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Detector for monitoring the integrity of a ground connection to an electrical appliance

  • US 5,606,480 A
  • Filed: 05/08/1995
  • Issued: 02/25/1997
  • Est. Priority Date: 05/10/1994
  • Status: Expired due to Fees
First Claim
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1. A detector for monitoring the integrity of a ground connection to an electrical appliance having live and neutral terminals for feeding current to the appliance from respective live and neutral feeders of an electrical supply having a ground point for connecting to a ground terminal of the appliance, said detector comprising:

  • differential comparator circuit means for comparing a fractional voltage at the ground terminal with a fractional voltage at the neutral terminal of the appliance, and for producing a fault signal if a difference between said fractional voltages exceeds a predetermined threshold;

    wherein the differential comparator circuit means comprises;

    low voltage d.c. power supply means having a high and a low voltage rail, said low voltage rail being coupled to the ground terminal of the appliance,first voltage divider means including a pair of resistors connected in series across the high and the low voltage rails and having a common junction coupled to a first input of a comparator, andsecond voltage divider means including a pair of resistors connected in series between the high voltage rail and the neutral terminals of the appliance and having a common junction coupled to a second input of the comparator.

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