Protection system with manual reset means operable only on clearing of the fault

Claim 2

A protection system for effecting disruption of the power being supplied to a load responsive to a sensed variation in the operation of a system being protected comprising; a first selectively operable switch means for connecting and disconnecting the load from a source of power in response to closing and opening thereof, a first selectively energizable switch control means operatively connected to said first switch means adapted to effect opening of said first switch means responsive to energization thereof, said first switch means maintained in its open condition until a neutralizing operation is effected, a selectively energizable current switch coupled to said switch control means, said current switch effecting energization of saiD switch control means responsive to conduction thereof, means responsive to the operation of the system being protected for rendering said current switch conductive responsive to a preselected variation in the operation of the system being protected, and selectively operable neutralizing means coupled to said current switch and to said switch control means for effecting said neutralizing operation only when said current switch returns to a non-conductive condition.

Claim 3

A protection system in accordance with claim 1 wherein said means responsive to the operation of the system being protected comprises a variable impedance, the impedance of which varies responsive to variations in the operation of the system being protected.

Claim 4

A protection system in accordance with claim 2 wherein said means responsive to the operation of the system being protected includes a voltage divider having a pair of legs defining a junction, one of said legs being connected to said variable impedance, whereby first and second preselected voltage levels are established at said junction responsive to first and second impedance values of said variable impedance corresponding to desired and undesired operation respectively of the system being protected.

Claim 5

A system in accordance with claim 3 wherein said current switch is coupled to said voltage divider junction and is adapted to be rendered conductive responsive to establishment of said second preselected voltage level at said junction, thereby energizing said switch control means.

Claim 6

A system in accordance with claim 4 wherein said current switch comprises a transistor having its base coupled to said voltage divider junction and having its collector-emitter circuit serially coupled to said switch control means, said collector-emitter circuit defining a low impedance current path upon conduction of said transistor while substantially precluding current flow therethrough upon non-conduction of said transistor.

Claim 7

A system in accordance with claim 4 wherein said switch control includes a first relay coil coupled to said current switch, said first relay coil being energized responsive to current flow through said current switch for rendering said first switch means non-conductive upon the initiation of current flow through said first relay coil causing magnetic retention of said first switch means in a non-conductive condition.

Claim 8

A system in accordance with claim 6 wherein said neutralizing means includes a second selectively energizable relay coil adapted to selectively neutralize the magnetic retention of said first switch means in a non-conductive condition responsive to current flow through said second relay coil.

Claim 9

A system in accordance with claim 7 wherein said first relay coil comprises a latch coil serially connected to said current switch, said latch coil effecting opening and retaining in an open condition of said first switch means until current flow is established through said second relay coil.

Claim 10

A system in accordance with claim 8 wherein said second relay coil comprises an unlatch coil connected in shunt relationship with said latch coil.

Claim 11

A system in accordance with claim 9 wherein means are provided for electrically isolating said unlatch coil from the source of power to prevent current flow therethrough when said current switch is in a conductive state.

Claim 12

A system in accordance with claim 10 wherein said means for electrically isolating said unlatch coil from the source of power comprises a unidirectional switch connected between said unlatch coil and said current switch, said unidirectional switch being rendered conductive for shunting current flow from said unlatch coil through said current switch when said current switch is in a conductive state.

Claim 13

A system in accordance with claim 11 wherein said unidirectional switch comprises a diode.

Claim 14

A system in accordance with claim 11 wherein a selectively operable reset switch is coupled between the source of power and said unlAtch coil for effecting current flow through said unlatch coil upon closure thereof only when said current switch remains in a non-conductive condition.

Claim 15

A protection system for disrupting the power to a load responsive to a sensed fault condition and precluding the re-application of power to the load prior to dissipation of the fault condition comprising; a first normally closed switch means for connecting the source of power to the load, a relay including a latch coil operatively connected to the switch means for effecting opening thereof upon energization of said latch coil, said latch coil permitting a magnetic bias to effect retention of said switch means in an open condition subsequent to de-energization thereof, and an unlatch coil for effecting neutralization of the magnetic bias upon energization of said unlatch coil, a normally non-conductive semi-conductor switch device having a voltage responsive control element for controlling conduction thereof serially connected to said latch coil and connected in shunt across said unlatch coil for effecting energization of said latch coil and preventing energization of said unlatch coil upon conduction thereof, sensing means coupled to said control element for controlling conduction of said semi-conductor switch, said sensing means including a variable impedance coupled to the power source whereby a variation in its impedance responsive to a sensed fault condition varies the voltage established thereacross so as to render said semi-conductor switch device conductive, a selectively operable reset switch coupled between the power source and said unlatch coil for effecting energization thereof upon closure of said reset switch, said reset switch being connected in shunt with said latch coil for positively shunting current from said latch coil only when said semi-conductor current switch device is rendered non-conductive upon dissipation of the fault condition, and shunt switch means coupled between said unlatch coil and said reset switch, said shunt switch means being rendered conductive responsive to conduction of said semi-conductor switch for shunting current away from said unlatch coil until said semi-conductor switch is rendered non-conductive whereupon current flow through said unlatch coil is permitted.

Claim 16

A protection system for disrupting the power to a load responsive to a sensed fault condition and precluding the re-application of power to the load prior to dissipation of the fault condition comprising; a first normally closed switch means for connecting the source of power to the load, a relay including a latch coil operatively connected to the switch means for effecting opening thereof upon energization of said latch coil, said latch coil permitting a magnetic bias to effect retention of said switch means in an open condition subsequent to de-energization thereof, and an unlatch coil for effecting neutralization of the magnetic bias upon energization of said unlatch coil, a normally non-conductive semi-conductor switch device having a voltage responsive control element for controlling conduction thereof serially connected to said latch coil and connected in shunt across said unlatch coil for effecting energization of said latch coil and preventing energization of said unlatch coil upon conduction thereof, sensing means coupled to said control element for controlling conduction of said semi-conductor switch, said sensing means including a variable impedance coupled to the power source whereby a variation in its impedance responsive to a sensed fault condition varies the voltage established thereacross so as to render said semi-conductor switch device conductive, a selectively operable reset switch coupled between the power source and said unlatch coil for effecting energization thereof upon closure of said reset switch, said reset switch being connected in shunt with said latch coil for positively shunting current from said latch coil only when said semi-conductor current switch device is rendered non-conductive upon dissipation of the fault condition, and shunt switch means coupled between said unlatch coil and said reset switch, said shunt switch means being rendered conductive responsive to conduction of said semi-conductor switch for shunting current away from said unlatch coil until said semi-conductor switch is rendered non-conductive whereupon current flow through said unlatch coil is permitted.

Claim 17

A system in accordance with claim 14 wherein said shunt switch means comprises a diode having one terminal connected intermediate said reset switch and said unlatch coil and its other terminal coupled to said semi-conductor switch.

Claim 18

A system in accordance with claim 15 wherein said semi-conductor switch comprises a transistor having its base coupled to said sensing means and its collector-emitter circuit serially connected to said latch coil and in shunt across said unlatch coil.