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Solid state electric power usage meter and method for determining power usage

  • US 5,391,983 A
  • Filed: 10/08/1991
  • Issued: 02/21/1995
  • Est. Priority Date: 10/08/1991
  • Status: Expired due to Fees
First Claim
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1. An electric power usage meter for determining electric power usage by a load attached to an electric power network, the power network having a network frequency and voltage and current waveforms, the power usage meter comprising:

  • first means coupled to each phase of the electric power network for sensing current in each phase;

    second means coupled to each phase of the electric power network for detecting the voltage level on each phase;

    third means coupled to the first and second means receiving signals from the first means related to the current in each phase and signals from the second means related to the voltage on each phase, said means comprising means for periodically sampling said current and voltage related signals at predetermined times at a frequency which is non-synchronous with the network frequency such that samples defining a cycle of each of the current and voltage related signals are taken over a plurality of cycles of the network waveforms and are not made at the same points on a plurality of successive cycles of the network waveforms of the respective current and voltage related signals and for converting said samples to digital signals representing said current and voltage levels at the predetermined times;

    processor means for calculating instantaneous values of power at the predetermined times from the digital signals; and

    means for accumulating said instantaneous values so as to form a value representative of electrical power usage by the load attached to the network.

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