Solid state trip circuit with digital timer

Details Solid state trip circuit with digital timer Solid state trip circuit with digital timer

1982-03-26

1984-04-10

Miller, Jr., George H.

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific current responsive fault sensor

361 95, 361 97, H02H 726

Patent

active

044424728

ABSTRACT:
An electrical circuit is provided for actuating the trip mechanism of a circuit interrupter and includes a current sensor having a pair of output terminals and designed to cooperate with at least one electrical power conductor to sense the amount of current flowing in that conductor. The circuit further includes a circuit neutral terminal. A power supply is provided having input terminals with one of the input terminals being connected to one of the output terminals of the current sensor for receiving the sensed current signal therefrom, the other of the input terminals being connected to the circuit neutral terminal. The power supply produces output power at a first voltage level during a first mode of operation of the electrical circuit and produces output power at a second voltage level during a second mode of operation of the electrical circuit, with the second voltage level being substantially higher than the first voltage level. Circuitry is connected to the circuit neutral terminal and the other of the output terminals of the current sensor for developing a voltage signal proportional to the sensed current signal. Control circuitry is provided responsive to the magnitude of the voltage signal for actuating the trip mechanism of the circuit interrupter when the current flowing in the electrical power conductor exceeds a predetermined level. When said electrical circuit is in said first mode of operation, the control circuit is connected to the power supply for receiving output power at the first voltage level. When the electrical circuit is in the second mode of operation, the control circuit is connected to the power supply circuit for receiving output power at the second voltage level. The control circuit further includes at least one amplifier circuit for amplifying the voltage signal to a desired level. The amplifier circuit includes a gain changing circuit to adjust the level at which the trip mechanism will be actuated. The control circuit further includes a digital timing circuit having a first signal producing circuit responsive to the magnitude of the voltage of the signal received at the input terminal of the timing circuit for producing pulses having a first frequency. The timing circuit further includes a second signal producing circuit responsive to the magnitude of the voltage of the signal received at the input terminal of the timing circuit for producing pulses having a second frequency. A gate circuit is connected to the first and second signal producing circuits for producing output pulses only when receiving pulses from both the first and second signal producing circuits. A counting circuit is connected to the gate circuit for counting the number of the output pulses whenever the magnitude of the voltage at the input terminal exceeds a predetermined level.

REFERENCES:
patent: 4149210 (1979-04-01), Wilson
patent: 4347541 (1982-08-01), Chen et al.

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