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 circuit for monitoring the load current supplied by an uninterruptable power supply for transferring the load to a secondary source when the load current exceeds the capability of the uninterruptable power system. A signal representing the load current is simultaneously, continuously compared to a first reference level and a second reference level. The second reference level has a greater effective magnitude than the first reference level and whenever it is exceeded by the instantaneous signal the transfer is initiated. The transfer is also initiated whenever the signal uninterruptably exceeds the first reference level for a selected period of time.

Abstract: The analog electronic trip device comprises a time-lag tripping circuit formed by a non-linear function generator likely to elaborate by approximation the tripping characteristic of the circuit breaker.The device includes an integrating amplifier comprising a negative-feedback capacitor C and two inputs in phase opposition. One of the inputs is submitted to two threshold voltages V.sub.R1, V.sub.R2 determining the mode of long-time delay or short-time delay operation of the trip device. The second threshold voltage V.sub.R2 is set by a resistive switch which determines the short delay tripping threshold.

Abstract: An electronic system for a high amperage molded case circuit breaker employing a voltage to frequency converter circuit for transforming fault current levels to a number of pulses corresponding to the fault level. The pulses are applied to a long time delay and short time delay circuit respectively which integrates the pulses to provide an output in a time period inversely proportional to the fault level. The long time circuit is provided with a second stage activated for a selected time by each output of the respective first stage to further count the pulses and provide a long time delay output in a time period inversely proportional to the square of the fault current. A variable resistance power supply provides a fixed voltage drop across the current transformer output to facilitate changes in breaker rating with a simple rating resistor change. A bimetal switch is also employed to sense the temperature adjacent the breaker contacts.

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.

Abstract: A DC Solid State Overload Relay for use with a DC motor controller is provided with functions to provide instantaneous and delayed tripping of an overload relay by monitoring a standard ammeter shunt signal placed in the power line. The relay circuit uses dropping resistors and a sensing unit with the sensing unit containing separate presetable adjustment for the instantaneous and delayed tripping function and further has automatic reset provisions and a trip indicator which indicates the cause of relay tripping.

Abstract: A static instantaneous overcurrent relay with reduced transient overreach is provided for use in protecting an a-c power line from overcurrents. The relay operates on an input signal representative of the magnitude of the current in the a-c power line and develops a relay output signal when the magnitude of the current reaches a predetermined magnitude. In a preferred embodiment, the relay includes a level detector circuit for receiving the input signal which is in the form of a pulsating waveform having the same frequency as the a-c power line. The level detector circuit develops a discrete level detector output signal in response to each pulse of the waveform which attains a magnitude representative of the predetermined magnitude. Output circuit means is coupled to receive the discrete level detector output signals and includes temporary inhibit means for inhibiting the development of the relay output signal until the output circuit has received two of the discrete level detector signals.

Abstract: A static type overload relay is used to protect a motor against overload. The overload relay comprises an integrator for integrating the difference between the motor current and a continuous current carrying capacity of the motor. When the output of the integrator exceeds a predetermined value, a circuit breaker connected in series with the motor is tripped.

Abstract: A circuit breaker having an electronic fault sensing and trip initiating unit which provides increased versatility and ability to coordinate the circuit breaker with other interrupting and protective devices in a wide variety of electrical distribution systems. Electronic circuits and components are provided to vary the ampere rating of the breaker, to adjust current carrying capacity, to provide a long time delay trip, a short time delay trip and an instantaneous trip depending on the amplitude of high fault currents, to provide a ground fault trip, to shorten or lengthen the trip time for short time delay faults and for ground faults, and to provide shunt trip capability. The tripping mechanism is magnetic and mechanical, and includes a plunger movable between a trip and non-trip position controlled by an electronic switch in the electronic circuitry, and a toggle mechanism which is unlatched by the plunger when it moves to the trip position.

Abstract: A circuit breaker of the type having short delay and long delay tripping modules. Separate signals are provided as external outputs from the latter modules. Furthermore, inputs are provided to the latter modules for disabling the normal operation thereof. The above-mentioned breaker also includes an instantaneous tripping circuit. If the amount of overload current is sufficiently high, an instantaneous tripping operation takes place. If the overload current is relatively lower than that which would necessitate instantaneous tripping, short delay or long delay tripping will take place. If the current then continues to increase to a sufficiently high value, the circuit breaker will operate through the instantaneous tripping circuit.

Abstract: Power controllers comprising solid state elements responsive to control signals of low power from a remote control location selectively close and open relatively high power circuits to load devices, and including logic circuitry for opening selectively closed power circuits upon occurrence of overloads therein. The controllers also act upon their failure to respond to commands to open or close the power circuit by blowing a protective fuse in the former case and signaling in the latter. The controllers may employ power darlington switches for closing and opening the power circuits. All or most of the logic circuitry may function in providing the control and the overload or mode failure response for two or more load devices.