Abstract: The present disclosure relates to resettable circuit interrupting devices and apparatus capable of being tested and reset from remote locations, and in particular to portable circuit interrupting devices and apparatus capable of being tested and reset from remote locations.

Abstract: A basic idea of the invention is to introduce a transmission delay line between the switch and the power output side of a power switching system so that any sparking of the load is hidden from the switch by the time delay of the transmission line. This makes it possible to detect the load spark and actively protect the switch, typically by turning the switch off, before it actually knows that there has been a load fault spark. Alternatively, the delay of the transmission line is long enough so that the switch has already been turned off in normal pulse operation before the load fault current reaches the switch. Either way, the switch will be turned off under normal current flow and will not be subject to destructive over-current or over-voltage conditions.

Abstract: Disclosed is an overload protection delay circuit for use in a switching power supply for enabling the switching power supply to detect overload problems with high accuracy. The overload protection delay circuit is connected between a photo coupler and a pulse-width modulator of the switching power supply, and is consisted of an energy storage device such as a capacitor and a charging controller such as a zener diode. The charging controller is configured to set a limit value for allowing the energy storage device to be charged by an internal current source of the pulse-width modulator when the feedback signal of the switching power supply reaches the limit value. By charging the energy storage device, a time delay is added to the feedback signal so that the pulse-width modulator can accurately activate the internal overload protection mechanism without the interference of load transients.

Abstract: A control circuit includes a detection circuit to detect the short-circuited of a current sense terminal of the power converter. It includes a comparator, a verification circuit and a timer circuit. The comparator receives an input signal for generating a sense signal. The input signal represents the switching current of a power switch. The sense signal is enabled when the input signal is lower than a threshold. The verification circuit generates a protection signal in response to the sense signal or/and -a delay signal. The protection signal is generated when the current sense terminal is short-circuited, in which the power switch and the sense signal are enabled after the time delay of the delay signal. The protection signal turns off the power switch for the protection.

Abstract: For suppressing arc discharges in a plasma process, a method includes monitoring of at least one parameter of the plasma process, determining a temporal feature of a first countermeasure and performing the first countermeasure. The temporal feature is determined as a function of, for example, at least one of an interval in time from at least one previous countermeasure, a development of the at least one parameter since a relevant time of introduction of the countermeasure, or since a variable period of time ahead of the relevant time of introduction of the countermeasure, and a differentiation as to whether a previous countermeasure was triggered based on the behavior of the at least one parameter, or based on the interval in time from at least one previous countermeasure.

Abstract: An electronic self-supplied protection device for automatic circuit-breakers that includes: a supply device that draws energy from the stretch of electrical network protected by said circuit-breaker; a control device with at least two levels of operation, where the first of the at least two levels of operation being associated to the function of protection from instantaneous short-circuit SCinst. In addition, second and possible further levels of operation of the self-supplied protection device are associated with further functions of said protection device; a selective interface device including means for regulating the supply, which, in a first step, immediately following upon closing of the circuit by the circuit-breaker, supply the first level of operation, and, after a controlled period of time, supply also the second and possible further levels of operation of said control device.

Abstract: An apparatus and method for detecting electrical arc faults that has reduced susceptibility to nuisance tripping. The apparatus includes a current sensor, an input sense circuit, an arcing sense circuit, a power supply, a tripping circuit, a processing unit, and an electromechanical interface. The processing unit measures multiple voltage levels provided by the arcing sense circuit during a specified number of consecutive time periods. Next, the processing unit determines the number of consecutive time periods during which the voltage levels exceeded a specified minimum value, take on successively lower or higher values, or fall outside a predetermined normal range of values. Based upon the results of this determination, the processing unit either trips the electromechanical interface to interrupt power to a load, or inhibits tripping of the electromechanical interface, thereby reducing the occurrence of nuisance tripping.

Abstract: A combined arc fault circuit interrupter and leakage current detector interrupter. A current sensor, amplifier, and comparator are employed to detect the presence of leakage current in alternating current power conductors. Upon the detection of an amount of current leakage beyond a threshold level, a relay is opened, disconnecting a source of AC power from a power conductor being monitored, such as an appliance line cord. An arc sensor, envelope detector, amplifier, and microcontroller are employed to detect the presence of an arc fault in the alternating current power conductors. The arc fault detection algorithm implemented by the microcontroller is capable of discriminating between high frequency noise which is not caused by a parallel or series arc fault, with high frequency anomalies which are the result of arcing.

Abstract: A self-excited DC-DC converter comprises a switching element that chops a direct-current input voltage; a smoothing circuit that smoothes the chopped voltage to generate a DC output voltage; a switching control signal generation circuit that generates a switching control signal for the on/off control of the switching element by comparing a feedback voltage of the output voltage and a comparison voltage; an output correction circuit that adjusts the comparison voltage according to an error between the feedback voltage and the reference voltage and, when the output current is in the overcurrent state, reduces the level of the comparison voltage; an overcurrent protection signal generation circuit that, when the output current is in an overcurrent state, generates an overcurrent protection signal for turning off the switching element regardless of the switching control signal; and a delay circuit that delays the overcurrent protection signal. Also, a switching control circuit is provided therein.

Abstract: The invention discloses a digital adjusting method for an optical receiver module, and the method implements real-time monitor of parameters, on-line adjustment and non-linear compensation. The digital optical receiver module includes elements as follow: a voltage output circuit of optical power detection 24, a DC/DC voltage boost circuit 22 and a bias voltage adjusting unit which is consisted of an optical-electronic conversion circuit 21; a digital adjusting unit 25, an analog-digital converter (A/D converter) 26 and a memory 27. The digital adjusting unit 25 makes on-line adjustment and implements temperature compensation and dark current compensation of the optical receiver module. The A/D converter 26 monitors the optical power, the working temperature and the bias voltage of the optical detector in real time. The memory 27 stores parameters of the optical receiver module for comparison with a detected optical power and measured temperature etc. and for on-line interrogation.

Abstract: A power distribution unit that switches off power outlets in the event of an over-current condition by using circuitry that measures how long input current has exceeded a threshold and sending a reset signal to the power outlets when input current has exceeded the threshold for a predetermined time duration.

Abstract: A circuit breaker for a power controller integrated circuit is described where an analog timer and a digital timer are provided in parallel. The digital timer provides a fixed, on-chip maximum delay during an overcurrent condition to ensure the transistor will not be damaged. The analog timer allows the user to select an external capacitor or resistor to provide a delay time that is shorter than the time provided by the digital timer. Accordingly, the power controller retains all the flexibility of an analog timer but prevents the overcurrent exceeding a maximum time limit. An autoretry circuit is also included in the power controller which prevents the duty cycle from exceeding a maximum. The autoretry timer is a digital timer that uses the same oscillator as the digital timer for the circuit breaker so the ratio of the delay times is known fixed.

Abstract: A user adjustment assembly for translating user-adjustable dial settings to tripping levels of an electronic trip unit includes a potentiometer and an adjustment button. The potentiometer is positioned inside a cover of the trip unit and includes a potentiometer button. The adjustment button is coupled to the potentiometer for mechanically adjusting it and includes an insulation disc for increasing resistance to electrostatic discharge, preventing contaminants from entering the printed wire assembly components, and preventing application of downward force to the potentiometer button. The insulation disc has a bottom surface that is dimensioned to be larger than the potentiometer button. The adjustment button includes one or more stops that trigger a fail safe operation mode where the tripping levels are automatically adjusted to higher or predetermined protective levels when the adjustment button is moved to those stop positions. Switch calibration is obviated and the simplified design reduces overall cost.

Abstract: A back-pack power supply module is for a circuit interrupter including an elongated line conductor. The back-pack power supply module includes a housing having an opening therethrough. The opening receives the elongated line conductor, which passes through the opening. A power supply circuit is housed by the housing and is adapted to input a line voltage from the elongated line conductor and output direct current voltages. A capacitive divider circuit includes two capacitors electrically connected in series between a first terminal and an output of the capacitive divider circuit. One of these two capacitors receives the line voltage. The two capacitors are embedded in insulation within one portion of the housing. Another capacitor is electrically connected between a second terminal and the capacitive divider circuit output. The other capacitor is disposed in another portion of the housing opposite the opening.

Abstract: In an overcurrent prevention system for a robot having links connected by joints and an electrical system including electric motors installed at the joint, a power circuit connecting the electric motors to a power source, and drive circuits to supply current to the electric motors, there are provided a switching device installed in the power circuit, a current sensor detecting the current supplied to the electric motors, and the output of the current sensor is compared with a threshold value and the switching device is operated to execute a switching action to cut off the power circuit intermittently during a first predetermined period when the output of the current sensor exceeds the threshold value, thereby protecting the electrical system when overcurrent is detected, without causing functional disablement and/or posture instability of the robot.

Abstract: A voltage regulator has an output circuit for producing from an input voltage a predetermined output voltage to be supplied to a load, an overcurrent protection circuit for preventing overcurrent in the output circuit, a memory for storing control information fed from outside, and an adjustment circuit for adjusting the level at which the overcurrent protection circuit detects overcurrent according to the control information read from the memory. With this configuration, it is possible to accurately detect overcurrent by canceling factors such as individual variations in the characteristics of the circuit components, the influence of stress occurring when the regulator IC is packaged, and fabrication-associated variations in the load.

Abstract: A distance relay apparatus includes a directional relay element which performs computation to detect a fault, which occurs in the forward direction from an installing point of the relay apparatus, based on a voltage and a current which are received from an object to be protected, a zone-1 distance relay element which performs computation to detect a fault within a predetermined zone, a fault detecting relay element which performs computation to detect a fault within a zone that is narrower than that of the zone-1 distance relay element in terms of data time length which is shorter than that used for the computation of the zone-1 distance relay element, and a logic element which outputs a relay signal in accordance with a detecting operation of the zone-1 distance relay element, the fault detecting relay element, and the directional relay element.

Abstract: A drive circuit 21 that controls a switching device 23 ON/OFF and a soft cutoff command circuit that gradually decreases the gate terminal voltage of the switching device 23 when short circuit of the switching device 23 is detected. Additionally, an ON-pulse retention command circuit 11 retains the output of the drive circuit 21 ON when the gate terminal voltage is judged to have exceeded a specified value by a gate voltage judgment comparator 16 that detects the gate terminal voltage of the switching device 23.

Abstract: An electronic fuse comprising an integrated circuit having a control output terminal coupled to a control electrode of a power semiconductor switching device, the power semiconductor switching device being coupled in series with a load between first and second potentials, the integrated circuit further comprising a current sense input for sensing the current through the power semiconductor switching device, the integrated circuit further comprising a driver circuit for driving the power semi-conductor switching device, the driver circuit being coupled to a current limiting circuit responsive to the sensed current in the power semiconductor switching device, the current limiting circuit controlling the driver circuit whereby if the current through the power semiconductor switching device exceeds a predetermined threshold, the current limiting circuit generates a command to pulse the power semiconductor switching device on and off in a period of pulsed operation to maintain the current in the power semiconducto

Abstract: A fault detection system detecting malfunctions or deteriorations, which may result in an inverter fault, is provided. The system has a temperature sensor installed on a semiconductor module to monitor a temperature rise rate. It is judged that an abnormal condition has occurred if the thermal resistance is increased by the deterioration of a soldering layer of the semiconductor module or by drive circuit malfunctions and, as a result, the relation between an operation mode and the temperature rise rate falls outside a predetermined range.

Abstract: A safety device for use in conjunction with a delta-connected three-phase electric appliance. The electric appliance is supplied in a delta connection so that the loads (100, 101, 102) of the appliance with their respective control switches (100a, 101a, 102a) are connected over the phase legs (L1, L2, L3) of a three-phase supply, whereby the safety device comprises a switch unit, a load current sense unit for monitoring the magnitude of current supplied to the loads and a control unit for controlling the switch unit on the basis of the sensed load current. The control unit incorporates a timer and a switch unit control block, the timer having a nominal operating time of the load, at the lapse of which the switch unit shuts off current supply to the load with the provision that the current supply has not already been shut off by the load control switch proper.

Abstract: Disclosed are methods and apparatus for over-current detection in PWM power stages. Disclosed methods and apparatus provide over-current detection with adaptive filtering according to the pulse width of the PWM input signal. Methods and apparatus for their implementation are described for detecting the pulse width of a PWM signal in the PWM circuit. According to the detected pulse width, a digital delay less than the pulse width of the PWM signal is selected from among a plurality of available digital delays. Further, an over-current condition in the PWM power stage is detected. The detected over-current signal is filtered by means of the selected digital delay and an over-current detection result is output.

Abstract: A protection device for monitoring current in a power cable to an electrical device and for controlling a remotely located starter for the electrical device in response to a system controller. The device includes a transformer magnetically linked with the power cable to produce a voltage signal in response to the presence of a changing current within the power cable. An input circuit located in a single housing together with the transformer is electrically connected to the transformer so as to receive the voltage signal. The input circuit produces, in response to the voltage signal, either a first signal or a first circuit condition at the output terminal of the input circuit, representative of the changing current in the power cable. A switch circuit also in the same container with the transformer has a terminal for sensing either a second signal or a second circuit condition of the remotely located system controller.

Abstract: A control arrangement and method is provided for detecting and responding to disturbances in electrical power systems. In a preferred arrangement, an integration is initiated that is based on a comparison of actual voltage of a source and a reference voltage. When the integration exceeds a predetermined value, the source is considered unreliable. Also in a preferred arrangement, a determination is made as to whether or not the disturbance is a downstream fault condition. For example, this is useful for applications where a transfer is made from a first source to a second source when predetermined disturbances are detected. In this manner, the transfer of the load to a second source is avoided which would continue the supply of the downstream fault. Additionally, the arrangement distinguishes between various degrees of disturbances to permit appropriate response based on the severity and type of disturbance. For example, a first immediate response, i.e.

Abstract: A combined current and voltage sensor includes: a combined sensor shell; a current sensor located in the combined sensor shell, the current sensor disposed proximate to said first load strap; and a first voltage sensor located in the combined sensor shell, the first voltage sensor disposed proximate to the first load strap. A circuit breaker includes: a first load strap in electrical communication with an electronic trip unit; a breaker in electrical communication with the electronic trip unit; a current sensor disposed at the first load strap; and a first voltage sensor disposed proximate the current sensor.

Abstract: An arrangement includes two series-connected switching contacts in two contactors. The tripping signal thereof is generated with a variable time offset so that the number of disconnection processes and connection processes, which are carried out first in time, are virtually the same during lengthy use.

Abstract: A system and method to eliminate the influence of Dead Time delay in a PWM driven system. The system is implemented using a switching control circuit to operate a pair of upper and lower switching devices in a standard half-bridge arrangement, wherein both a PWM pulse train input and the direction of current flow (current command direction) are both utilized to operate the switching devices. Depending on the direction of the current command, the PWN pulse train input is directly applied to control one of the switching devices (the first switching device), while the second switching device is kept open at least during the closing time of the first switching device. Thus, a precise average PWM output volgate can be obtained, independent of the Dead Time delay, so that a large Dead Time can be used, to provide a precise voltage output over the full range of the DC power supply, while maintaining high reliability.

Abstract: A protection device for monitoring current in a power cable to an electrical device and for controlling a remotely located starter for the electrical device in response to a system controller. The device includes a transformer magnetically linked with the power cable to produce a voltage signal in response to the presence of a changing current within the power cable. An input circuit located in a single housing together with the transformer is electrically connected to the transformer so as to receive the voltage signal. The input circuit produces, in response to the voltage signal, either a first signal or a first circuit condition at the output terminal of the input circuit, representative of the changing current in the power cable A switch circuit also in the same container with the transformer has a terminal for sensing either a second signal or a second circuit condition of the remotely located system controller.

Abstract: A fault detection system detecting malfunctions or deteriorations, which may result in an inverter fault, is provided. The system has a temperature sensor installed on a semiconductor module to monitor a temperature rise rate. It is judged that an abnormal condition has occurred if the thermal resistance is increased by the deterioration of a soldering layer of the semiconductor module or by drive circuit malfunctions and, as a result, the relation between an operation mode and the temperature rise rate falls outside a predetermined range.

Abstract: The invention relates to an inrush current protection circuit for a power supply. The power supply includes a rectification circuit coupled to a main body of the power supply through an energy-storage capacitor. The main body of the power supply is provided with a reference voltage, and the setup time of the reference voltage is greater than a threshold value. The inrush current protection circuit includes a current limiting resistor coupled between a negative terminal of the rectification circuit and a ground terminal of the energy-storage capacitor for preventing the generation of an inrush current the instant that the power supply is powered on, and a switch coupled in parallel with the current limiting resistor and which is controlled by the reference voltage. When the reference voltage is set up, the switch switches from an open state to a short state, so as to bypass the current limiting resistor.

Abstract: A protection device for monitoring current in a power cable to an electrical device and for controlling a remotely located starter for the electrical device in response to a system controller. The device includes a transformer magnetically linked with the power cable to produce a voltage signal in response to the presence of a changing current within the power cable. An input circuit located in a single housing together with the transformer is electrically connected to the transformer so as to receive the voltage signal. The input circuit produces, in response to the voltage signal, either a first signal or a first circuit condition at the output terminal of the input circuit, representative of the changing current in the power cable. A switch circuit also in the same container with the transformer has a terminal for sensing either a second signal or a second circuit condition of the remotely located system controller.

Abstract: In a digital protection relay with a time sync function, the sampling timing of which is specified based on a reference timing transmitted from a time signal generator to time sync means, with a determination value, the time sync means includes a reception circuit that receives a discrimination code and time data transmitted from the time signal generator, a code discrimination circuit that discriminates the reference timing on condition that the received discrimination code coincides with a desired code, a time calculation circuit that calculates the sampling timing on the basis of the discriminated reference timing and the time data, and a sampling sync circuit that specifies the sampling timing of a digital quantity of electricity on the basis of the calculated sampling timing.

Abstract: A control arrangement and method is provided for detecting and responding to disturbances in electrical power systems. In a preferred arrangement, an integration is initiated that is based on a comparison of actual voltage of a source and a reference voltage. When the integration exceeds a predetermined value, the source is considered unreliable. Also in a preferred arrangement, a determination is made as to whether or not the disturbance is a downstream fault condition. For example, this is useful for applications where a transfer is made from a first source to a second source when predetermined disturbances are detected. In this manner, the transfer of the load to a second source is avoided which would continue the supply of the downstream fault. Additionally, the arrangement distinguishes between various degrees of disturbances to permit appropriate response based on the severity and type of disturbance. For example, a first immediate response, i.e.

Abstract: The present invention provides a short circuit power limiter circuit having a current sensor and a power limiter. The short circuit sensor sends a short circuit flag signal to the power limiter when the short circuit sensor detects a short circuit condition in a target circuit. The power limiter then reduces the power consumption of the target circuit. In a specific example, the power limiter toggles a particular portion of the target circuit on and off to reduce the circuit's average short circuit power consumption. This cycle is repeated as long as a short circuit condition exists.

Abstract: A system and method to eliminate the influence of Dead Time delay in a PWM driven system. The system is implemented using a switching control circuit to operate a pair of upper and lower switching devices in a standard half-bridge arrangement, wherein both a PWM pulse train input and the direction of current flow (current command direction) are both utilized to operate the switching devices. Depending on the direction of the current command, the PWM pulse train input is directly applied to control one of the switching devices (the first switching device), while the second switching device is kept open at least during the closing time of the first switching device. Thus, a precise average PWM output voltage can be obtained, independent of the Dead Time delay, so that a large Dead Time can be used, to provide a precise voltage output over the full range of the DC power supply, while maintaining high reliability.

Abstract: A power module including a self arc-extinguishing type semiconductor such as an IGBT and having a function to protect the semiconductor, i.e., to protect the IGBT against a short-circuit current. Even the IGBT having a collector-emitter saturation voltage VCE (sat) set low can be protected against the short-circuit current, by charging a collector-gate junction capacitor (13) quickly, when a sense current IS to flow through a current sense exceeds a set value, to raise a collector voltage VCE quickly thereby to prevent a collector current IC from increasing, by keeping a gate voltage VGE of the IGBT (12) at a voltage rather higher than a threshold voltage, and by turning OFF the IGBT (12) after a predetermined time.

Abstract: In a switching power unit for performing an overcurrent protecting operation by shortening a switching pulse, an oscillation frequency changing circuit drops an oscillation frequency of an oscillator when an overcurrent is detected by an overcurrent detection circuit, and an RS flip-flop circuit performs the overcurrent protecting operation. When an output voltage is dropped due to a short circuit etc., the oscillation frequency changing circuit further drops the oscillation frequency of the oscillator. In an arrangement in which a frequency under a normal loading condition is made higher by considering the response delay in the overcurrent protecting operation in this manner, an overcurrent detection output is given to the oscillation frequency dropping circuit via the RS flip-flop circuit, so that it is necessary to provide a time constant circuit which prevents hunting and it is possible to miniaturize chip size of an integrated circuit itself.

Abstract: A distributed monitoring and protection system for a distributed power network. The system includes a plurality of high-speed measuring units (MUs), wherein each MU is coupled to a power line to measure values of electrical parameters of the power line. Electrical parameters, such as current, voltage, power and frequency are measured by the MUs. The MUs communicate with a control unit (CU) over a high-speed communications network. The CU includes a processor executing algorithms for evaluating the measured parameters to determine the status of the power network and the MUs. The processor also executes fault detection and isolation by comparing the measured values against predetermined threshold values. When a fault is detected by the CU, protective action, such as tripping of a circuit breaker, may be initiated by the CU directly or by transmitting the tripping command over the high speed data network to a local MU. The local MU may then trip the circuit breaker.

Abstract: A digital electric power inverter comprising: a CPU, a PWM driving circuit, a PWM converting circuit, a rectifying circuit, an AC driving circuit, a DC/AC inverting circuit, a plurality of detecting circuits and an alarm circuit, the power inverter is characterized by that: the entire circuitry thereof is designed to be controlled by the CPU that can accurately control these circuits to endue the power inverter with an intact and multi-selection protecting function, thus render the parts thereof to develop their largest effects.

Abstract: The present invention provides an improved measuring circuit for measuring a current of an inductor with minimum losses and errors. According to one embodiment of the invention, the measuring circuit comprises an op-amp, a RC network connected in a feedback loop of the op-amp, and a scaling resistor connected in series to one of the input terminals of the op-amp. By setting the RC constant of the RC network to be equal to the ratio of the inductor value over its internal resistance value, the inductor current can be derived independent of the frequencies of AC signals.

Abstract: A timer switch for suspending the application of a direct current input voltage to a load upon the detection of a voltage irregularity in the input voltage. The timer switch includes a transistor switch for selectively connecting the input voltage to the load. The timer switch also includes a timing element which detects the presence of a voltage irregularity in the input voltage and controls the state of the transistor switch based upon the detection of a voltage irregularity in the input voltage. The timer switch includes exactly three terminals and is powered by the input voltage. The timing element includes exactly one energy storage element which is represented as a capacitor.

Abstract: The overall characteristic curve for an overload trip should fall monotonically, which isn't always the case for certain choices of set values. According to the invention, the characteristic curve of an overload trip in the overload region (I), for a section of the curve situated before the short-delayed short-circuit region (II), may be set with the delay time (tsdi), which is independent of current and dependent on the short delay time (tsd) and which is at least as big as the short delay time (tsd). The above is particularly advantageous in the case of current measurement by means of Rogowski coils.

Abstract: An electronic tripping device for a circuit breaker contains circuitry for simulating the response curve of a fuse. This circuitry can be controlled by a single setting mechanism representing the nominal currents or rated currents of fuses. This improves the coordination of protection in sophisticated power supply equipment containing both circuit breakers and fuses. Tripping devices equipped with microprocessors or operating in an analog fashion can be configured for the mode of operation. The new protection system achieves particularly safe operation for the user in that the setting mechanism is combined with a rating plug for the “fuse” mode, thus directly setting the tripping device to one current value. In a manner similar to a true fuse, consequently, the setting mechanism is provided with appropriate labeling. The simulated curves may contain a point of inflection below a limit in a lagging manner, to increase the nominal switching capacity and selectivity limit of a circuit breaker.

Abstract: Electrical equipment (14) is safeguarded from damage due to parallel arc faults by a circuit that provides several levels of protection. A semiconductor switch (18) and a current sensor (24) are placed in series with the electrical equipment (14). When the current to the equipment exceeds a first threshold for a predefined period of time, the semiconductor switch (18) is rendered non-conductive until the circuit is specifically reset. When the current to the equipment exceeds a greater second threshold, a pulsed signal alternately places the semiconductor switch (18) in conductive and non-conductive states so that the average current applied to the equipment (14) is within an acceptable level. The pulses are measured to determine whether a parallel arc fault has occurred. When the measured pulses (74) are within a predetermined range, a parallel arc fault is declared and the semiconductor switch (18) is rendered non-conductive.

Abstract: In order to provide a circuit breaker, in particular a residual-current circuit breaker or residual-current device, having a variable time delay, which firstly has a stable no-trip response to short-term fault currents and secondly has a particularly short tripping time both in the event of sinusoidal fault currents and in the event of non-sinusoidal fault currents, a delay circuit is provided which comprises two series-connected comparators with a time-delay module connected between them. In this case, there is a smoothing module upstream of the first comparator.

Abstract: A trip unit connection tester (10) is arranged to test the electrical connections (12) and (14) between a trip unit (16) and actuator (18) mounted within a circuit breaker (20). Tester (10) includes a power source (64) including a positive lead (68), and a negative lead (70). The positive lead (68) is coupled to a two-loop switch (58). The two loop switch (58) toggles between a first loop (98), and a second loop (100). The first loop (98) includes the power source (64), the two-loop switch (58), and the energy storage element (82) wherein the energy storage element (82) stores energy coming from the power source (64). The second loop (100) includes the two-loop switch (58), and the energy storage element (82), connections (12) and (14), and the actuator (18), wherein energy stored within the energy storage element (82) is released to the actuator (18).

Abstract: An exemplary embodiment of the invention is a method for detecting a potentially locked axle on a vehicle propelled by an AC motor. The method includes conducting a speed test by estimating axle speed and comparing estimated axle speed to measured vehicle speed. The existence of a potential locked axle condition is determined based on the comparing of estimated axle speed to measured vehicle speed. Additional tests are disclosed for determining a potential locked axle condition and a sensor fault condition.

Abstract: Arc faults in ac electric power systems including aircraft 400 Hz and other such ac electrical systems are detected by an arc fault detector generating a time attenuated cumulative sum of amounts by which the current in each most recent cyclic interval of current, preferably each half cycle, exceeds the magnitude of the current in the immediately preceding cyclic interval in absolute magnitude after a first cyclic interval in which the current exceeds a selected arming magnitude. Preferably, the magnitude detected by a peak detector is used, but alternatively differences in the average magnitude or the rms magnitude between half cycles can be accumulated. When the cumulative sum reaches a preset value, an arc fault indication is generated. The time cumulative sum is cleared if it decreases to a preset value and the selected arming current must be exceeded again to reinitiate generation of the time attenuated cumulative sum.

Abstract: A contactor includes a switching circuit for switching a load between one or more electrical supplies, a current detector for detecting the current flowing through the load, a trip circuit for tripping the current after an interval of time which depends upon how much the current flowing through the load exceeds a predetermined amount, and a pre-trip circuit for providing an indication during said time interval that the current exceeds said predetermined amount for providing ‘pre-trip’ or ‘near-trip’ information.

Abstract: A telephone line interface circuit is disclosed that functions with use of PTC resistors so that temperature increases within the battery feed resistors is minimized. Utilizing current and voltage feedback loops within the line interface circuit, the PTC resistors are implemented without significantly reducing the performance of the overall circuit that would normally be caused by the PTC resistors' inherent impedance inaccuracies. In normal operation, the feedback loops adjust the current and voltage on the telephone line to the desired level without regard for the impedance values of the PTC resistors. In the case that a high voltage is applied to a telephone line, the significant increase in current flow into the line interface circuit causes the battery feed resistors to heat up, and therefore the PTC resistors, that are physically local to the feed resistors, to heat up and significantly increase in impedance.