Solid state overcurrent detector

Claim 2

A solid state overcurrent detector comprising: current sensor means for issuing an output signal corresponding to overcurrent in an AC power line, level discriminator means for discriminating level of said output signal of said current sensor means, time-current operating means for issuing time-current operating signal responding to output signal of said level discrimination means, output means for issuing overcurrent detection signal responding to output signal of said time-current operating means and a charge-discharging circuit for being charged with a charge corresponding to heat energy produced by the overcurrent during operation of said time-current operating means and for discharging said charge with a predetermined time constant, said level discriminator and said time-current operating means being of microcomputer implemented configuration, comprising means for memorizing voltage remaining in said charge-discharge circuit, as an initial value for computing time-current operation, when another overcurrent takes place.

Claim 3

A solid state overcurrent detector in accordance with claim 1, wherein said charge-discharge circuit comprises a capacitor, charging means for charging said capacitor at reception of output signal controlled and issued from said microcomputer, and discharging means comprising at least a resistor to make a time-constant together with said capacitor for discharging an electric charge of said capacitor at said time-constant.

Claim 4

A solid state overcurrent detector in accordance with claim 2, wherein said microcomputer has means to issue a single pulse which has a width corresponding to time and intensity of the overcurrent.

Claim 5

A solid state overcurrent detector in accordance with claim 2, wherein said microcomputer has means to issue pulses wherein each pulse has a width corresponding to intensity of the overcurrent and said pulses continues during continuation of the overcurrent.

Claim 6

A solid state overcurrent detector in accordance with claim 1, wherein said current sensor means comprises a current transformer and said current transformer feeds power as operation power to said level discriminator, said time-current operating means, output means and said charge-discharge circuit.

Claim 7

A solid state overcurrent detector in accordance with claim 1, which further comprises a second current transformer which is for feeding power as operation power to said level discriminator, said time-current operating means, output means and said charge-discharge circuit.

Claim 8

A circuit interruptor comprising: disconnectable contacts provided in an AC power line, a releasing device for actuation of disconnection of the disconnectable contacts, and control means for controlling operation of the releasing means responding to an overcurrent under a predetermined condition, said control means comprising: current sensor means for issuing an output signal corresponding to overcurrent in an AC power line, level discriminator means for discriminating level of said output signal of the current sensor means, time-current operating means for issuing time current operating signal responding to output signal of the level discrimination means, output means for issuing overcurrent detection signal responding to output signal of said time-current operating means and a charge-discharging circuit for being charged with a charge corresponding to heat energy produced by the overcurrent during operation of the time-current operating means and for discharging the charge with a predetermined time constant, the level discriminator and the time-current operating means being of microcomputer implemented configuration, comprising means for memorizing voltage remaining in the charge-discharge circuit, as an initial value for computing time-current operation, when another overcurrent takes place.

Claim 9

A circuit interruptor comprising: disconnectable contacts provided in an AC power line, a releasing device for actuation of disconnection of the disconnectable contacts, and control means for controlling operation of the releasing means responding to an overcurrent under a predetermined condition, said control means comprising: current sensor means for issuing an output signal corresponding to overcurrent in an AC power line, level discriminator means for discriminating level of said output signal of the current sensor means, time-current operating means for issuing time current operating signal responding to output signal of the level discrimination means, output means for issuing overcurrent detection signal responding to output signal of said time-current operating means and a charge-discharging circuit for being charged with a charge corresponding to heat energy produced by the overcurrent during operation of the time-current operating means and for discharging the charge with a predetermined time constant, the level discriminator and the time-current operating means being of microcomputer implemented configuration, comprising means for memorizing voltage remaining in the charge-discharge circuit, as an initial value for computing time-current operation, when another overcurrent takes place.

Claim 10

A circuit interruptor in accordance with claim 7, wherein said charge-discharge circuit comprises a capacitor, charging means for charging said capacitor at reception of output signal controlled and issued from said microcomputer, and discharging means comprising at least a resistor to make a time-constant together with said capacitor for discharging an electric charge of said capacitor at said time-constant.

Claim 11

A solid state overcurrent detector in accordance with claim 8, wherein said microcomputer has means to issue a single pulse which has a width corresponding to time and intensity of the overcurrent.

Claim 12

A solid state overcurrent detector in accordance with claim 8, wherein said microcomputer has means to issue pulses wherein each pulse has a width corresponding to intensity of the overcurrent and said pulses continues during continuation of the overcurrent.

Claim 13

A solid state overcurrent detector in accordance with claim 7, wherein said current sensor means comprises a current transformer and said current transformer feeds power as operation power to said level discriminator, said time-current operating means, output means and said charge-discharge circuit.

Claim 14

A solid state overcurrent detector in accordance with claim 7, which further comprises a second current transformer which is for feeding power as operation power to-said level discriminator, said time-current operating means, output means and said charge-discharge circuit.