Ground circuit monitor

Claim 2

In a ground monitor device the combination comprising first, second and third input terminals for coupling thereto, respectively, the high, ground and neutral conductors of an electrical supply source, said ground and neutral conductors normally being coupled to earth ground at least at said source, a relay winding connected between said high and neutral conductors, switching means having first and second switching conditions connected between said high and neutral conductors, said switching means operating to energize said relay winding when in its first switching condition and operating to deenergize the relay winding when in its second switching condition, means responsive to the voltage between said second and third input terminals for producing a first signal when said voltage differs by a predetermined magnitude from a given voltage, means coupling said switching means to the means responsive to the voltage between the second and third input terminals for operating the switching means to its second switching condition upon occurrence of said first signal, delayed operating latch means operatively coupled to said switching means for latching said switching means in its second switching condition at a fixed time delay after occurrence of said first signal, and relay switch means operable in response to energization of said relay winding.

Claim 3

The combination claimed in claim 1 and further including a high impedance conduction path coupled between said first and second terminals for limiting current flow therebetween to a value below that considered to be hazardous to a human that may come into conductive contact therewith.

Claim 4

The combination claimed in claim 2 wherein said means responsive to the voltage between said second and third input terminals has an input coupled to said second input terminal and wherein said combination further includes a second high impedance conduction path coupled between said second and third input terminals.

Claim 5

The combination claimed in claim 3 wherein said means responsive to the voltage between the second and third input terminals has an input impedance which is larger than the impedance of said high impedance conduction path between the second and third input terminals.

Claim 6

The combination claimed in claim 4 wherein said switching means is serially connected with said relay winding between said first and third input terminals, and further including means for providing only unidirectional current flow through said relay winding and switching means and through said two high impedance conduction paths.

Claim 7

The combination claimed in claim 5 wherein said switching means comprises a three electrode controlled conduction device having a control electrode and second and third electrodes, said second and third electrodes being connected for a serial conduction path with said relay winding.

Claim 8

The combination claimed in claim 6 wherein said delayed operating latch means comprises a second three electrode controlled conduction device having a control electrode and second and third electrodes, one of said second and third electrodes of the second controlled conduction device being coupled to the control electrode of the first controlled conduction device and the other one of the second and third electrode of the second controlled conduction device being coupled to the like terminal of the first controlled conduction device, and signal delay means for coupling the control electrode of the second controlled conduction device to a junction between the relay winding and said first controlled conduction device.

Claim 9

Electrical monitoring means for disconnecting an electrical utilization apparatus from electrical supply conductors upon occurrence of an undesired electrical condition comprising, first, second and third input terminals for coupling thereto, respectively, high, ground and neutral conductors of an electrical supply source, said ground and neutral conductors normally being coupled to earth ground at least at said source, switch means for selectively connecting at least said high conductor to an electrical utilization apparatus, means including high impedance means for establishing a high impedance unidirectional current path between said first and second input terminals, said high impedance means being proportioned to limit current flow through said path to a magnitude less than that considered to be potentially hazardous to a human, monitoring means for monitoring the voltage between said second and third input terminals and for producing a first signal when said voltage exceeds a predetermined magnitude, means coupled to the monitoring means for operating said switch means to connect said high conductor to said utilization apparatus in the absence of said first signal and substantially immediately responsive to said first signal to operate said switch means to disconnect said high conductor from the utilization apparatus, and delayed operating means operatively coupled to said last named means and operable only after a given time delay following said first signal for disabling said last named means from further operating said switching means.

Claim 10

Electrical monitoring means for disconnecting an electrical utilization apparatus from electrical supply conductors upon occurrence of an undesired electrical condition comprising, first, second and third input terminals for coupling thereto, respectively, high, ground and neutral conductors of an electrical supply source, said ground and neutral conductors normally being coupled to earth ground at least at said source, switch means for selectively connecting at least said high conductor to an electrical utilization apparatus, means including high impedance means for establishing a high impedance unidirectional current path between said first and second input terminals, said high impedance means being proportioned to limit current flow through said path to a magnitude less than that considered to be potentially hazardous to a human, monitoring means for monitoring the voltage between said second and third input terminals and for producing a first signal when said voltage exceeds a predetermined magnitude, means coupled to the monitoring means for operating said switch means to connect said high conductor to said utilization apparatus in the absence of said first signal and substantially immediately responsive to said first signal to operate said switch means to disconnect said high conductor from the utilization apparatus, and delayed operating means operatively coupled to said last named means and operable only after a given time delay following said first signal for disabling said last named means from further operating said switching means.

Claim 11

The combination claimed in claim 8 wherein said delayed operating means is so constructed and so operatively connected to said means coupled to the monitoring means to be rendered inoperable and incapable of disabling said means coupled to the monitoring means in the event said means coupled to the monitoring means first is operated to connect the high conductor to the utilization apparatus.

Claim 12

The combination claimed in claim 8 wherein said means coupled to the monitoring means for operating said switch means comprises: a relay coil and a semiconductor switching device series connected between said first and third input terminals, said semiconductor device having a control electrode coupled to receive said first signal and also coupled through impedance means to said first terminal and being rendered nonconductive upon occurrence of said first signal, said switch means being operable in response to energization and deenergization of said coil.

Claim 13

The combination claimed in claim 10 wherein said delayed operating means comprises: a second semiconductor device having a control electrode coupled to a junction between said relay coil and said semiconductor switching device, and signal delay means for coupling the control electrode of the second semiconductor device to said junction, said second semiconductor device being constructed and connected to provide a conduction path from the control electrode of the semiconductor switching device to the third input terminal only at a given time after the first occurrence of said first signal, thereby to hold said semiconductor switching device in a nonconducting state.

Claim 14

in a ground monitor device the combination comprising: first, second and third input terminals for respectively coupling thereto high, ground and neutral conductors of an electrical supply source, said ground and neutral conductors normally being connected to earth ground at least at said source, means for providing a first unidirectional current path between said first and third input terminals, a relay winding connected in said first unidirectional current path between said first and third input terminals. a first controllable conduction device having a control electrode and second and third electrodes connected for serial current conduction through said winding and said controllable conduction device, means including first high impedance means for providing a first high impedance unidirectional current conduction path between said first and second input terminals, means including second high impedance means for providing a second high impedance unidirectional current conduction path between said second and third input terminals, said two impedance means being proportioned to limit current in the respective high impedance conduction paths to values less than that considered potentially hazardous to a human who may come into conductive contact therewith, means coupled to said second high impedance conduction path for monitoring a voltage difference between said second and third input terminals and for producing a first signal when said voltage difference reaches a predetermined magnitude, means for coupling said first signal to the control electrode of the first controllable conduction device to cause conduction to substantially cease therethrough, thereby to deenergize the relay coil, relay switch means for providing switching operations in response to energization and deenergization of said relay winding, a second controllable conduction device having a control electrode and second and third electrodes, signal delay means for coupling the control electrode of the second controllable conduction device to a junction between said winding and said first controllable conduction device, means for coupling the second and third electrodes of the second controllable conduction device between the control electrode of the first controllable conduction device and the third input terminal, means for coupling the control electrode of said first controllable conduction device to said first input terminal by way of said first unidirectional current path, whereby a conduction path from the control electrode of the first controllable conduction device through the second controllable conduction device is provided at a predetermined time after occurrence of said first signal, thereby to latch said first controllable conduction device in its nonconducting condition even though said first signal should terminate.

Claim 15

in a ground monitor device the combination comprising: first, second and third input terminals for respectively coupling thereto high, ground and neutral conductors of an electrical supply source, said ground and neutral conductors normally being connected to earth ground at least at said source, means for providing a first unidirectional current path between said first and third input terminals, a relay winding connected in said first unidirectional current path between said first and third input terminals. a first controllable conduction device having a control electrode and second and third electrodes connected for serial current conduction through said winding and said controllable conduction device, means including first high impedance means for providing a first high impedance unidirectional current conduction path between said first and second input terminals, means including second high impedance means for providing a second high impedance unidirectional current conduction path between said second and third input terminals, said two impedance means being proportioned to limit current in the respective high impedance conduction paths to values less than that considered potentially hazardous to a human who may come into conductive contact therewith, means coupled to said second high impedance conduction path for monitoring a voltage difference between said second and third input terminals and for producing a first signal when said voltage difference reaches a predetermined magnitude, means for coupling said first signal to the control electrode of the first controllable conduction device to cause conduction to substantially cease therethrough, thereby to deenergize the relay coil, relay switch means for providing switching operations in response to energization and deenergization of said relay winding, a second controllable conduction device having a control electrode and second and third electrodes, signal delay means for coupling the control electrode of the second controllable conduction device to a junction between said winding and said first controllable conduction device, means for coupling the second and third electrodes of the second controllable conduction device between the control electrode of the first controllable conduction device and the third input terminal, means for coupling the control electrode of said first controllable conduction device to said first input terminal by way of said first unidirectional current path, whereby a conduction path from the control electrode of the first controllable conduction device through the second controllable conduction device is provided at a predetermined time after occurrence of said first signal, thereby to latch said first controllable conduction device in its nonconducting condition even though said first signal should terminate.

Claim 16

The combination claimed in claim 12 wherein said signal delay means comprises a resistance-capacitance time delay circuit for preventing the second controllable conduction device from initially conducting prior to initial conduction of the first controllable conduction device in the absence of said first signal.

Claim 17

The combination claimed in claim 12 wherein said means for monitoring the voltage difference between said second and third input terminals is a semiconductor FET device having an input impedance higher than the respective high impedance unidirectional current conduction paths between the first and second and between the second and third input terminals.

Claim 18

The combination claimed in claim 14 wherein said relay switch means include at least one pair of contacts and a movable arm movable between said contacts in response to energization and deenergization of said relay winding, and further including: means for coupling said high conductor to said movable arm, a warning device coupled to one of said contacts of the relay switch means, and an electrical utilization apparatus coupled to the other contact of the relay switch means.

Claim 19

The combination claimed in claim 15 and including: a ground conductor connecting said second input terminal to a ground terminal on said utilization apparatus, said ground terminal being connected to the ground conductor of said electrical supply system.

Claim 20

An electrical system monitoring device comprising: first, second and third input terminals for coupling thereto, respectively, high, ground and neutral conductors of an electrical system, said ground and neutral conductors normally being coupled to earth ground at least at the source of said system, a relay coil coupled between said first and third input terminals, a first three electrode transistor having its collector-emitter conduction path series connected between said coil and third input terminal, rectifier means coupled between said first terminal and said coil for providing a unidirectional current path therethrough, resistance means coupled between said rectifier means and second input terminal for providing a first high impedance unidirectional current conduction path therebetween, second rectifier means and resistor means coupled between said second and third input terminals for providing a second high impedance unidirectional conduction path therebetween, said first and second high impedance paths each limiting current therethrough to respective values less than that considered potentially hazardous to a human, and FET semiconductor device having one of its drain or source electrodes connected through resistor means to a junction between said rectifier means and coil and the other one of its drain or source electrodes coupled to said third terminal, said FET device having its gate electrode coupled to said second high impedance unidirectional conduction path for monitoring the voltage difference between said second and third input terminals, said FET device having an input impedance greater than that of the second high impedance path, and producing an output signal when the voltage difference between said second and third terminals exceeds a given magnitude, means for coupling an output signal from said FET device to the base electrode of said first transistor to turn it off upon occurrence of said output signal, thereby to deenergize said coil, a second three terminal transistor having its collector-emitter conduction path coupled between the base of said first transistor and said third input terminal and having its base electrode coupled to a junction between said coil and first transistor, signal delay means for coupling the base of said second transistor to the junction between the coil and first transistor, a resistor coupled between the base of said first transistor and a junction between said first rectifier means and coil, a diode connected in reverse polarity across said coil, relay switch means operable in response to the energization and deenergization of said coil, and means for coupling at least said high conductor to said relay switch means.

Claim 21

An electrical system monitoring device comprising: first, second and third input terminals for coupling thereto, respectively, high, ground and neutral conductors of an electrical system, said ground and neutral conductors normally being coupled to earth ground at least at the source of said system, a relay coil coupled between said first and third input terminals, a first three electrode transistor having its collector-emitter conduction path series connected between said coil and third input terminal, rectifier means coupled between said first terminal and said coil for providing a unidirectional current path therethrough, resistance means coupled between said rectifier means and second input terminal for providing a first high impedance unidirectional current conduction path therebetween, second rectifier means and resistor means coupled between said second and third input terminals for providing a second high impedance unidirectional conduction path therebetween, said first and second high impedance paths each limiting current therethrough to respective values less than that considered potentially hazardous to a human, and FET semiconductor device having one of its drain or source electrodes connected through resistor means to a junction between said rectifier means and coil and the other one of its drain or source electrodes coupled to said third terminal, said FET device having its gate electrode coupled to said second high impedance unidirectional conduction path for monitoring the voltage difference between said second and third input terminals, said FET device having an input impedance greater than that of the second high impedance path, and producing an output signal when the voltage difference between said second and third terminals exceeds a given magnitude, means for coupling an output signal from said FET device to the base electrode of said first transistor to turn it off upon occurrence of said output signal, thereby to deenergize said coil, a second three terminal transistor having its collector-emitter conduction path coupled between the base of said first transistor and said third input terminal and having its base electrode coupled to a junction between said coil and first transistor, signal delay means for coupling the base of said second transistor to the junction between the coil and first transistor, a resistor coupled between the base of said first transistor and a junction between said first rectifier means and coil, a diode connected in reverse polarity across said coil, relay switch means operable in response to the energization and deenergization of said coil, and means for coupling at least said high conductor to said relay switch means.

Claim 22

The combination claimed in claim 17 and further including: an additional rectifier coupled to said third terminal for conducting current flowing through said coil and first transistor.