Abstract: Electrical systems, especially elongate heating systems, include means for monitoring circuit continuity and/or absence of ground faults. The systems comprise a switching device, e.g. a thermostat, as well as a circuit breaker. When the switching device is on, a relatively high current passes through the circuit and when it is off, little or no current passes through the circuit. In one embodiment, a small controlled residual current flows in the circuit even when the switching device is off, and a current-detecting device signals when a discontinuity causes the current to drop below the expected value for the residual current. In another embodiment, the switching device is placed so that the heater (or other electrical load) is at a positive potential with respect to ground even when the switching device is off, and a ground fault indicator is used to compare the currents in the two legs of the circuit and to signal when a ground fault causes the currents to differ.

Abstract: A current detecting device includes high frequency oscillation detecting circuits which, when a saturable reactor oscillates at a high frequency, detect the high frequency oscillation of the reactor and generate a high level output. Thus, when a large current flows through the reactor and the magnetization characteristic of the reactor is varied to generate a normal detection output, the reactor oscillation due to the large current is detected and an operating circuit for driving an external device is energized.

Abstract: With most fluorescent lighting fixtures, the voltages required at the sockets to start the fluorescent lamps are so high as potentially to constitute a substantial electric shock hazard to persons having to service such fixtures. To mitigate this hazard, whenever socket voltages exceed certain levels, protective measures have to be provided.The essential shock hazard problem associated with a fluorescent lighting fixture relates to the situation where a person, who may be in contact with earth ground, is holding onto one end of a fluorescent lamp while the other end of the lamp is inserted into its socket.In its preferred embodiment, subject invention constitutes an electronic ballasting means for fluorescent lamps, with said ballasting means comprising an inverter operating at a frequency of about 33 kHz.

Abstract: The invention relates to a circuit breaker for cutting off the two AC supply leads of an electrical receiver from the time of creation of a leakage current F between said receiver and ground through a human body. This circuit breaker comprises a differential transformer generating a faulty voltage V.sub.O, a relay with contacts open when it is not energized, and means (A.sub.1,A.sub.2, . . . A.sub.n ; R.sub.1,R.sub.2 . . . R.sub.n) supplied by the system, adapted to exploit the voltage V.sub.O for the purposes of energizing the relay if the current F is dangerous or at least unpleasant in its intensity and/or its duration, without however being sensitive to disturbances.

Abstract: An integrated circuit ground fault signal processor utilizes a power supply having a first, regulated, half-wave rectified supply voltage section and second DC supply voltage section. Operating current for a fault signal amplifier and charging current for a fault signal integrating capacitor are drawn from the second power supply section on a full-cycle basis. Operating current for a trip threshold detector or comparator and a high frequency oscillator circuit is drawn from the first power supply section for operation on an alternate half-cycle basis.

Abstract: An electricity meter for metering the amount of electrical energy supplied by a power supplier to a power consumer is provided with fraud detection means for detecting the presence of an external shunt which has been connected to by-pass its internal current sensing means. The detection means, which comprises a differential current sensor for sensing the difference between the respective currents flowing to and from the consumer via the meter and a multiplier for multiplying this current difference by a signal derived from the supply voltage, is arranged to operate a circuit breaker, and/or to compensate the energy measurement of the meter, and/or to provide a warning to the supplier. The differential current sensor also senses when current is being taken between the live wire and earth on the consumer's side of the meter.

Abstract: A protection device has first and second differential transformers each with a toroidal magnetic core through which pass the neutral and phase conductors of an alternating current distribution network, and a secondary winding. The secondary winding of the first transformer is coupled to the input of an amplifier followed by a rectifier, a threshold comparator and a control device adapted to release a circuit-breaker. The secondary winding of the second transformer is coupled to the output of the amplifier. The improvement is constituted by an auxiliary amplifier inserted between the output of the first amplifier and the terminals of the secondary winding of the second differential transformer.

Abstract: A ground fault circuit breaker including ground fault interruption means and overload interruption means that are independently responsive to open a common set of breaker contacts upon respective ground fault and overload conditions is provided with a trip indicator visible external to the breaker that operates on actuation of the ground fault interruption means but not upon operation of the overload interruption means, the trip indicator being a mechanical device that is actuated upon the movement of the solenoid plunger that operates upon occurrence of a ground fault condition.

Abstract: A ground fault interrupter employs a single differential transformer that is made of a ferrite toroid with an eleven turn secondary winding. The transistorized fault detector circuit is for the most part formed on a silicon integrated chip. The hot-wire-to-ground-fault detector portion is an impedance-transforming circuit that when energized presents a low impedance, i.e. virtually a short circuit, to the secondary winding. A multiplexing circuit periodically de-energizes the hot-wire-to-ground-fault detector causing it to present a high input impedance during periods when neutral-wire-to-ground faults are sensed via the transformer.

Abstract: A plurality of relatively high magnetic permeability strips are interleaved to form layers of a closed loop differential transformer core. Although the material of each layer by itself may have a relatively square hysteresis loop, the core formed of a plurality of interleaved layers of such material has a substantially more rounded hysteresis loop. Such a core can advantageously be used in a ground fault interruption circuit in which power leads pass through a central opening in the core to form a primary winding and a secondary winding wound on the core may have a capacitor connected in circuit therewith to complete a resonant circuit.

Abstract: A ground fault interrupter (GFI) circuit for interrupting alternating current delivered in a power distribution system whenever a ground fault current exceeding a prescribed level is sensed. The GFI circuit includes a differential current sensing apparatus for sensing the presence of a ground fault current and generating a control signal that assumes a first condition whenever the ground fault current exceeds the prescribed level and for assuming a second condition whenever the ground fault current is less than the prescribed level. A charging circuit is charged with an electrical charge during a fixed portion of each cycle of the alternating current if the control signal has assumed the first condition. If the control signal has assumed the second condition, the charging circuit is discharged during a fixed portion of each cycle of the alternating current, thereby preventing any substantial charge from being stored in the charging circuit.

Abstract: In an integrated circuit for a ground fault circuit interrupting device, a power supply voltage regulator is utilized to turn on a double grounded neutral excitation oscillator and to inhibit trip initiating thyristor triggering while the half-wave rectified supply voltage is in regulation and, as the supply voltage goes into regulation near the beginning of each alternate half-cycle, condition a comparator to issue a thyristor triggering pulse if an integrated fault signal voltage has achieved an established trip threshold level.

Abstract: A fault signal integrating capacitor and a comparator responsive to an integrated fault signal voltage are connected in feedback circuit fashion such as to provide for the generation of a succession of thyristor gate triggering pulses to insure reliable current activation of a trip solenoid acting to effect separation of circuit interrupting contacts.

Abstract: A ground fault circuit breaker including ground fault interruption means and overload interruption means that are independently responsive to open a common set of breaker contacts upon respective ground fault and overload conditions with a trip indicator visible external to the breaker that operates on actuation of the ground fault interruption means but not upon operation of the overload interruption means with means for electrically actuating the trip indicator upon occurrence of a ground fault condition that actuates the ground fault interruption means.

Abstract: A zero-phase current transformer for use as a leakage current detecting element in a leakage current interrupter in which two magnetic materials of different permeabilities are provided so as to eliminate a range where the leakage current interrupter is inoperable without lowering its ability to distinguish noise components. The different magnetic materials may be provided as a single core constructed by mixing the materials of different permeabilities. Otherwise, the materials can be provided as annually-shaped magnetic pieces stacked one on top of the other. Still further, the materials of different magnetic permeability may be provided as bands of materials interwound to form alternating layers or one of the materials may be provided as at least a portion of a protective case.

Abstract: For use in D-C power transmission systems there is provided a circuit breaker system which is responsive to leakage currents to ground to break the circuit from the power source to the D-C transmission lines. A toroidal saturable core surrounds the D-C transmission line feed conductors and carries on such core a primary and a secondary transformer winding. An A-C source is connected to the primary winding in series with one of two field coils in the electromagnetic circuit of an electromagnetically actuated circuit breaker. The other field coil in the electromagnetic circuit of the breaker is connected to the secondary winding on the saturable core.

Abstract: An earth leakage protection device comprises a core balance current sensing transformer 1 having a secondary winding 2 in which a fault signal is generated in response to leakage from AC supply lines forming primary windings of the transformer 1, an operational amplifier OA1 for amplifying the fault signal, a precision rectifier circuit 8 comprising a pair of operational amplifiers OA2 and OA3 for performing full wave rectification of the amplified fault signal, a delay circuit 9 in the form of a two stage RC network which delays the rectified signal according to an IDMT characteristic, and a trigger circuit 10 in which the delayed signal is compared with a preset reference signal by an operational amplifier OA4 to provide a control signal which actuates a sagety device in the AC supply lines via a relay 11 when the reference signal is exceeded.

Abstract: An electric current detector circuit for sensing a leakage of electrical current in a particular system and then providing a signal to control the operation of the system. The circuit is also adapted to receive a signal upon the occurrence of fire, in and around the system attached thereto, and then provide a signal to further control the operation of the system.

Abstract: For optimizing the manufacturing cost of the magnetic torus of a differential transformer, the volume is reduced in that the free volume of the central aperture is fully filled: only one turn for each primary conductor, the section of which is reduced, the adjacent parts of larger section forming heat sinks, the central part of the conductors having the form of circular sectors. An important saving is secured on the most expensive part of the relay.

Abstract: The device detects variations in magnetic flux so that the passage through a given threshold by the amplitude of such a variation per unit time is manifested by the movement of an element adapted to trigger an action.

Abstract: A ground fault circuit interruption device including a standard molding case circuit breaker and a molded case ground fault detector module mounted in side-by-side relationship. The ground fault detector module includes a push button test switch which is open in the uppermost and in the lowermost positions. Flexible conductors extend through openings provided in the wall of the ground fault detector module and are connected to the line terminals of the circuit breaker. A reset push button is positively latched in the reset position.

Abstract: A device for sensing current flow in an electric conductor employs a ferromagnetic core coupled to the conductor and a control winding on the core for applying a periodic magnetic flux to a part of the core of a magnitude to vary the core permeability, preferably driving a part of the core in and out of saturation. The periodic flux interrupts any flux circulating in the core due to current flow in the conductor. An output winding on the core has a signal voltage induced therein whose amplitude is determined by the rate of change of the interrupted circulating flux. The device effectively amplifies a small current input signal to a relatively high output level. A bias winding may be wound on the core to compensate for stray magnetic fields in the vicinity of the device.

Abstract: A line current measuring arrangement employs two separate toroidal cores with line windings and control windings. The line windings cause equal amounts of the same polarity of magnetizing intensity H in the cores when a line current flows. The control windings are pulsed by control signals to cause equal changes of opposite polarity of control H in the two cores to drive the two cores to opposite polarities of saturation of magnetic induction B. The same control windings also provide a succession of voltage pulses where the amplitudes and polarities of the pulses are measures of differences in the changes of B in the two cores. A succession of voltage pulses is cumulatively and algebraically integrated to provide a changing output voltage which is a measure of the cumulative integration. The output voltage is effective through the agency of the same control windings to cause feedback H in both cores in opposition to any line H.

Abstract: A line current measuring arrangement employs two matched toroidal cores with line windings, control windings, sense windings, and feedback windings. The line windings cause equal amounts of the same polarity of magnetizing intensity H in the two cores when a line current flows. The control windings are pulsed by control current pulses to cause equal changes of opposite polarity of control H in the two cores to drive the two cores to saturation of magnetic induction B. The sense windings are serially opposed so that the changes of B in the two cores cause sense voltages in polarity opposition. Any difference in the sense voltages, due to the presence of line current H, is cumulatively and algebraically integrated to provide a changing output voltage which is a measure of the cumulative integration. The output voltage causes feedback H in both cores in opposition to any line H.

Abstract: In an electronic module for a ground fault interrupter the portion that amplifies a sensed ground fault signal is in the form of a series of cascaded CMOS inverter stages. The electronic module also includes an additional CMOS inverter providing a balanced input to the amplifier to aid in preventing operation of the ground fault interrupter during the turn-on period of operation.

Abstract: An electric receptacle for trade size outlet boxes having a ground fault circuit interrupting mechanism incorporated therein. A receptacle housing includes contact jaws seated therein to receive the plug of a conductor leading to a load, electronic components to detect a ground fault and grounded neutral condition on the load side of the receptacle, plus a coil and trip mechanism to open the receptacle circuit on occurrence of a ground fault or grounded neutral condition. The complete receptacle assembly is approximately the same depth as conventional household receptacles which do not have ground fault circuit interrupting means included therein. Means to periodically test the ground fault interrupting mechanism is also included in the receptacle assembly, as well as means to indicate the circuit has been interrupted and means to reset.

Abstract: A ground fault interruptor comprising a reed relay connected to the secondary of a differential transformer, a load connected to the primary windings of said transformer through the contacts of a relay or circuit breaker, a power supply circuit for said relay or circuit breaker, a biasing circuit connected to said reed relay and a signal processing circuit for processing the signal from the secondary of said transformer to said reed relay.

Abstract: A ground fault circuit breaker is provided which includes means for sensing ground fault current and for analyzing the waveform of the ground fault current. An operating mechanism automatically separates the contacts of the circuit breaker upon detection of ground fault current waveforms corresponding to the waveform of current passing through human skin. In a preferred embodiment, means are provided to synchronously detect the third harmonic component of ground fault current using phase and amplitude information to determine the presence of a ground fault path through human skin. Alternatively, means are provided to sense peak and average values of ground fault current and to trip the breaker whenever the ratio of peak to average ground fault current exceeds a predetermined level. In another alternative, the slope of the ground fault current at zero crossing is detected and compared to the ground fault current peaks.

Abstract: A sensed current resulting from the occurrence of a ground fault is amplified by a differential amplifier and applied to a waveform shaper after having been delayed. The waveform shaper includes two complementary transistors interconnected into a thyristor and a transistor for amplifying the delayed current from the thyristor to a constant current under the control of a negative feedback transistor. The constant current is applied to a thyristor to turn it on to activate an associated circuit interrupter.

Abstract: In the absence of a ground fault, a triac completes an AC energization circuit for a relay whose contacts then close to provide load circuit continuity. Gate drive for the first triac is obtained from a secondary winding of a transformer whose primary is driven by an oscillator for the purpose of producing a differential transformer unbalancing current signal in the event of a desensitizing ground fault on the load circuit neutral conductor. When the differential transformer senses a ground fault, the oscillator is disabled, and the resulting loss of gate drive renders the triac non-conductive to drop out the relay.

Abstract: A ground fault interrupter for two and three wire, single phase load circuits employing a circuit breaker having an electro-responsive contact trip-open mechanism, a fault sensing differential transformer, an operational amplifier providing characteristic output pulses whose magnitude depends upon the non-presence or presence of a ground fault and whether the latter is resistive or reactive in kind, and an energizing circuit for the electro-responsive contact trip-open mechanism including a transistor which is normally held non-conducting in the absence of a ground fault and rendered conducting whenever a resistive ground fault occurs. A capacitor in circuit with the amplifier output and transistor base renders the transistor immune from amplifier pulses characteristic of reactive ground faults. Varistors are included between the load circuit wires to suppress transient voltage surges from falsely inducing nuisance ground fault interrupting action.

Abstract: A sensor develops a ground fault signal in response to a ground fault on a power distribution circuit, which signal is processed by a signal processor of a conventional, residential ground fault circuit interrupter (GFCI) pursuant to developing a trip signal resulting in energization of a light emitting device. The light signal emitted by this device triggers a solid state, light activated switch to complete an energization circuit for a solenoid acting to shunt trip a power circuit breaker operating to interrupt the distribution circuit.

Abstract: A ground leakage current interrupter circuit including a transformer having a pair of balanced differential primary windings and a secondary winding, a fault detector for monitoring the output of the secondary winding and producing a fault signal in response to increases in the level of the secondary winding output that occur at greater than a predetermined rate, and a circuit interrupter responsive to the fault signal produced by the fault detector. Preferably, the fault detector includes a level detector for producing the fault signal in response to secondary winding output levels greater than a reference signal level, and a reference supply that varies the reference signal level in dependence upon the level of the secondary winding output so as to prevent production of a fault signal in response to increases in the secondary winding output that occur at less than the predetermined rate.

Abstract: A ground fault circuit interrupter which utilizes one trip coil to perform the combined functions of interrupting a circuit on occurrence of a ground fault as well as an under voltage condition. An electronic module supplies continuous current to the trip coil until a ground fault or under voltage condition occurs. The armature is spring biased in a direction away from the trip coil, with tension of the spring adjusted to pull the armature away from the trip coil when voltage in the coil decreases below a selected amplitude.

Abstract: A ground fault protector includes a conventional ground fault circuit interrupter (GFCI) electronic module which receives operating power over a separate supply circuit to render the protector operable in affording personnel ground fault protection for a circuit whose nominal voltage is inappropriate to power the module. The protector includes contacts operating in both the supply and protected circuits such that, in the event of a ground fault on the protected circuit, both circuits are interrupted. The supply circuit is also equipped to simulate a ground fault condition for verifying operability of the protector.

Abstract: A ground fault circuit interrupter includes a differential current transformer sensing winding supplying input to an integrator which is reset to zero at the end of each half-cycle of AC line current. A line-to-ground fault current will cause the integrator output to exceed a predetermined limit value and produce a trip indication. A saturable neutral transformer supplies a voltage to the neutral line and a reference current proportional to the neutral voltage to a comparator. The peak value of the reference current is compared to the peak value of the sensing winding output. A low-resistance neutral-to-ground path causes the sensing winding output to exceed the reference current and a signal to be added to the integrator input, thereby producing a trip indication which energizes an SCR to activate a solenoid.

Abstract: A ground fault and fire detector system for an A.C. electrical power distribution apparatus including a multi-pole circuit interrupter to disconnect a poly-phase electrical power supply from a load. A single-pole circuit device is operatively connected to the circuit interrupter for controlling its operation. Ground fault sensing circuitry is operatively positioned with respect to at least one wire for initiating a fault current. The single-pole circuit device is responsive to the fault current for activating the circuit interrupter to disconnect the power supply from the load.

Abstract: A circuit for detecting line-to-ground and neutral-to-ground faults and in response thereto interrupting the line conductor. Included in the circuit is a magnetic core about which the neutral conductor and line conductor are wound to produce a zero net magnetomotive force in the core in the absence of a line fault and a non-zero net magnetomotive force in the presence of a line fault. A secondary winding wound on the core has at least one diode or thermistor connected thereacross. The diode or thermistor has a dynamic impedance, which is reflected back to the neutral winding, which decreases when current flows through the diode or temperature rises in the thermistor in response to an induced voltage in the secondary winding caused by non-zero net magnetomotive force in the core produced by a current imbalance in the line and neutral conductors due to a line fault.

Abstract: In order to prevent excessive voltages originating in customer owned terminal equipment from creating a hazardous condition in an associated telephone line, a protective circuit is connected between the equipment and the line. This circuit responds to an unbalanced current flow by disconnecting the equipment from the line and providing a local path to ground for the current. The circuit remains activated as long as the unbalanced current flow continues and reconnects the equipment to the line only when the current flow ceases.

Abstract: A single transformer is alternately operated as a differential current transformer with its secondary winding connected as the input to a low impedance differential amplifier with large negative feedback during a ground fault current sampling period and then as a coupled resonant circuit operating into a negative resistance network during a neutral-to-ground resistance sampling period. During the fault current sampling period, the amplifier is gated ON and OFF to switch the transformer secondary loading between essentially short-circuit and open-circuit conditions. The resulting amplifier feedback current pulses, indicative of transformer secondary current, are integrated either directly or indirectly, to develop a DC signal proportional to any ground fault current.

Abstract: Ground fault protective systems are disclosed in which fault signals are generated in response to differential currents carried by electrical supply lines. A circuit breaker interrupts power on the supply lines when the fault signals exceed a given magnitude and duration. Downstream reactances to ground from one or more supply lines give rise to spurious fault signals which do not characterize true ground fault conditions. These spurious fault signals are cancelled prior to detection by means of neutralizing auxiliary circuits. The resulting fault signals exhibit a high signal-to-noise ratio.

Abstract: A fault current protection switch detects fault currents from conductors of a supply means to ground. The system uses at least one difference transformer connected to the conductors of the supply mains. An oscillation generator circuit is connected to the difference transformer through feedback windings. The oscillation generator circuit checks the magnetization of a core of the difference transformer, and, in the event of a change in the transforming properties of the core due to "mis" magnetization caused by a fault current, the oscillation generator circuit triggers a control and switching member connected in the supply mains to disconnect the same.

Abstract: An electromagnetic sensing apparatus includes one or more magnetic cores coupled by windings to a pair of transmission line conductors for sensing the presence, and in some cases the magnitude and direction of loop currents flowing in the transmission line, without interfering with the transmission of signal information therealong. In one embodiment, the direction of loop current flow in the transmission line conductors is detected by applying a steady-state electromagnetic bias to the magnetic core to cause a polarity or direction determining asymmetrical response in a sense circuit that is electromagnetically coupled to the core by a sense winding. In another embodiment, a pair of separate magnetic cores are used, each having associated drive windings connected in series with the transmission line conductors, and associated sense windings.

Abstract: Telephone terminal equipments connected to the network through the device described herein are prevented from applying potentially human-hazardous voltages or currents to the network. The device includes a pair of bifilar relay coils, one in each connection to the central office. These operate an associated relay contact only when an unbalanced voltage or current condition occurs on the customer leads. A circuit path is thus completed to operate a second relay, which opens the connection between the customer terminal leads and the network leads; and establishes a path to ground through its own coils for the current from the unbalanced source. Means are included for assuring that the fraction of hazardous voltage appearing across the second relay remains essentially constant in the frequency range of 17 to 60 hertz. Only removal of the unbalanced current can release the relay and restore the network connection.

Abstract: This invention relates to an arrangement of contact potential responsive switching devices.According to this invention the contact voltage responsive switch and the outlet may either be combined into a unit, or the switch and an outlet may be arranged at different locations, or the switch may be combined with the outlet into a unit, and one or more outlets positioned at different locations all of which are controlled by the switch may be added.

Abstract: A ground leakage relay circuit including a core balance transformer through which pass the supply and return line of the circuit to be protected and having a multi-turn secondary winding. A capacitor is connected to be normally charged from a d.c. source. A normally conducting transistor is connected across the capacitor. When the transformer secondary winding exceeds a preselected level, the transistor is switched "off" to permit a voltage build-up across the capacitor. When the voltage across the capacitor reaches a triggering value, it actuates a relay to open the supply line.

Abstract: An electric receptacle for ordinary household or trade size junction boxes having a complete ground fault circuit interrupter incorporated in the receptacle, including electronic components to detect a ground fault on the load side of such receptacle, and a coil and trip mechanism which is actuated when a ground fault is detected. On occurrence of a ground fault, the coil and trip mechanism opens the protected circuit. Means to test the interrupting mechanism, means to indicate the interrupter contacts are open, means to reset after testing or occurrence of a ground fault, and means to provide an audible signal if improperly wired, are included.

Abstract: Ground fault circuit breaker structure characterized by an insulating integral housing having a pair of side-by-side compartments that are separated by a partition wall. A circuit breaker is located in one compartment and a ground fault detector is located in the other compartment and isolated from the circuit breaker. The ground fault detector comprises a differential transformer comprising a current monitoring core, a plurality of primary windings on the core, each being one of a line and a neutral conductor of an A.C. electrical distribution system, a secondary winding sensing current unbalance between the primary windings, means responsive to a predetermined sensing signal to open the line conductor; and the line conductor extending between the circuit breaker trip means and through aperture means in the partition wall and through the magnetic core and back through the aperture means to the load terminal.

Abstract: A ground fault circuit interrupter comprises separable contacts for interrupting current flow through a power circuit being protected, trip means operable upon energization to effect separation of the contacts, means for detecting ground fault current, means for monitoring voltage upon the power circuit, and means responsive to the ground fault current detecting means and the voltage monitoring means for energizing the trip means when ground fault current reaches a trip current level. The trip current level varies as a function of the power circuit voltage.

Abstract: A ground fault and fire detector system for an A.C. electrical power distribution apparatus including a multi-pole circuit interrupter to disconnect a poly-phase electrical power supply from a load. A single-pole circuit device is operatively connected to the circuit interrupter for controlling its operation. Ground fault sensing circuitry is operatively positioned with respect to at least one wire for initiating a fault current. The single-pole circuit device is responsive to the fault current for activating the circuit interrupter to disconnect the power supply from the load.