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Thermal modeling of overcurrent trip during power loss

  • US 5,418,677 A
  • Filed: 01/19/1994
  • Issued: 05/23/1995
  • Est. Priority Date: 12/28/1990
  • Status: Expired due to Term
First Claim
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1. A circuit interrupting device comprising:

  • sensing means for sensing electric current to an electrical load served by said interrupting device, said electrical load including electrical conductors;

    interrupting means interrupting current to said load in response to a trip signal; and

    processing means comprising digital processing means responsive to said sensing means and operative when energized to generate a digital current/time value and generating said trip signal when said current/time value reaches a trip value, said digital processing means being de-energized and losing said digital current/time value when current is interrupted by said interrupting means, analog processing means maintaining an analog current/time value, means forcing said analog current/time value to track both increases and decreases in said digital current/time value when said digital processing means is energized, said analog processing means including means causing said analog current/time value to decay at a rate mimicking cooling of said load when said digital processing means is de-energized, and means initializing said digital current/time value to said analog current/time value when current to said load is reestablished and said digital processing means is again energized.

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