Electronic safety system

Claim 2

An electronic safety system for detecting the presence of an electrical fault resulting in the leakage of electrical current from a load circuit to ground comprising means for coupling the load circuit to a power supply including a section of coaxial cable to minimize the affects of spurious electrical signAls, said coaxial cable having inner and outer electrical conductors, one of said electrical conductors being coupled to ground to define a path for leakage currents from the load circuit to ground, selectively energizable saturable core magnetic means electrically coupled to the power supply and inductively coupled to a portion of said section of coaxial cable intermediate the load circuit and the power supply, said saturable core magnetic means being adapted to respond to the passage of unequal currents through said inner and outer electrical conductors of said coaxial cable section, means for energizing said saturable core magnetic means in order to establish preselected magnetic fields, said preselected magnetic fields being of opposite polarity and being substantially equal during the passage of essentially equal currents through said inner and outer conductors of said coaxial cable section and being affected by the passage of unequal currents through said inner and outer conductors of said coaxial cable section in a manner systematically related to the magnitude of the leakage current, means for producing an electrical signal in response to the affect on said magnetic fields, and means for sensing the presence of said electrical signal as an indication of current leakage from the load circuit.

Claim 3

An electronic safety system in accordance with claim 1 wherein said saturable core magnetic means comprise first and second saturable core toroids electrically coupled to each other in series opposition.

Claim 4

An electronic safety system in accordance with claim 2 wherein said energizing means is adapted to establish an initial magnetic bias in said first and second saturable core toroids and to then supply an electrical pulse signal driving said first saturable core reactor into magnetic saturation in a first predetermined time interval and driving said second saturable core reactor into magnetic saturation in a second predetermined time interval, said first and second predetermined time intervals being essentially equal during the passage of substantially equal currents through said inner and outer conductors of said coaxial cable section and being unequal during the passage of unequal currents through said inner and outer conductors of said coaxial cable section so as to effect the production of an electrical signal having magnitude related to the differential time interval.

Claim 5

An electronic safety system in accordance with claim 3 wherein said energizing circuit includes means for providing half-wave rectified electrical power, a storage capacitor coupled between said means for providing half-wave rectified power and said saturable core toroids, and a selectively triggerable switch means having a control electrode, said switch means being coupled to said capacitor for effecting relatively rapid discharge thereof in order to produce a relatively high energy pulse for energizing said first and second saturable core toroids.

Claim 6

An electronic safety system in accordance with claim 4 wherein said selectively triggerable switch means comprises a silicon-controlled rectifier, and a voltage threshold device is provided coupled between said capacitor and said control electrode for triggering said silicon-controlled rectifier in response to the establishment of a preselected voltage level across said capacitor to define a discharge path for said capacitor through said silicon-controlled rectifier in order to effect the production of said high energy pulses.

Claim 7

An electronic safety system in accordance with claim 5 wherein said means for sensing the presence of said electrical signal comprises a selectively energizable switch circuit connected across the output of said first and second saturable core toroids, said selectively energizable switch circuit being adapted to be rendered conductive in response to the presence of said electrical signal.

Claim 8

An electronic safety system in accordance with claim 6 wherein a selectively operable circuit breaker Means is coupled to said switch circuit for selectively disrupting the supply of power to said load circuit in response to conduction of said switch circuit.

Claim 9

An electronic safety system in accordance with claim 7 wherein said circuit breaker means comprises a circuit breaker connected across the power supply and a normally nonconductive semiconductor switch is connected in shunt across said circuit breaker, said semiconductor switch having a control element coupled to said switch circuit for effecting conduction of said semiconductor switch in response to conduction of said switch circuit so as to establish a low-resistance conduction path across said circuit breaker in order to effect opening thereof in response to continued conduction of said semiconductor switch.

Claim 10

An electronic safety system in accordance with claim 3 wherein said energizing circuit includes means for providing full-wave rectified electrical power so as to effect magnetization of said toroids during successive half cycles of applied power, a storage capacitor coupled between said means for providing full-wave rectified power and said saturable core toroids, and a selectively triggerable switch means having a control electrode, said switch means being coupled to said capacitor for effecting relatively rapid discharge thereof in order to produce relatively high energy pulses for energizing said first and second saturable core toroids.

Claim 11

An electronic safety system in accordance with claim 9 wherein said selectively triggerable switch means comprises a silicon-controlled rectifier, and a voltage threshold device is provided coupled between said capacitor and said control electrode for triggering said silicon-controlled rectifier in response to the establishment of a preselected voltage level across said capacitor to define a discharge path for said capacitor through said silicon-controlled rectifier in order to effect the production of said high energy pulses.

Claim 12

An electronic safety system in accordance with claim 10 wherein said means for sensing the presence of said electrical signal comprises a selectively energizable switch circuit connected across the output of said first and second saturable core toroids, said selectively energizable switch circuit being adapted to be rendered conductive in response to the presence of said electrical signal.

Claim 13

An electronic safety system in accordance with claim 11 wherein a selectively operable circuit breaker means is coupled to said switch circuit for selectively disrupting the supply of power to said load circuit in response to conduction of said switch circuit.

Claim 14

An electronic safety system in accordance with claim 12 wherein said switch circuit includes a voltage sensing resistor connected across the output of said first and second saturable core toroids, another full-wave bridge rectifier network connected across said resistor, voltage threshold sensing trigger means coupled to the output of said another bridge rectifier network, and another selectively triggerable silicon-controlled rectifier having its gate coupled to said trigger means, said another silicon-controlled rectifier being adapted to be rendered conductive in response to the presence of said electrical signal.

Claim 15

An electronic safety system for selectively disrupting the supply of power to a load circuit in response to the leakage of electrical current to ground comprising means for coupling the load circuit to a source of electrical power, said coupling means including a section of coaxial cable having inner and outer conductors, one of said conductors being coupleable to ground to define a path for leakage currents from the load to ground, first and second selectively energizable saturable core transformers electrically coupled to the source of power and inductively coupled to a portion of said section of coaxial cable intermediate the load and the source of power, energizing circuit means connected between the source of power and said saturable cOre transformers for selectively energizing said first saturable core transformers in a first predetermined time interval and said second saturable core transformer in a second predetermined time interval during the passage of unequal currents through said inner and outer conductors of said coaxial cable section, means for sensing a voltage output signal developed across the output of said saturable core transformers in response to the presence of a difference between said first and said second predetermined time intervals as an indication of the flow of leakage current to ground, and selectively operable circuit breaker means coupled to said sensing means for disrupting the power being supplied to said load circuit in response to the presence of said voltage output signal.

Claim 16

An electronic safety system for selectively disrupting the supply of power to a load circuit in response to the leakage of electrical current to ground comprising means for coupling the load circuit to a source of electrical power, said coupling means including a section of coaxial cable having inner and outer conductors, one of said conductors being coupleable to ground to define a path for leakage currents from the load to ground, first and second selectively energizable saturable core transformers electrically coupled to the source of power and inductively coupled to a portion of said section of coaxial cable intermediate the load and the source of power, energizing circuit means connected between the source of power and said saturable cOre transformers for selectively energizing said first saturable core transformers in a first predetermined time interval and said second saturable core transformer in a second predetermined time interval during the passage of unequal currents through said inner and outer conductors of said coaxial cable section, means for sensing a voltage output signal developed across the output of said saturable core transformers in response to the presence of a difference between said first and said second predetermined time intervals as an indication of the flow of leakage current to ground, and selectively operable circuit breaker means coupled to said sensing means for disrupting the power being supplied to said load circuit in response to the presence of said voltage output signal.

Claim 17

An electronic safety system for selectively disrupting the supply of power to a load circuit in response to the leakage of electrical current to ground comprising means for coupling the load circuit to a source of electrical power, said coupling means including a section of coaxial cable having inner and outer electrical conductors, one of said conductors being coupleable to ground to define a path for leakage currents from the load to ground, first and second selectively energizable saturable core transformers electrically coupled to the source of power and inductively coupled to said inner and outer electrical conductors at a location intermediate the load and the source of power, an energizing circuit connected between the source of power and said first and second saturable core transformers for initially effecting magnetic biasing of each of said saturable core transformers in a first direction in a first predetermined time interval, said saturable core transformers initially being differentially magnetically biased in response to the passage of unequal electrical currents through said inner and outer conductors inductively coupled thereto, and for subsequently effecting magnetic saturation of said first and second saturable core transformers in a second opposite direction in a second predetermined time interval, said first and second time intervals being unequal in response to the initial establishment of differential magnetic biasing, whereby an electrical output signal is established across said saturable core transformers, means responsive to said electrical output signal connected across the output of said saturable core transformers for providing a trigger signal in response to said electrical output signal, and selectively operable circuit breaker means for interrupting the supply of power to the load in response to the provision of said trigger signal.

Claim 18

An electronic safety system for selectively disrupting the supply of power to a load circuit in response to the leakage of electrical current to ground comprising means for coupling the load circuit to a source of electrical power, said coupling means including a section of coaxial cable having inner and outer electrical conductors, one of said conductors being coupleable to ground to define a path for leakage currents from the load to ground, first and second selectively energizable saturable core transformers electrically coupled to the source of power and inductively coupled to said inner and outer electrical conductors at a location intermediate the load and the source of power, an energizing circuit connected between the source of power and said first and second saturable core transformers for initially effecting magnetic biasing of each of said saturable core transformers in a first direction in a first predetermined time interval, said saturable core transformers initially being differentially magnetically biased in response to the passage of unequal electrical currents through said inner and outer conductors inductively coupled thereto, and for subsequently effecting magnetic saturation of said first and second saturable core transformers in a second opposite direction in a second predetermined time interval, said first and second time intervals being unequal in response to the initial establishment of differential magnetic biasing, whereby an electrical output signal is established across said saturable core transformers, means responsive to said electrical output signal connected across the output of said saturable core transformers for providing a trigger signal in response to said electrical output signal, and selectively operable circuit breaker means for interrupting the supply of power to the load in response to the provision of said trigger signal.

Claim 19

An electronic safety system in accordance with claim 15 wherein said first and second saturable core transformers include first and second toroid cores respectively each having a primary winding and a secondary winding, said primary windings being electrically coupled to said energizing circuit, said secondary windings being electrically connected to said means responsive to said electrical output signal, and said inner and outer conductors of said coaxial cable section pass generally centrally through said toroids inductively coupled thereto and adapted to affect the magnetization thereof.

Claim 20

An electronic safety circuit in accordance with claim 16 wherein said energizing circuit includes a means for supplying rectified AC power, a capacitor connected between said means for supplied rectified AC power and said primary windings of said toroids, means coupled to said capacitor to assure the storage of a preselected voltage thereacross, a selectively energizable switch means having a control electrode, said switch means being coupled to said capacitor, and a voltage threshold sensing device coupled to said control electrode and to said capacitor to effect energization of said switch means in response to the establishment of said preselected voltage level across said capacitor to define a dischargE path for said capacitor through said switch means, whereby said toroids are initially magnetically biased in said first direction during nonconduction of said switch means and abruptly driven into magnetic saturation in said second direction in response to energization of said switch means.

Claim 21

An electronic safety system in accordance with claim 17 wherein said switch means comprises a first silicon controlled rectifier, said means responsive to said electrical output signal comprises a second silicon-controlled rectifier having its gate-cathode circuit coupled across said secondary windings, whereby the establishment of said electrical output signal across said secondary windings is effective to energize said second silicon-controlled rectifier to provide said trigger signal, and said selectively operable circuit breaker means includes a selectively energizable relay coil adapted to be energized by said trigger signals and a pair of relay contacts operatively connected to said relay coil, said relay contacts being connected between the source of power and the load for disrupting the supply of power to the load in response to energization of said relay coil.

Claim 22

An electronic safety system in accordance with claim 17 wherein said switch means comprises a first silicon-controlled rectifier, said means responsive to said electrical output signal comprises a second silicon-controlled rectifier having its gate cathode circuit connected across said secondary windings, whereby the establishment of said electrical output signal across said secondary windings is effective to energize said second silicon-controlled rectifier to provide said trigger signal, and a third selectively energizable silicon-controlled rectifier is connected in shunt across said circuit breaker, said third silicon-controlled rectifier being coupled to said second silicon-controlled rectifier and being adapted to be rendered conductive in response to energization of said second silicon-controlled rectifier so as to define a low-resistance shunt conduction path across said circuit breaker in order to effect opening thereof in response to conduction of said third silicon-controlled rectifier.