Abstract: A switching configuration for electrical control devices, in particular for use in control devices of an electrical system of power-driven vehicles is disclosed. The switching configuration includes a busline with a defined thermal conductivity and a defined heat capacity, which is connected with a first predefined power supply potential. The switching configuration has a plurality of switching devices for switching on and off at least one associated load of a respective switching device, for each of which a first current-conducting connection of the switching device is connected with the busline with a defined thermal conductivity and a heat capacity. Whereby each load of a respective switching device is connected between a second current-conducting connection of the switching devices and a second predefined power supply potential.

Abstract: A high sample rate cosine filter eliminates DC components by summing them such that they sum to zero. A non-orthogonal cosine filter is also provided. When the cosine filter is applied for N=4 samples per cycle, the samples are separated by 90 degrees. However, at higher sampling rates, it is not necessary to wait for 90 degrees to estimate the phasor value. Non-orthogonal components are used to estimate the phasor value. The time delay associated with the cosine filter is reduced in the process.

Abstract: A pulse width modulation driver provides programmable current control for a variety of load current ranges using a modulation feedback block. The block scales a signal representative of a sensed current flowing through the load by a selectable gain multiplier. The scaled signal is compared to a target current value to indicate to a driver control when to generate trigger signals for switching current through the load. In this way, load currents can be amplified to match the operational range of the comparator.

Abstract: The response time of a melting fuse is controlled or influenced by temporarily boosting a threshold level from a first constant value (I.sub.1) to a second dynamic value (I.sub.2) which is then caused to decay in a controlled manner during a fixed time between (t.sub.1) and (t.sub.2) and in accordance with a selectable decay function. If a current (m) flowing through the fuse exceeds the decaying threshold value a fuse blowing current is generated and supplied to the fuse, whereby the fuse blows sooner than it would have, if the excess current had prevailed for a long enough time between (t.sub.1) and (t.sub.X). On the other hand, the fuse does not blow in response to short duration transient excess currents that occur, for example at starting an engine. The engine start impulse which may be used to temporarily raise the threshold value from (I.sub.1) to (I.sub.2) and then cause said controlled decay.

Abstract: A circuit (hereinafter "auto-shutoff regulator") for regulating the power provided to a load automatically opens and closes a switch (hereinafter "protection switch") to keep itself from being damaged by excessive power dissipation. The auto-shutoff regulator includes: (1) a shunt regulator coupled in parallel with the load and a power supply, and (2) another circuit (hereinafter "overpower detector") that monitors the power dissipated by the shunt regulator. The overpower detector has a control line (hereinafter "power shutoff line") that is coupled to the protection switch. When the power dissipated in the shunt regulator exceeds a predetermined threshold, the overpower detector drives a signal active on the power shutoff line, thereby to open the protection switch. Opening of the protection switch shuts off the supply of power to the shunt regulator, thereby to protect the shunt regulator from damage caused by excessive power dissipation.

Abstract: A constant-current regulator regulates and monitors the current fed to one or more downstream loads. It also serves to even out the current fed to the downstream load or loads at the control level or when there is a change in the control level. In order to enhance the security and reliability of operation of such a constant-current regulator when installed in a control and monitoring circuit, control signals having a similar regulating/monitoring content are applied to the constant-current regulator by means of two separate busses (3, 4) in a mutually independent manner. The constant-current regulator is used to carry out a separate plausibility/conformity check of the control signals from the first bus (3) and the control signals from the second bus (4). If a lack of plausibility/conformity is ascertained for the control signals of the first bus (3), the control signals of the second bus (4) are taken as the basis for operation of the constant-current regulator.

Abstract: In a motor drive apparatus, a motor drive circuit includes an H bridge circuit composed of four field effect transistors or FETs, and resistors each having electrical resistance sufficiently higher than that of each of the FETs which would be presented when the FET has an ON-state trouble. These resistors are connected in parallel to the respective FETs. To perform a ON-state trouble detecting test on the individual FETs, an OFF signal is fed to all the FETs. If all the EFTS are free of the ON-state trouble, electric potential, representing a result of higher potential of a battery being divided by the resistors, appears at two input terminals of an electric motor connected to the motor drive circuit. If two of the FETs, having their drains connected to a higher-potential electrode of the battery, have the ON-state trouble, the higher potential of the battery appears at the two terminals of the electric motor.

Abstract: A current source circuit includes a variable impedance circuit coupling the returns of dual-floating power sources, and is configured to limit maximum current output in the event of fault and facilitate detection thereof. The first power source powers the current loop using its source, with the current loop returning through the second power source's return. Control circuitry detects an increase in current beyond the predetermined maximum and appropriately increases the impedance between the first and second power sources returns to limit current provided to the current output to the predetermined maximum. This amount of current is detected by, for example, analog to digital conversion and the fault can thereby be appropriately signaled.

Abstract: A method of performing instantaneous protection in a trip unit is presented. The electronic trip unit includes a microcontroller and associated ROM having trip unit application code, e.g., main functionality firmware, including initializing parameters, and boot code, stored therein and EEPROM having operational parameter code stored therein. An instantaneous protection algorithm (program) stored in the memory of the trip unit has a `WAIT` state and a `RUN` state. In the RUN state samples of the sensed current that classify as points that are accumulated in a point register. Accumulation of a determined number of points qualifies as a peak. These peaks are accumulated in a peak register. If a point is not detected within a determined time period, then the count of peaks accumulated in the peak register is decremented, thereby provided a cooling function. When the count in the peak register exceeds the sensor limit a signal is generated by the microcontroller to initiate the trip.

Abstract: A method of recognizing the contact of an armature in an electromagnetic actuator for activating a setting member that can be brought out of a first set position, counter to the force of a restoring spring, and brought into contact with the pole surface of the electromagnet and held when the electromagnet is supplied with current. The controlled (clocked) current course for the holding phase is detected during the time provided for armature contact, and is converted into a current-proportional voltage, and the converted voltage is differentiated and detected as a recognition signal, both for the normal condition of "armature in contact" and the fault condition of "armature is not in contact.

Abstract: A four-terminal MOSFET, in which no combination of the source, drain, body and gate terminals are permanently connected together, is used as a synchronous rectifier capable of blocking an excessive current in a switching mode DC--DC converter resulting from a short-circuited load. In an N-channel version of the synchronous rectifier, the MOSFET body terminal is normally connected to the inductor in the DC--DC converter and is grounded when an overcurrent condition is detected. In a P-channel version of the synchronous rectifier, the MOSFET body terminal is normally connected to the converter output and is connected to the inductor when an overcurrent condition is detected. In addition, the voltage output by the inductor may be clamped using a zener diode or a snubber capacitor. A MOSFET body bias switching circuit is driven by overcurrent detection circuitry that may also be used to turn off the synchronous rectifier MOSFET gate.

Abstract: A pulse width control IC circuit that greatly reduces price, increases packaging density,and improves reliability for switching power supply units, wherein the IC circuit is on a single chip and includes a main converter control section that controls the ON and OFF actions of a main switch outside the IC, an output MOSFET, and an auxiliary converter control section that controls the ON and OFF actions of the output MOSFET.

Abstract: An apparatus and method for temperature sensing and for detecting cracks or breakage of a windshield. A resistance element is connected to the windshield and a resistance monitoring circuit is connected to the resistance element for monitoring an electrical property of the resistance element. A physical integrity monitoring device can be connected to the resistance monitoring circuit for determining the physical integrity of the windshield based upon the monitored electrical property of the resistance element. Also, a temperature calculator can be used to determine a temperature based upon the monitored electrical property associated with the resistance element and upon a relationship between resistance and temperature that has been stored in a memory device.

Abstract: An overcurrent prevention circuit which removes noise upon transmission of a signal over a signal line between two devices for which different power supplies are used and prevents overcurrent from flowing through the signal line to prevent an otherwise possible breakdown of the devices or an associated element. Current from a waveform outputting terminal to an external signal line is detected from a voltage drop across a resistance part. Then, in response to a result of the detection, an N-channel D-type MOS transistor which supplies current of an output signal to the waveform outputting terminal is controlled between on and off to interrupt supply of power. Consequently, no overcurrent flows out from the waveform outputting terminal, and a clamp diode for removing noise connected to the waveform outputting terminal does not suffer from a breakdown by overcurrent.

Abstract: Disclosed herein is a hand held electrical appliance including a housing having therein a component operated by electrical current, and a current interrupting device located in the housing, electrically connected between the component and a source of electric current to provide a path for current between the component and the source of electrical current, and including structure located wholly within the current interrupting device and operable to interrupt the current in the path in the event of excessive current in the path within the current interrupting device.

Abstract: An improved plug-in power module for providing a controlled amount of electrical power to one or more remote lighting fixtures or other load is disclosed, the module being configured to sense a ground fault or other current imbalance at the load and, in response, both to trigger the module's circuit breaker to open and to report the occurrence of such a ground fault to a central location. The power module achieves these important functions without adding unduly to the module's complexity or size.

Abstract: In order to increase safety of lift trucks, a weight indication for the driver is provided so that the driver may know how heavy a load he is handling,. This weight indication is obtained by measuring the current to the motor of the hydraulic pump. In order to eliminate the risk that monetary variations may result in faulty measurements preferably a mean value of current is taken for a certain time or the value of the measured current is added during a fixed time interval. Obtained values are then multiplied by a conversion factor so that the weight in, for instance, kilograms is obtained and delivered to a suitable display device. Obtained values also may be used to provide a warning by sound or light should the load exceed the maximum allowed.

Abstract: A method of detecting an abnormal electric current in a vehicle to detect passage of an abnormal electric current through an electric wire for establishing the connection between a load to which electric power is supplied and a power source, the method of detecting an abnormal electric current in a vehicle comprising the steps of: (a) detecting values of electric currents which pass through the electric wire at predetermined sampling intervals; (b) counting the number of times in a unit detection period that a sampled electric current having a value larger than a predetermined value is detected and determining passage of an abnormal electric current through the electric wire when the number of counts is larger than a first number of times; and (c) counting the number of times that a sampled electric current having a value larger than the predetermined value is detected in a unit detection period after the unit detection period in terms of time in a case where the number of counts is smaller than the first num

Abstract: A library apparatus having a motor driving control circuit including a processor, a motor driver circuit, a relay, a motor abnormal condition detection circuit, a current control circuit, an excess current detection circuit, and an abnormal current monitor circuit. The motor abnormal condition detection circuit is connected to the motor driver circuit, and detects an abnormal condition of at least one of the motor and the motor driver circuit. Upon detecting an abnormal condition, the motor abnormal condition detection circuit outputs a motor abnormal condition detection signal which prompts the current control circuit to regulate the current flowing through the motor driver circuit. If the current control circuit is unsuccessful, the excess current detection circuit outputs an excess current detection signal which triggers the relay to close the power source circuit of the motor driver circuit.

Abstract: A device for counting the edges of electric pulses is disclosed and comprises a first capacitor connected in series with a pump circuit, which comprises a first resistance in series with a first diode connected in parallel with a second resistance, and a second capacitor connected in parallel with the first resistance. When a voltage, which is caused by one of the edges of an electric pulse, is applied across the first capacitor and the pump circuit, the first and second capacitors are charged in series with a charge that is essentially determined by the second capacitor. A first input of a comparator is connected to the connection point between the first capacitor and the pump circuit and a second input of the comparator is connected to a comparison potential, in order to indicate that a given approximate number of pulses have been counted when the voltage across the first capacitor exceeds a threshold level determined by the comparison potential.

Abstract: A method employed in a condition monitoring unit (CMU) for monitoring a circuit breaker or interrupter to obtain a substantially undistorted version of a waveform suffering from saturation distortion comprises employing a current transformer (CT) to measure a current waveform. The output of the CT is prone to be a partially distorted waveform. The invention is generic in the sense that it does not require parameters associated with the CT characteristics or with the burden impedance on the secondary side of the CT. A digital representation of the partially distorted waveform is obtained, and then undistorted portions of the partially distorted waveform are identified by comparing the amplitude of the partially distorted waveform within a sliding window to a pair of boundary values and identifying as undistorted those portions having an amplitude between the boundary values. Next, distorted portions of the waveform are separated from the undistorted portions, thereby yielding a data record with holes.

Abstract: A low cost analog arcing detector and a circuit breaker incorporating such a detector provide a variable response time to arcing faults based upon the amplitude of the arcing current. A filter generates pulses having an amplitude proportional to the amplitude of the step increase in current generated by the striking of the arc. The pulses are rectified and the amount by which the single polarity pulses exceed a threshold value, selected to eliminate nuisance trips on current step increases characteristic of some common loads, is integrated by a capacitor connected to a resistor which continually adjusts the capacitor voltage in a sense opposite to that of the pulses. The capacitor and resistor are selected to generate a trip signal as a function of the accumulated, time attenuated magnitude of the step increases in current associated with each striking of the arc current.

Abstract: Problems with inaccuracies in selecting the relay trip current in an overload relay are eliminated in an overload relay employing a custom potentiometer having a resistance that varies at multiple rates to set the trip current value. The dial markings on the trip current adjustment dial are sufficiently spaced to allow for a more precise selection of the relay trip current at the higher ampere settings of the relay.

Abstract: Driver and overload protection circuit for an electrical switch means. Switching control pulses with a minimum edge duration are fed to a two stage comparator circuit having first, lower and second, higher comparator threshold values. When the lower comparator threshold value is exceeded by a switching control pulse, the electrical switch means is rendered conducting. There is provided an overload detection circuit which, upon detection of overload of the electrical switch means, effects switching off of the same. For avoiding that turning on spikes upon each turning on of the electrical switch means, for example when switching capacitive loads, lead to deactivation of the switch means, any overload signal of the overload detector means is blocked as long as the instantaneous voltage value of the particular switching control pulse is not above the upper comparator threshold.

Abstract: A safety apparatus for electric appliances which includes a sensor for sensing that an electric appliance is operating. An alarm coupled with the sensor, whereby an alarm is initiated. A manually operated alarm disabling switch permitting a person supervising the operation of the electric appliance to temporarily disable the alarm for a predetermined time interval.

Abstract: A circuit protects from overcurrent conditions and detects an open electrical load. A microprocessor has at least one microprocessor terminal that is configurable as an output for generating a command signal to an electrical load and as an input for monitoring the condition of the electrical load. A first transistor is operatively connected to the microprocessor terminal and has an output to be connected to the electrical load. The first transistor has ON and OFF states. A second transistor is powered from a power supply and is connected to the first transistor and the microprocessor terminal. The second transistor is operative to generate an output logic signal back to the microprocessor and to latch the first transistor into one of either ON or OFF states under normal load conditions responsive to the receipt of a command signal from the microprocessor, and to maintain the first transistor in an OFF state upon an abnormal overcurrent condition through the first transistor.

Abstract: A regulated power supply for application in a cable signal distribution amplifier comprises a filter, voltage doubler and current sense transformer controlled by a control technique known in the art. In the event of a high impedance short condition causing severe overcurrents, the known control technique is ineffective. To alleviate the problem, a high impedance current fault control circuit includes a sampling circuit, a level adjusting circuit, a differential amplifier for providing a monitor output control voltage and a buffer circuit to the controller. In the event of a high impedance current fault, the control circuit kicks in and interrupts controller operation saving power supply components from damage caused by the overcurrent condition.

Abstract: A circuitry for detecting a fault current or leakage current on the supply line of an electronic circuit includes a current source which is rated for a maximum allowed fault current or leakage current. The current source is fed by an auxiliary voltage source. The potential on the supply line which prevails when the supply voltage is disconnected due to the leakage current is determined and assessed by a potential monitor.

Abstract: A method for applying a modified Discrete Fourier Transform (DFT) in a protective relaying system involves five basic steps: The first step, S1, comprises measuring voltage and current time-domain samples v(k), i(k). The next step, S2, involves the computation of the DFT of the DC component(s) (V.sub.DC (k), I.sub.DC (k)) of the voltage and current samples. The next step, S3, comprises the computation of the regular DFT (V(k), I(k)). Next, in step S4, the modified DFTs are computed as, V.sub.m (k)=V(k)-V.sub.DC (k), and I.sub.m (k)=I(k)-I.sub.DC (k). In step S5 the modified DFT values representing the desired phasors are employed to carry out various protective relaying functions.

Abstract: The battery pack for electric power tools of this invention has a circuit breaker connected in series with the batteries to protect those batteries from abnormal temperature or abnormal current by cutting-off the current. The circuit breaker is provided with a manual reset mechanism wherein even if the temperature sensing element is cooled, automatic reset will not occur. The circuit breaker must be manually reset. After the circuit breaker detects battery abnormality and cuts-off current, the current cut-off state is maintained until the manual reset mechanism is operated.

Abstract: A self-excitation type switch power supply unit with overcurrent protection. For adopting a simple and reliable current negative feedback protective circuit to coordinate with a complementary bridge circuit, a positive feedback circuit without DC biasing capacitive coupling, an oscillation-starting circuit of the AC power supply, etc., so that the self-excitation type switch power supply can become a practical power supply unit with simple circuitry, small size and low cost.

Abstract: An apparatus including only first and second sensors for determining three phase motor currents and providing complete over-current protection to a three phase motor having three input lines. The first and second sensors measure first and second combined currents wherein the first combined current is the current through the first and second lines and the second combined current is at least the current through the second line and at least one of the first or second combined currents include the third current. The first and second combined currents are used to provide the over-current protection and are used to determine all of the first, second and third line currents.

Abstract: Contactor-circuit breaker housing firstly power poles and an electromagnet serving to activate the moving contacts in contactor mode and including a fixed magnetic circuit, a moving magnetic circuit and a coil whose electric supply is controlled by a switch, and secondly at least one current sensor serving to control a releasing electromagnet. The activating electromagnet and the releasing electromagnet are constituted by a single electromagnet whose moving magnetic circuit is a pivoting pallet linked mechanically to the contact-holders of the poles and having a weak moment of inertia. An electric unit is provided for the rapid reduction of the magnetic flux, triggered by an electronic control device associated with the current sensor.

Abstract: First threshold corresponding to a large electric current capable of breaking a MOS-FET even if the electric current flows even in a short period is provided for a difference amplifying circuit and second threshold lower than the first threshold is stored in a memory. If a detected electric current value is higher than the first threshold or if a CPU determines that an electric current higher than the second threshold has flowed continuously for a period longer than a predetermined period, the semiconductor switch is switched off.

Abstract: The circuit breaker comprises a circuit breaker unit onto which there are fixed a communication module, a processing module and a calibration module. The communication module communicates with the processing module only via a connection with galvanic isolation, preferably an optical connection, whereas the calibration module is electrically connected to the processing module. The communication module is, in addition, connected by a mechanical connection to parts of the circuit breaker unit representative of the state of the circuit breaker, and by a bidirectional electrical connection to an external communication bus. An interface connected to the circuit breaker unit can act as support for the calibration module and for an additional module containing information representative of the breaking capacity of the circuit breaker and electrically connected to the processing module.

Abstract: A digitally controlled circuit breaker includes a conventional thermal circuit breaker (10) which is controlled by a solenoid (16) to override the thermal aspect thereof. The solenoid (16) is controlled by a digital processing section (20). The digital processing section (20) has a digital control module (22) with multiple profile tables associated therewith. The profile tables allow the digital control module (22) to compare a sensed current from a sensor (24) with a predetermined current value as a function of time and to generate the control signal for the solenoid (16) if the sensed current exceeds that in the profile. The profiles can optionally be downloaded to the module (22) through a serial communication port (36). The digital control module (22) is also operable to sense the voltage of the circuit breaker to determine zero crossing points and phase angle, which phase angle can be utilized to determine the type of load and, therefore, can alter the profile to be utilized.

Abstract: A clock line over-protection circuit (28) carried on an interface card (16) for interfacing synchronous clock line (20), power line (22), DC common line (24) and data line (26) between a host computer (12) and a plurality of data link modules (14) with a plurality of associated controlled devices (18) including a series resistor (52) interconnected between a clock disable switch (52) and a clock signal generating amplifier (48) and a current sensor circuit (64, FIG. 3) connected across the series resistor (50) to produce a current sensor signal on an output (62). The current sensor signal is integrated by an over-current protection circuit (58, FIG. 4) to produce an over-current detection signal that varies with the difference in the clock line current magnitude during clock signal phases of opposite polarity.

Abstract: A method for configuring a digital overcurrent relay to provide a plurality of selectable time overcurrent characteristic responses corresponding to a plurality of target curves. According to one embodiment, a template curve is selected from the plurality of target curves, and a scaling factor is generated for each remaining target curve, wherein the relay comprises means for generating approximated curves from a given template curve and a given scaling factor. It is determined whether each approximated curve is within a threshold amount of total error with respect to its corresponding target curve. If any approximated curves are above the threshold amount, then a further template is selected from the plurality of target curves, and scaling factors are again generated and adjusted for the further template curve, until no approximated curves are above the threshold amount.

Abstract: The electronic trip device with a thermal memory including a capacitor and a charging resistor arranged in parallel. In normal operation, the capacitor is permanently charged by a supply voltage supplied by the power system to be protected. The trip device includes a processing circuit which performs tripping functions after calculation of a thermal value representative of the thermal state of the power system and detects an imminent drop of the supply voltage. When such a drop is detected, the processing circuit orders discharging of the capacitor until the voltage at the terminals of the capacitor is representative of the calculated numerical value.

Abstract: A machine includes first and second electrically actuated components and a shutdown circuit electrically interconnected therewith. The shutdown circuit has a current sense relay element which is electrically connected to the first electrically actuated machine component. The current sense relay element includes a coil capable of generating a magnetic field in response to direct current flowing therethrough and a reed switch adjacent the coil which is movable between open and closed positions in response to the presence of the magnetic field. The reed switch is normally closed when the direct current flowing to the first electrically actuated machine component is at or above a predetermined level. The reed switch opens when the direct current flowing to the first electrically actuated machine component falls below the predetermined level.

Abstract: Switching devices can have means for contactless switching position detection. According to the invention, magnetic field sensors arranged at suitable locations inside and/or outside a device housing are provided for switching position detection. In particular, position-dependent magnetic fields are measured for ON/OFF position detection, overcurrent triggering, and contact welding; however, the magnetic field of the current flowing is detected to recognize short-circuit triggering. Differential Hall effect sensors and Reed contacts, respectively, can be used for these purposes. In addition, a sound sensor can be provided for detecting the switching noise, whose signal is evaluated together with the overcurrent triggering signal for short-circuit detection.

Abstract: The gating circuit has a power transistor (T1, T2, T3) and a current measuring resistor (R5) connected with the power transistor so that a voltage drop at the measuring resistor is a measure of a current flow in the power transistor. This voltage drop is used to trigger a current regulating transistor (T5) and a temperature measuring transistor (T9). Below a predetermined temperature, the current flow is limited solely by the current regulating transistor (T5). Above this predetermined temperature the collector current is further reduced via the temperature measuring transistor (T9) and a further transistor (T10) so as to protect the power transistor from thermal overload.

Abstract: An overcurrent and short circuit protection device for a power semiconductor component is responsive to output current signals representing the actual output current(s) of the semiconductor component. A short-circuit window comparator receives the output current signals and produces an error signal when the sum of all output current signals is less than a minimum allowable value or more than a maximum allowable value. An overcurrent window comparator receives the same output current signals, determines a positive maximum instantaneous value and a negative maximum instantaneous value, and produces an error signal when either one of these exceeds a maximum allowable value. An error signal from either window comparator interrupts operation of the power semiconductor component and locks out all higher level control signals to the power semiconductor component.

Abstract: An arcing fault detecting module is attached to a circuit breaker employing a thermal-magnetic trip unit to separate the circuit breaker contacts upon occurrence of an arcing fault. The arcing fault module contains a logic circuit and a current transformer for detecting the arcing fault and actuating a trip solenoid to articulate the circuit breaker operating mechanism and separate the circuit breaker contacts.

Abstract: An arc fault detector having a pulse generator generating a pulse each time an arc is struck includes a limiting amplifier which limits the amplitude of the pulses to discriminate against false trips from sizable singular events such as tungsten bulb burnout and turn-on of a cold tungsten lamp controlled by a phased back dimmer. When a time attenuated accumulation of the pulses reaches a predetermined level an arc fault signal which can be used to trip the circuit breaker is generated. The pulse generator of the arc fault detector includes multiple stages of high pass filtering which produces overshoot and therefore additional pulses each time an arc is struck. As only the additional pulses associated with large amplitude arcs exceed a threshold value for inclusion in the time attenuated accumulation, compensation for the reduction in sensitivity to large amplitude arcs imposed by the limiting amplitude is provided.

Abstract: A method and apparatus is disclosed for complete three-phase sensing using two current transformers. Two phases of a three-phase system are used as the primary windings in each current transformer such that each current transformer produces a phasor representation of a sum of the two phases. A three phase sensor is provided to add the phasor representations produced by each of the current transformers and to produce a third phasor representation from the summation. The three phasor representations can then be applied to any conventional overload relay control to monitor each phase and produces a trip signal to open the three-phase system when a phasor representation exceeds some predetermined value, or the magnitudes of the phasors differ by more than a predefined value.

Abstract: A control circuit and method are provided for a circuit interrupter that predicts the occurrence of fault-current zero crossings. This prediction is utilized to control the operation of a circuit interrupter at a desirable point in the periodic wave form of the fault current. For example, the control circuit is useful to control a synchronous interrupter by accurately generating a trip signal to the synchronous interrupter for operation in the vicinity of the zero crossing of the current wave form. In a preferred arrangement, the control circuit utilizes the quotient of a sensed current signal and the time rate of change of the sensed current signal. In one specific arrangement for circuit environments that might include conditions that could lead to false results, the time rate of change of the quotient is utilized to provide a control signal.

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 stabilized power source circuit is provided with an over current protecting circuit which obtains either a current value or a voltage value corresponding to an output current value of an output transistor as a detected value, compares the detected value with a predetermined constant value and lowers the output current when the detected value exceeds the predetermined constant value. A comparing value generating circuit receives an external signal, generates one of either a predetermined plurality of voltage values or a predetermined plurality of current values in response to the level of the received external signal and transmits the same to the over current protecting circuit as the predetermined constant value.

Abstract: A time-compensated overcurrent detection circuit shuts off a D.C. motor during large overcurrent conditions caused by actual constraints on the motor. The circuit prevents premature motor shut off by establishing a minimum activation time for shutting off the D.C. motor. An overcurrent time compensator establishes a minimum time period for activating a motor reset signal after sensing an overcurrent condition. The circuitry uses a relatively small capacitor that provides quick response to overcurrent conditions.