Abstract: A trip device comprising a differential current detection transformer, a trip relay of a breaking mechanism of the circuit breaker and a test circuit for checking the operation of the trip device. The relay comprises a fixed yoke bearing a coil and a blade that is mobile with respect to the yoke. During normal operation of the trip device, the blade is held magnetically in the position pressing against the yoke and when a differential current occurs, the blade actuates the breaking mechanism. The test circuit generates a vibration of the blade, without causing tripping of the mechanism, in order to check its ability to disengage from the fixed yoke. Advantageously, this vibration is obtained by application of a voltage in the form of pulses to the terminals of the coil.

Abstract: A ground fault circuit breaker includes separable contacts for interrupting current flow in a protected AC electric system when opened. The protected AC electric system includes a ground fault switch, such as a ground fault receptacle having a people protection ground fault trip curve, downstream from the ground fault circuit breaker. A current transformer generates an AC sensor signal representative of AC current flowing from the protected AC electric system to ground. A ground fault controller, connected to the current transformer, generates a ground fault trip signal as a function of the AC sensor signal and an equipment protection ground fault trip curve. A trip means, which is responsive to the ground fault trip signal, opens the separable contacts.

Abstract: A differential protection device includes a current transformer comprising a toroid formed by a magnetic core, primary windings formed by the active conductors of the installation and a secondary winding at the terminals of which a differential fault signal is established when a differential fault occurs in the primary windings, a tripping relay of a current breaking apparatus, and a secondary connection circuit connecting the relay to the terminals of the secondary winding, the secondary connection circuit being arranged to bring about tripping when the signal exceeds a preset threshold. The above-mentioned secondary circuit comprises a full-wave rectifier and a capacitor, connected in parallel with the secondary winding of the toroid, and the magnetic core is made of a nanocrystalline material.

Abstract: An arrangement for transmitting electric power from a source point to a load point comprises (i) a first sensor to monitor the amount of power being supplied from the source point, (ii) a second sensor to monitor the amount of power being received by the load point, and (iii) communication circuit for communicating to a control circuit information in respect to the amount of power supplied from the source point as well as that received by the load point. The control circuit then compares the amount of power supplied versus that received, and provides a warning and/or halts the supply of power in case a substantive discrepancy were to occur between power supplied versus power received. Thus, in case an improper loading were to occur between the source point and the load point, it would be detected by the control circuit, which would then instigate protective action.

Abstract: A modular leakage current detector and machine interrupter including a sense module for detecting ground fault currents in excess of a given value, the sense module including circuitry to provide an interrupt signal, a circuit interrupter interconnected to the sense module to disconnect power to the machine upon receipt of the interrupt signal, and a test and control module electrically connected to the sense module, the test and control module providing a fault signal to periodically test the operability of and reset the modular leakage current detector and machine interrupter.

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: An arc fault detector embodied as both a stand alone device and in combination with a circuit interrupting device such as a ground fault circuit interrupter (GFCI) functions to provide protection from potentially dangerous arc fault conditions. The device utilizes line side and load side pickup coils to permit distinguishing between arc faults occurring on the line side and the load side of the device. The arc fault circuit interrupter (AFCI) circuitry portion of the device shares components from the GFCI circuitry portion as an integral part of its functionality. The AFCI utilizes the electromechanical power carrying, portion of the GFCI, including the AC line disconnect circuitry, the power supply and the physical housing. In addition, the AFCI employs quantitative detection using variable gain control in combination with either a load disconnect or audible/visual alarm indication.

Abstract: An earth-leakage circuit breaker has a totalizing current transformer, a magnetic trip device and switchgear with main current contacts for the main leads. A current-signal generator, a current sensor, a time-signal generator and an electronic timer wherein the switching value and response time of the circuit breaker are measured at predetermined intervals, compared with reference switching values and response times and, if these reference values are exceeded, an alarm is promptly given. During the measurement, a locking device prevents the main current contacts from opening and/or when predetermined limiting switching and response times are exceeded, the locking device opens the main current contacts and subsequently acts as a lock preventing the contacts from closing again, which is equivalent to fail-safe behavior. In addition, the switching value of the circuit breaker is multiplied by its response time and the product, which may exceed a particular constant value, is used for monitoring purposes.

Abstract: A ground fault circuit interrupter comprises a transformer having a saturable core; a secondary winding on the core; an integrating detector coupled to the secondary winding; and a pulse stretcher connected between the secondary winding and the differential detector for stretching high voltage short duration pulses sufficiently to allow them to be detected by the detector.

Abstract: A miniature appliance leakage current interrupter (ALCI) interrupts the flow of current through a pair of lines extending between a source of power and a load. The ALCI comprises a circuit breaker having a pair of normally closed switches, one switch being located in each of the pair of lines between the source of power and the load. The circuit breaker is connected to a relay circuit which selectively opens the pair of normally closed switches. The relay circuit is connected to a fault detection circuit which detects the presence of a ground fault condition in the pair of lines. When the ground fault condition detected exceeds a predetermined value, an integrated circuit chip in the fault detection circuit causes the relay circuit to open the circuit breaker. The ALCI further includes a single-sided circuit board which is housed within a generally rectangular plug. The circuit board has a first side and a second side, the second side having a pattern of conductive paths.

Abstract: A ground fault protection module is attached to a circuit breaker employing a thermal-magnetic trip unit to separate the circuit breaker contacts upon occurrence of a ground fault. The ground fault module contains a logic circuit and a giant magnetic resistor for detecting the ground fault.

Abstract: A multi-pole circuit breaker assembly for interrupting AC power to a load upon the detection of an earth leakage fault or an overcurrent condition includes a pair of circuit breaker units mounted adjacent to an earth leakage module. The earth leakage module includes an electronic circuit that senses a current imbalance between the power line lead and the neutral line lead using a differential transformer. In response to a current imbalance greater than a predetermined value, the electronic circuit periodically energizes a switching circuit that provides power across a solenoid. The solenoid, when actuated, engages a common trip mechanism to open concurrently the contacts of the circuit breakers units. The common trip mechanism includes an elongated bar that extends through the casing of the earth leakage module and the circuit breaker units. The elongated bar engages a U-shaped trip member pivotally disposed in each circuit breaker.

Abstract: Fault-current protector circuitry has a first totalling current transformer (7) with a primary winding formed from phase (1) and neutral (2) conductor lines and a secondary winding (13) connected to a first analyzer circuit (16). A second totalling current transformer (10) has a primary winding formed by a protective conductor line (3) and a secondary winding (17) connected to a second analyzer circuit (20). A trigger device (24) connected to the first and second analyzer circuits actuates switches (4,5,6) which are connected into each conductor (1,2,3). The fault-current protector circuitry is especially for isolation monitoring of electrical circuits and which has the advantage of reliably isolating the monitored circuit from the mains if fault currents occur in the phase or neutral conductor lines and if a current appears in the protective conductor line.

Abstract: In an electrical power supply system provided with a step-down distribution transformer connected to a power source to supply current to at least one neutral grounded load center, said power source having a conductor connected to a first primary grounding connection, said distribution transformer having a magnetic core, and a primary and a secondary winding independently mounted on said magnetic core, said secondary winding being electrically connected to a pair of output terminals and to a center-tapped neutral terminal, said terminals being connected to said load center, said primary winding being electrically connected to a pair of input terminals arranged for connection to said primary power source, one of said input terminals being further connected to a second primary grounding connection, said center-tapped neutral terminal being connected to said second primary grounding connection via a shunting conductor, an improvement comprising a current balancing transformer (CBT) having a magnetic core and a fi

Abstract: A multiwire branch circuit including two line conductors and a grounded, common neutral conductor is protected by a two pole circuit breaker connected to interrupt current flow in the two ungrounded line conductors. Three separate protection circuits provide arc fault protection for each of the ungrounded line conductors and ground fault protection for all three conductors. The arc fault detectors use the bimetal of the thermal-magnetic trip device for the associated line conductor, and therefore, are individually referenced to the associated line voltage. Hence, the outputs of the arc fault detectors are electrically isolated from each other and from the output of the ground fault detector, but operate a common trip circuit to open the two pole circuit breaker. The arc fault detectors have separate isolated power supplies. The ground fault detector is powered by a supply which is energized if either of the ungrounded line conductors is energized.

Abstract: A Positive Temperature Coefficient Resistivity (PTC) element has a resistivity that increases as the temperature increases. Circuit breakers having PTC elements can achieve better overload and short circuit protection than existing products. Breakers with PTC elements can also be combined with ground fault detection circuits to activate the circuit breaker under ground fault conditions that are less severe than the overcurrent conditions that would normally activate the circuit breaker. A shunt trip assembly incorporating a PTC resistor reduces the required power rating of the clearing switch.

Abstract: A circuit for driving a load. In one embodiment, the load is driven by an inverter circuit having a full bridge circuit divided by inductive elements to provide cross conduction protection. In another embodiment, first and second converter circuits are coupled to the inverter circuit with the inverter and converter circuits having common circuit elements. In a further embodiment, a common mode inductor is inductively coupled to a power circuit for detecting a common mode signal generated by a load current return path disruption. The common mode inductor is coupled to a control circuit for limiting current to the load.

Abstract: An in-line cord ground fault circuit interrupter which contains within a common housing the sensing unit and the tripping relay usually found separately packaged at a remote location. The fixed contacts are mounted on fixed contact arms mounted adjacent one surface of a printed circuit board with the movable contacts mounted on movable contact arms mounted adjacent the second surface. The tripping relay operates an armature between an open and a closed condition and by cams on the arms of the armature opens and closes the movable contacts with the fixed contacts. The two portion housing allows the components of the interrupter to be mounted on one portion of the housing which also supports the line and load conductors making assembly of the rear housing portion to the front housing portion easy. A stop member and a positioning post are provided on the interior of the front cover to check the position of the armature in the non-energized state to verify proper contact placement and gaps.

Abstract: A leakage current interrupter comprising a trip mechanism that operates automatically in response to the presence of a shock hazard condition. Actuation of the trip mechanism automatically interrupts the flow of current to a load and permits movement of a reset button to take place to visually signal that current to the load has been interrupted, although interruption of current flow is not in any way dependent on movement of the reset button, whereupon if movement of the reset button is prevented for any reason, the flow of current to the load is still automatically and instantaneously interrupted in response to the presence of a shock hazard. Such shock hazard exists when two separated shock hazard conductors in said load are bridged by a conductive material, such as water.

Abstract: A ground fault circuit interrupt system with auxiliary surge suppression ability is provided which includes line-side system, phase, neutral and ground terminals electrically connectable to phase, neutral and ground terminals of an AC source and load-side system, phase, neutral and ground terminals electrically connectable, respectively, to phase, neutral and ground terminals of an electrical load. The system includes a ground fault circuit interrupter including line- and load-side phase and neutral ports for electrical connection to the line-side system, phase and neutral terminals for controlling a state of conduction of AC between the source and electrical load in accordance with a detection of an interrupt condition.

Abstract: Arcing-faults in an electric power distribution system are detected by a circuit which includes a band-pass filter generating a low frequency bandwidth limited arcing current signal having a bandwidth above the measurable harmonics of the ac current but below the frequency band of power line communications systems, about 3 KHz to 20 KHz and preferably about 6 KHz to 12 KHz. For each cycle of the ac current that this low frequency bandwidth limited arcing current exceeds a threshold, preferably related to the amplitude of the ac current, for a selected duration of the cycle, a fixed pulse is generated. If a time attenuated accumulation of these fixed pulses reaches a selected level representative of a number of closely spaced cycles in which the arcing current has been detected for the selected duration, an arc indicative signal is output.

Abstract: A resettable ground fault circuit interrupter most advantageously suited for use with 400-Hz aircraft electrical systems and designed to interrupt the AC power between an aircraft electrical system and one or more electrical appliances being operated therein when a ground fault occurs. The circuit relies upon an imbalance sensor which is implemented in the preferred embodiment disclosed herein as a multi-turn coil of a transformer through which input wires connected to an AC input terminal are threaded so that an imbalance resulting from a ground fault can be detected by the coil. The signal generated by the coil as a result of such an imbalance is then amplified and applied to a thyristor, the conducting or non-conducting state of which determines whether or not the circuit is in a configuration for interrupting the AC signal or not interrupting the AC signal. Light emitting diodes are utilized to indicate the interruption status of the circuit.

Abstract: A ground fault circuit interrupt system with uncommitted contacts is provided which includes line-side system, phase, neutral and ground terminals electrically connectable to phase, neutral and ground terminals of an AC power source and load-side system, phase, neutral and ground terminals electrically connectable, respectively, to phase, neutral and ground terminals of an electrical load. The system includes a ground fault circuit interrupter including line- and load-side phase and neutral terminals for electrical connection to the line-side system, phase and neutral terminals for controlling a state of conduction of AC current between the source and electrical load in accordance with a detection of an interrupt condition.

Abstract: A current differential protection arrangement for an electric power supply unit with a measured value pre-processing device and an analysis device that checks on the basis of a predefined dependence of a differential current on a stabilizing current (response characteristic curve) to determine whether the differential and stabilizing current values thus formed are in a blocking range or a triggering range, where an additional stabilization range is present in the blocking range. To avoid fixed-time blocking after an external fault with transformer saturation with such a protection arrangement, the analysis device in a stabilizing circuit contains a testing arrangement which checks the current values thus formed to determine whether they describe a point in the additional stabilization range. If this is the case, a blocking signal is produced, which activates the blocking device downstream from the testing arrangement.

Abstract: A dual trip level ground fault interrupter (GFI) which is designed to trip or operate at a first relatively low personnel protection level of ground leakage current, and also at a second relatively high equipment protection level of grounded leakage current. The dual trip level ground fault interrupter is provided for a power line, having line conductors and a ground conductor, supplying electrical power to a load. The dual trip level GFI comprises first and second differential current transformers, each having a primary winding and a secondary winding. All of the line conductors for the load pass through the primary winding of the first differential current transformer. All of the line conductors and the ground conductor pass through the primary winding of the second differential transformer. The ground conductor does not pass through the primary winding of the first differential current transformer.

Abstract: A coaxial drop cable safety device is used for cable television, data and telephony applications. The device is used on buried drop cable where 60 Hz powering voltages applied to the drop cable exceed low voltage safety limits and where the drop cable is buried at depths which is less than the minimum required to meet electrical safety codes. Tap end and premise end units are connected to the drop cable. The tap end unit applies a DC voltage to the center conductor of the drop cable. A monitoring circuit in the tap end unit monitors the center conductor DC voltage to a fault from the center conductor to ground along the drop cable. The tap unit will immediately remove the powering voltage In the event of either an open or faulted condition on the center conductor along the entire length of the drop cable.

Abstract: A ground fault protection circuit for plural loads connected across a power source with plural branches which can be used where the loads are unbalanced. Each branch includes a ground fault circuit interrupter device that has a common line for the electronics of the GFCI separate from the neutral line from the power source to the load where the common lines for the electronics for the ground circuit interrupter devices in each branch are connected to a common point. The ground fault protection circuit employs plural ground fault circuit interrupter devices and eliminates nuisance tripping. The common line for the electronics for a GFCI is routed through the core of the current sensing transformer of the GFCI. The separate neutral line for the electronics, connecting the common lines for the electronics for plural GFCI devices and routing the common lines for the GFCI electronics through the core of the transformer of each GFCI, eliminate improper GFCI operation due to unbalanced loading.

Abstract: An electrical protection system which uses a ground fault interrupter (GFI) to protect a circuit from (A) ground faults and (B) overcurrents and/or overvoltages. For overcurrent protection, a control element may be coupled in series with the line or return input to the GFI, and a bypass element may be coupled in parallel with the control element and the GFI. In case of an overcurrent, the control element causes current to be diverted through the bypass element, thereby creating a current imbalance in the GFI circuitry causing the GFI to open the circuit. For overvoltage protection, a bypass element (e.g. a varistor) may be coupled between, e.g., the line sense input of the GFI and the return sense input of the GFI. In case of an overvoltage, the bypass element conducts current, thereby creating a current imbalance in the GFI circuitry causing the GFI to open the circuit.

Abstract: A microprocessor controlled automatic transfer switch is provided with an improved voltage sensing scheme which utilizes an open-delta transformer and a control routine for determining voltage level or phase loss. The invention requires only two transformers for sensing three-phase power. An actuator protection feature is also provided to limit the duration of power applied to and to protect the actuator solenoids on the automatic transfer switch. Also provided are improved diagnostic annunciation features which provide specific information regarding switch position and sensing element and/or actuator malfunction.

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: A three wire power supply circuit is provided comprising a circuit for monitoring the integrity of the ground connection of the power supply circuit. A circuit element is provided in the line-to-ground current path which conducts when current flows in the line-to-ground current path and is nonconductive when the ground connection is poor or absent. A microcontroller monitors the output of the circuit element and operates a buzzer or a light emitting diode to indicate when the ground connection is poor or absent.

Abstract: An intelligent circuit interrupt system is electrically connected between an AC source and a load for interrupting a flow of AC from the source to the load upon detection of an interrupt condition. A circuit interrupter electrically connected to phase and neutral terminals of the AC source defines the interrupt condition. A relay switch with a relay coil and phase and neutral contacts is included such that line and load ends of the phase contact are electrically connected, respectively, between the interrupt means load side phase port and a phase terminal of the load. Line and load ends of the neutral contact are electrically connected, respectively, between the interrupt neutral port and a neutral terminal of the load. The relay coil is electrically coupled between load sides of said phase and neutral contacts for controlling the contacts in response to the interrupt signal.

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: Wiring harnessess are current feedback paths from the loads to a battery, thereby forming a closed-circuit. For each load, there are provided a current detector and a current control; each current detector compares the current input to a junction box to the output current from the corresponding load via a corresponding wiring harness, and outputs a normal state signal when the two currents are equal. When the input and output currents are at variance with each other, it outputs an abnormal state signal. Each current controller causes, upon receipt of the normal state signal, the input current to flow into the corresponding load along normal current path; upon receipt of the abnormal state signal, the input current is directed to flow to a current cutoff which includes a thermal device which is disposed in parallel with the current path and whose resistance value changes with temperature, thereby cutting off the flow of current to the load.

Abstract: A portable ground fault interrupter is provided which includes a strong environmentally durable housing and plug inputs for plugging into an electrical outlet. The housing also contains receptacles to accept an electrical plug. A plurality of first electrical contacts are within the housing and stationary relative to the housing. A second plurality of electrical contacts corresponding to said first contacts are suspended within the housing by electrical conducting strips which biasingly move the second contacts away from the first contacts. A latching assembly selectively and operably engages said second contacts to overcome the force of the suspending strips to move the second contacts into electrical engagement with the first contacts. Occurrence of a ground fault removes the latching assembly from engagement with the second contacts breaking electrical contact between the first contacts and second contacts.

Abstract: An in-line cord ground fault circuit interrupter which contains within a common housing the sensing unit and the tripping relay usually found separately packaged at a remote location. The fixed contacts are mounted on fixed contact arms mounted adjacent one surface of a printed circuit board with the movable contacts mounted on movable contact arms mounted adjacent the second surface. The tripping relay operates an armature between an open and a closed condition and by cams on the arms of the armature opens and closes the movable contacts with the fixed contacts. The two portion housing allows the components of the interrupter to be mounted on one portion of the housing which also supports the line and load conductors making assembly of the rear housing portion to the front housing portion easy.

Abstract: A transformerless conditioner of a power distribution system consists of an electronically enhanced filter (EEF) for suppression of transient impulses on the power line and neutral line, and a transformerless ground conditioner for suppression of transient impulses on the ground line. The filter includes a normal mode filter having an inductor located on the power line and an inductor located on the neutral line between source and load of the power distribution system, and a pair of capacitors arranged in series and connected between the power and neutral lines, whereby a midpoint tap is formed between the pair of capacitors. The EEF also includes a unique common mode filter which is formed by the series connection of either inductor of the power line or the neutral line, or both, to its corresponding capacitor and then to the midpoint, from which an electronic impulse detector is connected to ground.

Abstract: A ground fault circuit interrupter (GFCI) line cord plug utilizes an electronically latched relay, rather than a circuit breaker or other type of mechanical latching device, to interrupt the AC load power when a ground fault condition occurs. In order to reduce the size of the relay and minimize the cost and complexity of the GFCI plug, the fixed and movable relay contact structures are mounted directly to the circuit board which carries the remaining components of the GFCI circuit. In a preferred embodiment, the fixed relay contact structures are integral with the plug blades of the GFCI plug. The movable relay contact structures preferably comprise deflectable spring arms which are preloaded when the relay contacts are in the open position in order to control the contact gap, and which are deflected past the point of contact closure when the relay contacts are in the closed position in order to increase the closing force.

Abstract: A ground fault circuit interrupt system with auxiliary surge suppression ability is provided which includes line-side system, phase, neutral and ground terminals electrically connectable to phase, neutral and ground terminals of an AC source and load-side system, phase, neutral and ground terminals electrically connectable, respectively, to phase, neutral and ground terminals of an electrical load. The system includes a ground fault circuit interrupter including line- and load-side phase and neutral ports for electrical connection to the line-side system, phase and neutral terminals for controlling a state of conduction of AC between the source and electrical load in accordance with a detection of an interrupt condition.

Abstract: An electrical extension cord with built-in safety protection includes an electrical cable formed with insulated phase, neutral and ground conductors surrounded by a braided sensing shield. An electrical receptacle is electrically connected to the cable at first ends of each of the phase, neutral and ground conductors, and the shield is electrically connected to the ground conductor. A ground fault circuit interrupter (GFCI) is electrically connected to the cable at second ends of the phase, neutral and ground conductors, within which the ground conductor is electrically coupled to the shield through a predetermined impedance such that leakage current is collected by the shield and detected by the GFCI.

Abstract: A detector for monitoring the integrity of a ground connection to an electrical appliance having live and neutral terminals for feeding current to the appliance from respective live and neutral feeders of an electrical supply having a ground point for connecting to the ground terminal of the appliance. The detector comprises a differential comparator circuit for comparing a voltage at the neutral connection with a voltage at the ground terminal of the appliance and producing a fault signal if a difference therebetween exceeds a predetermined threshold. A normally closed switching device is connected in at least one of the live and neutral connections so as to be opened by a relay operatively coupled to the detector and responsive to the fault signal produced thereby.

Abstract: An intelligent circuit interrupt system is electrically connected between an AC source and a load for interrupting a flow of AC from the source to the load upon detection of an interrupt condition. A circuit interrupter electrically connected to phase and neutral terminals of the AC source defines the interrupt condition. A relay switch with a relay coil and phase and neutral contacts is included such that line and load ends of the phase contact are electrically connected, respectively, between the interrupt means load side phase port and a phase terminal of the load. Line and load ends of the neutral contact are electrically connected, respectively, between the interrupt neutral port and a neutral terminal of the load. The relay coil is electrically coupled between load sides of said phase and neutral contacts for controlling the contacts in response to the interrupt signal.

Abstract: Electronic control apparatus for motor vehicles. The apparatus includes a test circuit which causes a test current to flow through a load being operated by the apparatus and which detects the magnitude of the test current. From the magnitude of the test current, an evaluation circuit determines whether the ground potential of the control apparatus and the ground potential of the load are at different levels. In response to a potential difference between the two ground potentials, the evaluation circuit initiates countermeasures for preventing damage to the electronic control apparatus, such as selectively disconnecting the load with a power switch responsive to the evaluation circuit.

Abstract: A leakage protector comprising a lower and upper cover containing a control circuit which includes a bridge rectifier, a pulse absorber, a light-emitting diode, a comparator, a SCR and a relay wherein the output of the comparator causes the relay to interrupt power to a load.

Abstract: A sum current transformer that acts on a protective switch via an amplifier has a core of a solid metallic material composed of an alloy having more than 40% nickel, so that it can be implemented mechanically solid even given small dimensions. The temperature dependency of the arrangement caused by the ohmic resistance of the winding is compensated by the diminishing eddy currents in the core given increasing temperature, so that the smallest dimensions can be realized for the aggregate current transformer.

Abstract: A method for preventing excessive currents in a welding converter that, by use of power semiconductors, generates a two-phase, pulse-width-modulated a.c current from a rectified mains a.c. current supplied to the primary side of a welding transformer. The method includes the following method steps: detecting the current of at least one phase of the primary circuit by a sensor (20); for each detected current signal, forming the time derivation through differentiation according to the time; comparing the time-derived measured signal with a predetermined maximum value; and if the time-derived measured signal exceeds the predetermined maximum value, emitting a signal that leads to deactivation of the power semiconductors (16).

Abstract: An in-line cord ground fault circuit interrupter which contains within a common housing the sensing unit and the tripping relay usually found separately packaged at a remote location. The fixed contacts are mounted on fixed contact arms mounted adjacent one surface of a printed circuit board with the movable contacts mounted on movable contact arms mounted adjacent the second surface. The tripping relay operates an armature between an open and a closed condition and by cams on the arms of the armature opens and closes the movable contacts with the fixed contacts. The two portion housing allows the components of the interrupter to be mounted on one portion of the housing which also supports the line and load conductors making assembly of the rear housing portion to the front housing portion easy.

Abstract: An earth fault circuit breaker (10) for use in a circuit including an AC power supply and a load (11), which circuit breaker comprises a current-to-voltage converter (12) having two transformers for monitoring the current before and after flowing through the load, a leakage current/voltage detector (13A) for processing the outputs (E1 & E2) of the transformers to produce a resultant voltage, a voltage comparator (16) for comparing the said resultant voltage with a predetermined reference voltage to determine if there is a difference between the two transformer outputs, which is caused by an earth fault appearing at the load, and a switching driver (14) for disconnecting the load from the power supply in response to such a difference between the two transformer outputs exceeding the predetermined reference voltage, wherein each transformer has first and second primary windings (P1 & P2) arranged to be connected to opposite sides of the load and the two transformers are arranged to provide outputs at their resp

Abstract: A new and novel system for protecting people and property against electrical shock. It includes a number of preferred and other embodiments which have this as their goal, but which represent a number of distinctive and novel approaches to solving prior art problems. By way of example only, and without limiting the scope of this invention, these approaches include novel immersion detecting circuits, broken wire test circuits, electromechanical circuit breaking means including coil/plunger arrangements, and relay circuit breaking mechanisms cooperative with associated circuitry, all of which are able to be incorporated as a system wholly within the load (appliance) and its associated cord set (including a "plug").

Abstract: A reverse wiring indicator for a GFCI receptacle alerts the installer in the event that the AC source has been improperly wired to the load or feedthrough terminals of the receptacle rather than to the source or input terminals. The reverse wiring indicator operates by open-circuiting one of the load or feedthrough terminals of the receptacle, and may take the form of a removable barrier which inhibits conduction through one of the power contact sets of the GFCI circuit breaker until the receptacle has been installed and successfully tested. The contact set through which conduction is inhibited is the one other than that to which the TEST switch is connected, and the other contact set is allowed to conduct in the normal manner.