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Method and apparatus for sensing a ground fault in a motor control system

  • US 5,386,183 A
  • Filed: 01/18/1994
  • Issued: 01/31/1995
  • Est. Priority Date: 01/03/1990
  • Status: Expired due to Term
First Claim
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1. A method for sensing a ground fault in a motor control system including a motor coupled to at least two conductors, the method comprising the steps of:

  • generating a first unrectified signal indicative of the current level in a first conductor;

    generating a second unrectified signal indicative of the current level in a second conductor;

    summing the first and second unrectified signals to generate an unrectified sum signal indicative of the sum of the current levels;

    rectifying the sum signal to produce a rectified sum signal and data representative thereof;

    comparing the data to a predetermined limit; and

    generating indicia of a ground fault in response to the data exceeding the predetermined limit for more than a predetermined time period.

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