Detector for monitoring the integrity of a ground connection to an electrical appliance
First Claim
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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Accused Products
Abstract
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 the ground terminal of the appliance. The detector comprises a differential comparator circuit for comparing a voltage at the neutral connection with a voltage at the ground terminal of the appliance and producing a fault signal if a difference therebetween exceeds a predetermined threshold. A normally closed switching device is connected in at least one of the live and neutral connections so as to be opened by a relay operatively coupled to the detector and responsive to the fault signal produced thereby.
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Citations
11 Claims
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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:
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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, and second 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification