Instantaneous and inverse-time-overcurrent sensor

Claim 2

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means including selectively adjustable means coupled to said first means for generating a first current signal as a desired nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic and operable on a different portion of its transfer characteristic, dependent upon the adjustment of said selectively adjustable means, to generate said first current signal as said desired nonlinear function of said first voltage signal; and third means coupled to said second means for generating a second voltage signal as a function of the time integral of the first current signal.

Claim 3

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means coupled to said first means for generating a first current signal as a nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic; and third means coupled to said second means for generating a second voltage signal as a function of the time integral of the first current signal; wherein said solid-state device is a transistor having collector, base and emitter terminals with the base and emitter terminals coupled across said first means, and said emitter terminal further coupled to said third means.

Claim 4

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means coupled to said first means for generating a first current signal as a nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic; and third means coupled to said second means for generating a second voltage signal as a function of the time integral of the first current signal; wherein said solid-state device is a transistor having collector, base and emitter terminals with the base and emitter terminals coupled across said first means, and said emitter terminal further coupled to said third means.

Claim 5

The device of claim 2 further comprising resistive means for coupling the emitter terminal to said first and third means.

Claim 6

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means coupled to said first means for generating a first current signal as a nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic; third means coupled to said sEcond means for generating a second voltage signal as a function of the time integral of the first current signal; wherein said solid-state device is a transistor having collector, base and emitter terminals with the base and emitter terminals coupled across said first means, said emitter terminal further coupled to said third means, and further comprising resistive means for coupling the emitter terminal to said first and third means; and wherein said resistive means includes a nonlinear voltage dependent resistor.

Claim 7

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means coupled to said first means for generating a first current signal as a nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic; third means coupled to said sEcond means for generating a second voltage signal as a function of the time integral of the first current signal; wherein said solid-state device is a transistor having collector, base and emitter terminals with the base and emitter terminals coupled across said first means, said emitter terminal further coupled to said third means, and further comprising resistive means for coupling the emitter terminal to said first and third means; and wherein said resistive means includes a nonlinear voltage dependent resistor.

Claim 8

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means coupled to said first means for generating a first current signal as a nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic; third means coupled to said second means for generating a second voltage signal as a function of the time integral of the first current signal; wherein said solid-state device is a transistor having collector, base and emitter terminals with the base and emitter terminals coupled across said first means, said emitter terminal further coupled to said third means, and further comprising resistive means for coupling the emitter terminal to said first and third means; and wherein said second means includes a potential source having a first terminal coupled to said collector and having a second terminal; said third means includes a first resistive device coupled in series with an energy storage element; said third means being coupled between said resistive means and said second terminal, with said first resistive device connected to said resistive means, and said energy storage element connected to said second terminal.

Claim 9

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means coupled to said first means for generating a first current signal as a nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic; third means coupled to said second means for generating a second voltage signal as a function of the time integral of the first current signal; wherein said solid-state device is a transistor having collector, base and emitter terminals with the base and emitter terminals coupled across said first means, said emitter terminal further coupled to said third means, and further comprising resistive means for coupling the emitter terminal to said first and third means; and wherein said second means includes a potential source having a first terminal coupled to said collector and having a second terminal; said third means includes a first resistive device coupled in series with an energy storage element; said third means being coupled between said resistive means and said second terminal, with said first resistive device connected to said resistive means, and said energy storage element connected to said second terminal.

Claim 10

The device of claim 3 wherein said first means includes adjustment means for varying the coupling between said first and second means; whereby the nonlinear response of said second means varies with the setting of said adjustment means.

Claim 11

The device of claim 5 wherein said storage element comprises a capacitor.

Claim 12

The device of claim 5 further including a second resistive device coupled between the junction of the first resistive device and the resistive means, and the second terminal.

Claim 13

The device of claim 5 wherein said first means comprises current transformer means inductively coupled to said circuit; a rectifier coupled across the output of the current transformer means; and a potentiometer connected across said rectifier output terminals with the wiper output terminal of said potentiometer coupled to said base terminal; whereby the nonlinear response of said second means varies with the position of the wiper.

Claim 14

The device of claim 5 wherein said first resistive device is a variable resistor.

Claim 15

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means coupled to said first means for generating a first current signal as a nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic; third means coupled to said second means for generating a second voltage signal as a function of the time integral of the first current signal; fourth means, coupled to said conductor, for generating a first control signal when the current in said conductor exceeds a first predetermined level; and fifth means coupled to said fourth means and responsive to said first control signal for clamping said second voltage signal to a second predetermined reference level when the current in said conductor is below the first predetermined predetermined level.

Claim 16

In a system for monitoring the time-current relationship in a conductor: first means for generating a first voltage signal representative of the current in said conductor; second means coupled to said first means for generating a first current signal as a nonlinear function of said first voltage signal, said second means including a solid-state device having a nonlinear input voltage-output current transfer characteristic; third means coupled to said second means for generating a second voltage signal as a function of the time integral of the first current signal; fourth means, coupled to said conductor, for generating a first control signal when the current in said conductor exceeds a first predetermined level; and fifth means coupled to said fourth means and responsive to said first control signal for clamping said second voltage signal to a second predetermined reference level when the current in said conductor is below the first predetermined predetermined level.

Claim 17

The device of claim 11 wherein said third means incluDes a bank of selectable energy storage elements for storing said first current signal; said fourth means includes a comparator and a voltage reference circuit; and said fifth means includes a transistor switching circuit coupled across said bank of selectable storage elements and controlled by the output signal of said comparator circuit.

Claim 18

The device of claim 12 wherein said voltage reference circuit comprises adjustment means for varying the reference level of said fourth means.

Claim 19

The device of claim 12 further comprising first actuation means coupled to said third means for developing a first actuation signal when said second voltage signal exceeds a third predetermined voltage level.

Claim 20

The device of claim 14 wherein said first actuation means includes a unijunction device having first and second base terminals coupled across a potential source, having an emitter terminal; and further includes means for applying said second voltage signal to the emitter terminal of said unijunction device.

Claim 21

The device of claim 11 further comprising second actuation means, coupled to said first means, for developing a second actuation signal when said first voltage signal exceeds a third predetermined voltage level.

Claim 22

The device of claim 14 further comprising tripping means for interrupting the current in said conductor upon the generation of said first actuation signal.

Claim 23

The device of claim 14 further comprising second actuation means for generating a second actuation signal when the current in said conductor exceeds a selected current value; and tripping means for interrupting the current in said conductor in response to either one of the first and second actuation signals.

Claim 24

The device of claim 18 further comprising first indicator means for indicating the occurrence of the first actuation signal.

Claim 25

The device of claim 19 further comprising second indicator means for indicating the occurrence of the second actuation signal.

Claim 26

The device of claim 20 further comprising level indicator means for indicating the occurrence of said first actuation signal.