Ground fault detector
First Claim
1. A ground fault detector for connection between an electrical power source and a load, said source and said load each having a ground connection, a neutral terminal, and at least one other terminal, said detector comprising:
- circuit interrupting means comprising a solenoid device having a primary actuating winding and at least one secondary winding;
a differential transformer having at least two primary windings and a secondary winding, said transformer developing a voltage across the secondary winding thereof corresponding to the difference between the currents flowing through the primary windings thereof;
amplifier means coupled between the secondary winding of said differential transformer and said circuit interrupting means for supplying an actuating voltage to the primary winding of said solenoid device when the voltage across said differential transformer secondary winding exceeds a predetermined value;
means for connecting one primary winding of said differential transformer and the secondary winding of said solenoid device in series between the neutral terminal of said power source and the neutral terminal of said load;
means for connecting another primary winding of said differential transformer between the other terminal of said power source and the other terminal of said load; and
means for supplying an exciting voltage to the primary actuating winding of said solenoid device, said exciting voltage being substantially less than the voltage across said primary actuating winding required to actuate said circuit interrupting means.
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Accused Products
Abstract
A ground fault detector for protecting an electrical power system against ground leakage currents. The detector is of the differential transformer type, in which the primary windings of the transformer are connected in series with the hot and neutral lines of the power system, any unbalance in the currents flowing through these lines being detected by sensing the unbalance voltage induced in the secondary winding of the transformer. The secondary voltage is amplified and employed to actuate a solenoid which trips the system circuit breaker in response to unbalance in line and neutral currents due to the flow of ground leakage current. A secondary winding on the solenoid is connected in the neutral line to cause the detector to operate in response to a neutral to ground fault, which might otherwise go undetected.
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Citations
10 Claims
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1. A ground fault detector for connection between an electrical power source and a load, said source and said load each having a ground connection, a neutral terminal, and at least one other terminal, said detector comprising:
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circuit interrupting means comprising a solenoid device having a primary actuating winding and at least one secondary winding; a differential transformer having at least two primary windings and a secondary winding, said transformer developing a voltage across the secondary winding thereof corresponding to the difference between the currents flowing through the primary windings thereof; amplifier means coupled between the secondary winding of said differential transformer and said circuit interrupting means for supplying an actuating voltage to the primary winding of said solenoid device when the voltage across said differential transformer secondary winding exceeds a predetermined value; means for connecting one primary winding of said differential transformer and the secondary winding of said solenoid device in series between the neutral terminal of said power source and the neutral terminal of said load; means for connecting another primary winding of said differential transformer between the other terminal of said power source and the other terminal of said load; and means for supplying an exciting voltage to the primary actuating winding of said solenoid device, said exciting voltage being substantially less than the voltage across said primary actuating winding required to actuate said circuit interrupting means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification