power, comprising:

  • providing an uninterruptible power supply system comprising a three phase AC source converter connectable to a three phase AC power source and a three phase AC load converter connectable to a three phase load, wherein the converters are interconnected by a DC bus;

    monitoring DC bus voltage on the DC bus;

    establishing a first DC bus voltage threshold indicative of a first power source irregularity and a second DC bus voltage threshold indicative of a second and distinct power source irregularity, wherein the first threshold is greater than the second threshold;

    comparing the DC bus voltage to the first and second thresholds;

    commuting electrical power from both the power source and from the DC power supply to the DC bus when the DC bus voltage is intermediate the first and second thresholds; and

    , conversely commuting electrical power only from the DC power supply to the DC bus when the DC bus voltage is less than the second threshold, and disabling the source converter.

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