Abstract: A fast reacting ground fault interrupter circuit particularly suited for use with high current, high voltage DC pulses generated by transistor switched magnet pulsers driving pulsed electromagnets used with electromagnetic acoustic transducers (EMATs). Whenever a ground fault is detected, a digital shut off signal is sent to the transistor switched magnet pulser to shut it off and prevent transmission of the DC pulse. Additionally, the shut off signal is also provided to a DC current interrupter which shuts off power supplied to the transistor switched magnet pulser itself.

Abstract: The power supply, useful with an electromagnetic force apparatus such as a riveter or a bolt inserter, includes two capacitor banks which are charged through charging doubler modules. Each charging doubler module includes an AC capacitor which is responsive to a power source. The AC capacitor is connected to a node point between two diode elements, which are connected in series across the capacitor bank. An analog-to-digital converter converts the voltage on the capacitor bank to a digital voltage for comparison with a selected digital charge voltage in a controller. The selected digital charge voltage may vary over time by means of a compensating algorithm. A ground fault indicator using a biasing voltage is connected between a selected electrical circuit portion of the force apparatus and earth ground. A gas discharge tube in combination with a current sensing element is connected to the capacitor banks to determine a possible over-voltage condition.

Abstract: A circuit tester comprising a ground fault circuit interrupter having two pair of leads connected to opposite sides of the interrupter in series for connecting the ground fault interrupter between an electrical circuit and a power source to indicate current leakage in an amount greater than about 0.005 amperes, a method for utilizing the circuit tester for detecting amperage leakage in the circuit, and an electrical circuit which will be interrupted whenever there is ampere leakage above that magnitude.

Abstract: A ground fault interruption circuit detects a ground condition associated with a load in an electrical distribution system and disconnects the load in response to a ground fault condition. The circuit includes a ground fault detector connected to receive a ground fault imbalance signal and operative in response to a power signal, having specified voltage and current levels, to provide a trigger signal to disconnect the load from the system when the imbalance exceeds a certain level. A regulated power supply circuit a substantially constant current and voltage signal to the detector to minimize excess power to the detector and heat loss. The power supply includes a start up and storage portion and a constant current supply portion.

Abstract: Direct current can be measured by passing a conductor carrying the current through the core of a toroidal transformer having a bias winding and a sensing winding. A pulse generator send pulses of magnetization current through the sensing winding so that the magnetization current produces a magnetic flux in the core which opposes a magnetic flux produced by the direct current carried by the conductor. A sensing circuit, connected to the sensing winding, detects the level of current through that winding to produce a measurement of the direct current carried by the conductor. A constant direct current is applied through the bias winding to increase the magnetic flux produced by the direct current carried by the conductor. Biasing the magnetic flux enables even small currents flowing through the conductor to be measured. Another version of the current sensor uses two transformers to measure direct current flowing in either direction in the conductor and provides an indication of that current's polarity.

Abstract: A ground fault interruption circuit has a detector circuit coupled to an electrical distribution circuit load to detect ground fault conditions in the load. A filtering circuit connected between the detector circuit and distribution network comprises a pi-network filter for attenuating common-mode electromagnetic interference and differential-mode electromagnetic interference. The pi-network filter includes three filter portions which together provide a third order filter to attenuate the interference signals at the frequencies of interest.

Abstract: A ground fault interrupter 10 includes a core 12. Two load current-carrying wires 14, 16 pass through the core 12. A primary coil 44 is carried on the core 12 for sensing a current imbalance in the wires 14, 16. An auxiliary coil 18 is wound on the core 12. A pair of back-to-back zener diodes 20 is connected in series with the coil 18 to supply current to the coil 18 when an applied voltage exceeds a predetermined value between wires 14 and 16 or between either one of the and ground.

Abstract: An electrical supply safety plug that prevents power from a mains electrical supply from being accessible to an electrical appliance unless the electrical supply safety plug is properly engaged with the socket outlets and the appliance is turned on. The electrical supply safety plug disconnects the electrical appliance in the event of current imbalance.

Abstract: A ground fault circuit interrupter (GFCI) with built in intelligence is described that includes circuitry to automatically indicate a device miswiring condition. When a GFCI is wired with its AC and LOAD terminals reversed, downstream devices are still protected in the event of a ground fault but the duplex receptacle on the GFCI itself is not. The invention incorporates miswiring sense circuitry that automatically triggers the generation of visual and audible alarms in the event a miswiring condition is sensed. The invention employs an alarm inhibiting technique that incorporates sense circuitry connected to the AC terminals on one side of the internal GFCI switches or relays and alarm generation circuitry connected to the LOAD terminals on the opposite side.

Abstract: Ground fault trip units for circuit breakers are tested by a passive test circuit which includes a test conductor passing through the current transformer sensing coil(s), and a test switch which selectively connects the test conductor in a loop which simulates a neutral-to-ground fault. In a dormant oscillator ground fault test circuit, the test conductor loop passes through both sensing coils. When the neutral-to-ground detector is combined with a sputtering are fault detector sharing a common sensing coil, testing of all the components is accomplished by adding an additional test circuit which injects pulses derived from the line conductor into the sensing coil secondary, or which alternatively, connects a capacitor charged from a DC supply across the sensing coil secondary. Either of these alternative test circuits generates the successive events needed to produce a sputtering arc trip.

Abstract: An electronic trip device comprising, for each phase or neutral line, a rectifier bridge formed by four diodes which rectify the transformer current, a resistance for measuring the rectified current, and a circuit for detecting the sign or polarity of the measured current connected to one end of the transformer. A processing circuit calculates a value representative of the earth fault current by adding all the current values whose corresponding sign is positive and subtracting all the current values whose corresponding sign is negative. This current value is processed so as to bring about tripping when a threshold is exceeded for a preset time.

Abstract: A gas discharge device, such as a neon tube, is connected to a pair of output terminals of a power supply. The power supply has a transformer with a secondary winding that has first and second sub-windings. Each of the sub-winding is connected to a different output terminal and two conductors connect the first and second sub-windings to earth ground. A current sensor detects whether unequal magnitudes of current flow through in the two conductors. A resonant control circuit applies an excitation current to the primary winding of the transformer unless an imbalance of current flows. Thus excitation of the transformer is terminated when a high voltage ground fault occurs.

Abstract: An electrical circuit breaker device for connection between a load device and a power source, capable of disconnecting the load device from the power source upon detection of an electrical fault condition present in the wiring between the load and the power source is provided. A time delay prevents the load from being disconnected due to the reporting of a temporary voltage fluctuation. One embodiment of the present invention measures a voltage value representative of the voltage across the source and compares it with the voltage drop across the load to determine the voltage drop due to the wiring between the source and the load. The load device is disconnected from the power source if the resulting power loss or voltage difference due to the resistance of the wiring indicates a power loss in the wiring sufficient to cause combustion.

Abstract: In a ground fault circuit interrupter in which it was found that wide band noise induced by load transients is rectified by an op-amp in the detector circuit, false trips due to the wide band noise are eliminated by only comparing the output of the amplifier with a threshold of opposite polarity to that of the rectified noise signal and by eliminating capacitive coupling between the current sensor and the op amp. This requires an op amp with a low offset, on the order of about five percent or less.

Abstract: An invertor-controlled power unit includes an invertor circuit which performs switching control of direct current output from a direct current power source circuit in response to a driving signal. A bridge balanced circuit is connected to a pair of output lines extending from an output circuit of the power unit. The bridge balanced circuit has at least two balanced points and comprises a plurality of impedance elements connected to the pair of output lines. One of the balanced points is grounded. A potential difference between the one of the balanced points and another of same is detected, and a detection signal indicative of the potential difference is produced. When the detection signal falls outside a predetermined range, i.e. it is determined that a leak occurs, a stoppage instruction signal is produced to stop the supply of the driving signal to the invertor circuit.

Abstract: A hospital bed electrical power module for powering external medical devices directly from the bed includes electrical isolation circuitry connected to prevent external device leakage current from traveling through the bed frame. The power module reduces the risk of shock to the patient due to the leakage current of the external device.

Abstract: A device for protecting a power supply which is preferable for television receivers, etc. is disclosed. A diode is connected between a secondary anode of a power supply voltage feedback control photocoupler and a load of the power supply. When a voltage on the load is lowered due to an abnormality such as short-circuiting of the load, a control current for said power supply voltage feedback control photocoupler is caused to flow to the load via said diode to interrupt the control current for stopping the operation of the power supply. Overheating and/or breaking of components due to eddy current can be prevented on occurrence of an abnormality such as short-circuiting.

Abstract: A fault current circuit breaker has a summary current transformer whose secondary coil is connected to a voltage-independent energy storage circuit. A monostable or bistable transformer relay is actuated by an impulse by way of this energy storage circuit when a fault current flows to earth in the protected installation. When the relay contact is made, an electromagnetic lock trigger is actuated by the energizing current received from the mains supply, which triggers the switch lock of the FC switch. After this, the bistable transformer relay is returned to its initial position, either mechanically by way of an appropriate coupling with the switch lock, or electrically by way of a time delay or switch circuit, whereby the relay contact opens and the FC switch is again ready for switching on.

Abstract: A GFCI receptacle has a receptacle and terminals for connecting the connectors of that receptacle to an AC source, terminals for connecting the connectors of the receptacle to one or more other loads and an interrupter for disconnecting the source from the receptacle and the other loads in the event of ground current exceeding a selected level. For testing the interrupter, a manually operable supervisory circuit opens the interrupter and gives a visible indication of its operation. The supervisory circuit is connected between a hot connector of the receptacle and ground so that the visible indication will not be visible when the GFCI receptacle is installed improperly, thereby avoiding a false indication of proper installation.

Abstract: A protective device for an externally powered electrical apparatus is disclosed. The protective device is designed to prevent accidental electrocution of the user if the power supply is subject to a short circuit. The protective device is an electromechanical device incorporating a device for detecting current differentials between non-ground electrical conductors, a normally closed switch in association with a fuse device, and a trigger circuit for terminating the current flow through the electrical apparatus when a short circuit is detected.

Abstract: Apparatus for remotely controlling electrical equipment includes a ground fault interrupter circuit having a selectively operable circuit breaker for connecting and disconnecting power to the electrical equipment, a transmitter for generating amplitude modulated electromagnetic radiation when it is desired to operate the circuit breaker, and a receiver responsive to the electromagnetic radiation for selectively operating the circuit breaker.

Abstract: A ground fault interruptor (GFI) electrical connector receptacle device for use with a twist-lock, multi-prong plug has passages in the face plate in registration with electrical contact blades coupled to a GFI circuit to disconnect the blades upon detection of a ground fault. The configuration and shape of the passages through the face plate accept the twist-lock plug so that the foot of the L-shaped grounding prong of the plug is brought into engagement with the rear surface of the housing face plate when the plug is rotated to restrain the plug from axial removal.

Abstract: An electrical connector with the function of instantaneous breaking of a current in response to detection of a leak. The connector comprises: a current supply cord for connecting a load to a source; a pair of plug blades connected electrically with the current supply cord and projected out of a connector body; a sensor mounted in the connector body for detecting a current leak; a breaker device for breaking the connection between the plug blades and the current supply cord in response to a detection by the leak detection sensor.

Abstract: A personnel protection system for electrical connections is disclosed, which is of the type that differentially senses the current flow between the power lead and the return lead (or between two power loads) is provided with an unbalancing impedance which makes the current difference between the two leads sufficiently high to trip the device and cause the power to be disconnected. A utilization device is similarly provided with an imbalanced impedance. However, that impedance is calculated to counteract the current imbalance caused by the first impedance, so that when the cable is connected to the utilization device, the current balance between the two conductors is restored, and power connection is maintained in the cable. Thus, the system does not provide continuous power unless predetermined conditions considered safe for securing the power are fully satisfied.

Abstract: A personnel protection system for electrical connections is disclosed, which is of the type that differentially senses the current flow between the power lead and the return lead (or between two power loads) is provided with an unbalancing impedance which makes the current difference between the two leads sufficiently high to trip the device and cause the power to be disconnected. A utilization device is similarly provided with an imbalanced impedance. However, that impedance is calculated to counteract the current imbalance caused by the first impedance, so that when the cable is connected to the utilization device, the current balance between the two conductors is restored, and power connection is maintained in the cable. In addition, the current flow in the second impedance is sensed and, if it is not at the correct level, electrical power to the load is disconnected in the same manner as when an imbalance occurs.

Abstract: What is described is an electrical safety socket arrangement, comprising live and neutral socket inlets, switches connecting the live and neutral socket inlets to respective live and neutral socket outlets, and a circuit control which operates the switches when live and neutral supply feeders are connected to the socket inlets and a circuit is completed such that the circuit is completed by the connection of an appliance across the live and neutral socket outlets.

Abstract: A transformer ground fault protector is provided and includes sensing means in the form of at least one conductive plate adjacent but spaced from the output of each secondary winding in a transformer having its secondary windings connected in series and at the midpoint of the series circuit to ground. The at least one conductive plate forms a capacitive circuit with the windings and provides an output voltage when the secondary windings are energized and unbalanced. The output voltage generated by the at least one conductive plate in normal operation of the transformer, is substantially equal to zero volts. However, when a fault occurs in the transformer, the output voltage induced in the at least one conductive plate has a magnitude greater than zero. The resultant voltage in turn is conveyed to a comparator which compares the magnitude of the resultant voltage with a predetermined threshold voltage.

Abstract: Disclosed is a helically wound core of ferrous material used as a differential current sensor core in the ground fault sensor of a ground fault interrupter circuit. The ferrous material comprises a single strand of wire which is wound in helical fashion to create a tubular shaped core comprising a series of wire loops (all part of the single strand) parallel to each other and running the length of the tubular shape. The core is placed around a pair of current carrying lines to be monitored for ground faults (one line leading to and one line leading away from the power source) to interact with the magnetic fields of the lines. Toroidally wound leads wrapped around the wire core act as a secondary and are connected to a ground fault interruption circuit to shut off the power to the conducting lines in the event that the sensor detects a difference in current in the lines.

Abstract: An earth current leakage breaking circuit detects a current leakage in an AC line in a copying apparatus and breaks electrically the AC line. The circuit has a current difference detector which detects a difference in current between an incoming current and an outgoing current in AC lines which supply electric power from an AC power source to electrical loads in the apparatus. A control circuit which, when it detects an output signal from the current difference detector which continuously exceeds a reference level, turns off a relay provided to the AC lines. The control circuit has a timing generator which generates timings to start driving the loads, and a reference level generator which generates the reference level being variable in accordance with the generated timings.

Abstract: A ground fault interrupt circuit with an improved current window detector. The current window detector works by first rectifying the input current in a pair of current mirrors connected in back to back fashion in the feedback path of the input amplifier. The rectified current triggers an output when the rectified current exceeds a predetermined threshold.

Abstract: A circuit breaker bandwidth limits a sensed rate of change of current, di/dt, in the neutral conductor of a protected electrical system and fullwave rectifies the bandwidth limited di/dt signal for comparison with an instantaneous trip reference signal. The bandwidth is selected to provide a selected relative sensitivity of the instantaneous trip to sinusoidal currents associated with overcurrent faults and step currents associated with sputtering arc faults. The rectified bandwidth limited di/dt signal is also filtered and delayed for comparison with a delayed trip reference signal. The time constant for the filter is selected to provide a selected relative sensitivity of the delayed trip to overcurrent faults and sputtering arc faults. A low mu sensing coil used to generate the di/dt signal can also serve as the neutral current sensing coil of a dormant oscillator ground fault protection system.

Abstract: A circuit interrupter is disclosed which provides for tripping of a line lead on occurrence of a loss of neutral or an earth leakage fault without the need for an earth connection. The circuit interrupter includes a circuit breaker which is activated by discharge of a capacitor in a closed loop, the capacitor being connected across the output of a D.C. power supply. A loss of neutral fault is detected as the potential of a neutral lead rises through a pull-up resistor and tripping will occur before the neutral rises to a potential at which the power supply becomes inoperative.

Abstract: A miniature circuit interrupter for interruption of a primary circuit, the circuit interrupter formed or molded with a plug, connector or the like, the plug or connector being non-serviceable and the circuit interrupter therein being sealed and watertight.

Abstract: A differential current circuit breaker is disclosed in operation with a transductor circuit. The transformer has a secondary winding which is coupled to a measuring resistor in series with a generator, in particular a square wave generator, for alternating magnetization. The circuit breaker includes an evaluation circuit coupled to a tripping mechanism that acts through a breaker mechanism on switching contacts in the conductors being monitored. The evaluation circuit is coupled to a tap between the secondary winding and the measuring impedance. The generator capable of setting the generator frequency within a larger frequency range than is required to compensate for tolerance adjustment in the generator itself.

Abstract: A device and method for interrupting current flow to an electrically-powered apparatus is disclosed. The device includes a means for detecting a selected value of a physical parameter associated with the operation of the externally powered electrical apparatus, a trigger circuit incorporating an integrated circuit, a firing device which responds to the trigger circuit by generating a conductive plasma, an electronic measurement circuit to prevent unwanted firing of the firing device and thin conductors which are destroyed by the firing device when the conductive plasma forms an electric arc between them. Current flow to the electrically-powered apparatus is thereby terminated.

Abstract: An arc detection method and apparatus is provided for an electric circuit having an electrified conductor (46) connecting a voltage source (26) to a load (30). A field sensor senses an electromagnetic field established about the conductor by the occurrence of an electrical arc in the circuit, and generates a field responsive signal. Arc discrimination circuitry includes frequency responsive circuitry responding to the field sensor and generating an arc indicative signal in response to a given frequency characteristic of the field responsive signal. The frequency responsive circuitry monitors a plurality of different frequencies of the field responsive signal, and generates the arc indicative signal in response to a given combination of field responsive signal frequencies. A comb filter passes the field responsive signal through a plurality of passbands, and the arc indicative signal is generated in response to a given frequency signature of the field responsive signal.

Abstract: An arc detection method and apparatus is provided for an electric circuit having an electrified conductor (46) connecting a voltage source (26) to a load (30). The system senses the electromagnetic field established about the conductor by the occurrence of an electrical arc in the electric circuit, and generates a field responsive signal. Arc discrimination circuitry responding to the field responsive signal and generates an arc indicative signal in response to a given characteristic of the field responsive signal. The system includes an E field sensor (66) and a B field sensor (68).

Abstract: An arc detection method and apparatus is provided for an electric circuit having an electrified conductor (46) connecting a voltage source (26) to a load (30), the conductor having a line side extending from the arc detector to the voltage source, and a load side extending from the arc detector to the load. The arc detector includes a field sensor (62) sensing the electromagnetic field established about the conductor by the occurrence of an electrical arc in the circuit, and generating a field responsive signal in response thereto. Direction sensing circuitry detects whether the arc is from the load side or the line side, and generates a direction indicative signal.

Abstract: An arc detection method and apparatus is provided for an electric circuit having an electrified conductor (46) connecting a voltage source (26) to a load (30). The arc detector includes a field sensor (62) sensing an electromagnetic field established about the conductor by the occurrence of an electrical arc in the electric circuit, and generating a field responsive signal in response thereto. Arc discrimination circuitry responds to the field sensor and generates an arc indicative signal in response to a random chaotic pattern of the field responsive signal.

Abstract: A plug-in ground fault interrupting type circuit breaker includes a resilient jaw for engaging the neutral bar in a loadcenter. The jaw is formed at the end of a conductive strap which passes through the window of a transformer and terminates in a screw terminal for attachment to a neutral load conductor. The phase conductive path also includes a conductive strap that is coupled at one end to a phase load conductor terminal and at its other end to the breaker trip mechanism. The transformer and both strap conductors are mounted to a printed circuit board that is included within the breaker housing. The invention eliminates the separate pigtail for connecting the load neutral conductor to the loadcenter neutral bar.

Abstract: A ground fault interruptor circuit interrupts the flow of current to a pair of lines extending between a source of power and a load. The ground fault interruptor circuit includes a circuit breaker comprising a normally open switch located in one or both of the lines, a relay circuit for selectively closing the normally open switch, an electronic latch circuit operable in first and second bi-stable states and a fault sensing circuit for sensing the presence of a fault condition in at least one of the lines. The electronic latch circuit causes the relay circuit to close the normally open switch and maintain the normally open switch in its closed position when the electronic latch circuit is in the first bi-stable state. The electronic latch circuit also causes the relay circuit to permit the normally open switch to return to its normally open condition when the latch circuit is in its second bi-stable state.

Abstract: A neutral line circuit interrupter having a switch in the neutral voltage line to trigger the interrupter upon the occurrence of a predetermined event to disconnect the line voltage from the load. Both contacts of the switch are at the identical, neutral voltage level so that the switch is not subject to a high voltage and can be used in remote locations where the presence of a high voltage would be undesirable.

Abstract: An arrangement for opening a circuit coupled to an electrical power source associated with a neutral circuit. The arrangement includes a bi-stable latch for electrically engaging and disengaging a pair of contacts in response to the value of the sum of currents in the circuit and the neutral circuit exceeding a predefined limit. The arrangement also includes a mechanism for opening and closing a pair of main contacts which are used to open and close the circuit. The mechanism can be operated by a shunt trip solenoid such that the solenoid causes the operating mechanism to open the contacts when the contacts of the bi-stable latch are closed.

Abstract: A current of an alternating current electric line is detected by a current transformer, the output of the current transformer is rectified by a rectifier, a series connection of a switching means and a resistor is coupled across the output terminals of the rectifier, a control circuit composed of a capacitor, a comparator and a reference voltage generator is coupled in parallel to the switching means through a diode, when the DC output voltage exceeds a predetermined voltage based on the reference voltage of the reference voltage generator, the comparator outputs a signal for closing the switching means, and the voltage which is applied to the control circuit is limited to a predetermined value.

Abstract: An arcing fault detector is set up to identify arcing faults and to distinguish them from other disturbances in a circuit. A plurality of electrical conditions are monitored and the conditions are tested against predetermined parameters for establishing a series of logical conditions relating to the presence of an arcing fault. A logic circuit combines the logical conditions for deciding on the presence of an arcing fault. An output signal of the logic circuit is used to activate a relay for interrupting the supply of electrical power to the circuit.

Abstract: An improved grounding detection circuit includes an intrinsically safe circuit connected to a grounding clip for grounding vehicles and container durng the transfer and storage of combustible materials. The intrinsically safe circuit includes grounding loop for verifying that the grounding clip and the intrinsically safe circuit are grounded. The intrinsically safe circuit transmits a signal to an optoisolator when the container is grounded, and the optoisolator, in turn, transmits an energization signal to relay circuitry, to energize a relay coil. A capacitor in series with a resistor are connected across the relay coil to minimize the inductive effect of the relay coil on the optoisolator.

Abstract: A safety device for minimizing electrical shock to a user is taught. Briefly stated, a ground plane is disposed inside an electrical tool or device. Should the device become immersed in water or become unreasonably wet, the plane provides a path of electrical current, which energizes an interrupt device contained therein. The interrupt device disconnects power from the device. Further, reset can only be accomplish by a special purpose tool being urged through an aperture in the device case.

Abstract: In a power-line-operated power-factor-corrected electronic ballast, a pair of series-connected fluorescent lamps is powered via a tuned L-C circuit that is series-excited by the rectangular-wave 33 kHz voltage output of a half-bridge inverter and parallel-loaded by the fluorescent lamps. Power factor correction is attained via two energy-storing capacitors charged during periods when the instantaneous absolute magnitude of the power line voltage exceeds half of its peak absolute magnitude and discharged when it fails to exceed half of this peak absolute magnitude. As a result, a so-called valley-filled DC voltage is provided to the inverter; which results in the inverter's rectangular-wave output voltage being about 50% amplitude-modulated. In spite of this high degree of amplitude-modulation, the resulting lamp current crest factor is only about 1.8.

Abstract: A differential protective relay apparatus is switched over between a current differential mode and a voltage differential mode automatically by both even-order harmonic components of an imput applied to a differential circuit and a voltage across an impedance of the differential circuit, thereby to cover extensive fault modes while retaining high minimum pickup sensitivity, furthermore, devised against excessive fault voltages in the voltage differential mode, and, consequently, advantageous in insulation withstand capability.

Abstract: Device for detecting the quenching of part a superconducting element comprising two identical superconducting conductors electrically connected in parallel is provided with means (104, 105, 109, 110) of detecting a difference in intensity or phase between the currents flowing in the conductors. An application to a superconducting current limiter is described.