Abstract: An improved current-sensing arrangement and method are provided for supplying a signal that suitably represents line current over a wide current range. The current-sensing arrangement utilizes the signals from an iron core transformer and an air core transformer along with transition and scaling arrangements to provide the sensed current signal. The range of operation includes currents for which the iron core transformer exhibits saturation effects and currents for which the air core transformer does not contribute to the combined output signal. Additionally, the range of operation includes currents for which both the transformers contribute to the combined output signal.

Abstract: A trip signal generator comprises a circuit possessing an inverse time-current characteristics for producing a trip signal in response to the occurrence of overcurrent in an alternating current line. The trip signal is produced after the passage of some time period, which varies inversely with the difference between the absolute magnitude of the overcurrent and a threshold current. The circuit includes a portion which produces pulses at a rate proportional to the difference between the absolute magnitude of the overcurrent in the line and the threshold current. The circuit produces no pulses when the line current is less than or equal to the threshold current. The circuit includes a counter for counting the pulses and for producing the trip signal after the counting of a selected number of pulses. Another portion of the circuit enables the counter when overcurrent is in the line, but resets the counter and prevents its operation when the line current is less than or equal to the threshold current.

Abstract: A control circuit is provided for operating a circuit interrupter in response to overcurrent in an alternating-current line in which the circuit interrupter is located. The control circuit includes a transducer for producing output current proportional to the current in the line. A time-current trip signal generator circuit responds to output current representative of moderate overcurrent in the line by producing a trip signal after the passage of a time period that is inversely related to the overcurrent. An instantaneous trip signal generator circuit produces a trip signal after a predetermined time interval in response to output current between a minimum and maximum magnitude and increasing at a rate greater than a selected rate, which conditions indicate the presence of high overcurrent in the line. In the preferred arrangement, the predetermined time interval is measured from the time that the rate of change of the current exceeds a predetermined rate.

Abstract: A control circuit is provided for applying energy to operate a circuit interrupter in response to, and a selected time after, the onset of overcurrent in an alternating-current line. The control circuit includes a transducer for producing output current proportional to the current in the line. The power supply includes an energy storage circuit that stores energy derived from the output current. The stored energy, which is maintained within a first range when there is no overcurrent in the line, energizes the power supply. A time-current trip signal generator circuit responds to output current representative of moderate overcurrent in the line by producing a trip signal after the passage of a time period that is inversely related to the overcurrent.

Abstract: A power supply is provided for energizing a trip signal generator and for selectively operating a device in response to the detection by the trip signal generator of overcurrent in a alternating current line. The power supply receives input of full-wave rectified current that is directly proportional to the alternating current in the line. A regulator circuit is also provided to power the trip signal generator and other circuitry. When current initially flows in the line the regulator rapidly produces an output voltage approximately equal to the input voltage up to a first voltage level. When the input voltage exceeds that level, the output voltage of the regulator increases at a slower rate than the input voltage to permit regulation of the output voltage. When energized, the output voltage is regulated at a predetermined constant level. The power supply also includes an energy storage circuit for supplying the input voltage to the regulator and to a circuit interrupter when desired.