Abstract: A drive circuit includes: a current capability switch configured to switch a current capability of driving an output transistor of a switching power supply according to whether a switch current flowing through the output transistor is in a continuous mode or in a discontinuous mode.

Abstract: A watt-hour meter may include one or more electrical junction points that interface a Distributed Energy Resource to an energy-consuming structure and to the electrical distribution grid, while maintaining compliance with interconnection requirements for safety, power quality and automatic disconnect capabilities.

Abstract: A protection monitoring system is provided that includes a protection fault handler. The protection fault handler includes a protection fault indicator. The protection fault handler is configured to activate the protection fault indicator upon indication of a protection fault signal. Moreover, the protection fault signal is indicative of a critical fault which has occurred in a protection system monitored by the protection monitoring system. The protection monitoring system also includes a user inhibit handler. The user inhibit handler includes a user inhibit indicator. Moreover, the user inhibit handler is configured to activate the user inhibit indicator upon indication of a user inhibit signal. Furthermore, the user inhibit signal is indicative of a user-enabled alarm inhibit or a user-enabled bypass.

Abstract: A server rack includes a mapping module having management ports that are each uniquely associated with and collocated with a rack unit of the server rack, a server installed in a rack unit of the server rack having a host port and a management controller coupled to a management port, and a rack switch including a first switch port coupled to the host port. The management module provides an indication to the mapping module that the host port is an active port, and the mapping module directs the rack switch to query the switch port to determine if the switch port is coupled to the active port in response to receiving the indication, receives a second indication that the switch port is coupled to the active port, and provides a network map for the server rack that indicates that the host port is coupled to the switch port.

Abstract: An arc resistant system includes an enclosure that houses electrical equipment and includes an intake isolation assembly configured to deform in response to an arc fault pressure wave to substantially block an intake ventilation opening of the enclosure. The enclosure also includes a first pressure relief assembly configured to open in response to the arc fault pressure wave to allow arc products to exit the enclosure and to enter a ventilation box. The ventilation box is coupled to the enclosure and includes an exhaust isolation assembly configured to deform in response to the arc fault pressure wave to substantially block an exhaust ventilation opening of the ventilation box. The ventilation box also includes a second pressure relief assembly configured to open in response to the arc fault pressure wave to allow the arc products to exit the ventilation box.

Abstract: A high-power conversion system includes a switching circuit and at least one reactor, the at least one reactor being electrically connected to the switching circuit, and the core of the at least one reactor being electrically connected to a potential point of the high-power conversion system.

Abstract: An electronic control unit includes a microcomputer and a power circuit that supplies an electric power to the microcomputer. The microcomputer and the power circuit respectively operate in a normal operation mode and in a low power operation mode that consumes less power than the normal operation mode. The electronic control unit further includes a mode switcher for switching the operation modes of the microcomputer and the power circuit according to an input signal from an external device. When a mode switch signal for switching the operation mode of both devices to the normal operation mode, the mode switcher first switches the power circuit to the normal operation mode and subsequently switches the microcomputer to the normal operation mode, which prevents a reset operation of the microcomputer without using a large capacity capacitor.

Abstract: An IC driver includes a resistor detector to detect whether at least a threshold resistance is present between a pin of the IC driver and the gate of an IGBT. The resistor detector can include a comparator that compares a voltage at the collector of the IGBT to a threshold reference voltage (e.g., ground). In response to drive signals of the IC driver being switched off, a parasitic inductance causes a voltage drop at the emitter of the IGBT, and a commensurate voltage drop at the IGBT collector. If the resistance between the IC driver pin and the IGBT gate is lower than a specified level, the voltage drop at the IGBT collector will be such that the collector voltage falls below the threshold reference voltage. In response, the comparator asserts a signal indicating a fault.

Abstract: Methods and apparatus for providing a system, such as a power conditioner unit, including terminals to receive three-phase signals, respective filter inductors, and respective filter capacitors that are switched into the EMI filter when the loading is above a given threshold.

Abstract: The present invention relates to an electrical device for charging accumulator means (5), said electrical device comprising: a motor (6) connected to an external mains (11); an inverter (2) connected to the phases of said motor (6); and switching means (4) integrated into the inverter (2), said switching means (4) being configured to permit said motor (6) to be supplied and to permit the accumulator means (5) to be charged by the inverter (2). According to the invention, said electrical device further includes, for each phase of said motor (6), an RLC low-pass filter (18) connected, on the one hand, to the mid-point (16) of the phase of said motor (6) and, on the other hand, to ground.

Abstract: The present invention discloses methods for protecting a peripheral device in a computing system from electrical surge currents, the method including the steps of: providing a controller operationally connected to a host system; and reversibly conductively connecting, via the controller, wires of the device to the host system. Preferably, the device is connected to the host system via a connector. Preferably, the device is hard-wired to the host system. Preferably, at least some wires of the device are isolated from the host system via a mechanical contactor. Preferably, at least some wires of the device are isolated from the host system via an optical isolator. Preferably, the method further includes the step of: charging a switching battery when the device is disconnected from the host system. Most preferably, the method further includes the step of: powering the device using the battery when the device is connected to the host system.

Abstract: A control portion instructs supply of an offset voltage while a disk remains stopped at the time of start. While the disk remains stopped at the time of start, a differential operational amplifier detects a voltage difference between a first voltage supply line and a second voltage supply line. When the absolute value of the voltage difference output by the differential operational amplifier is equal to or lower than a prescribed threshold value, a failure determination portion determines that a spindle motor has shorted out.

Abstract: A terminator reduces reflections on power lines connecting an inverter to an AC motor by providing a differential-mode reflection damping element and at least one common-mode reflection damping element, the latter including a series capacitance to substantially reduce power dissipation in the resistance of the damping elements.

Abstract: A wiring and power distribution device for a cabinet housing electronic equipment. The distribution device includes a plurality of compartments. Each compartment adapted to contain an electronic component, such as an uninterruptible power supply, a power-conditioning device, or a power distribution center containing circuit breakers. The distribution device also includes a cooling compartment, including a fan or passive convective chimney arranged to cool the interior of the cabinet with ambient air. The distribution device provides a single input point for power and signal wiring, and at least one output point for connection to the electronic devices contained within the cabinet.

Abstract: An electrostatic discharge (ESD) protection clamp (61) for I/O terminals (22, 23) of integrated circuits (ICs) (24) comprises an NPN bipolar transistor (25) coupled to an integrated Zener diode (30). Variations in the break-down current-voltage characteristics (311, 312, 313, 314) of multiple prior art ESD clamps (31) in different parts of the same IC chip is avoided by forming the anode (301) of the Zener (30) in the shape of a base-coupled P+ annular ring (75) surrounded by a spaced-apart N+ annular collector ring (70) for the cathode (302) of the Zener (30).

Abstract: A system for coupling an avionics component to a bus includes a junction box electrically coupled to the avionics component and to the bus. A circuit card disposed in the junction box includes a plurality of sockets. The some of the sockets are electrically connected to the bus. Others of the sockets are electrically connected to the avionics component. A modular network bus coupler is mountable to the circuit card. The bus coupler includes a housing with electrical isolation circuitry disposed therein. A plurality of pins are disposed exterior of the housing and engageable with at least some of the sockets of the circuit card. At least some of the pins are electrically coupled to the electrical isolation circuitry.

Abstract: A disc apparatus which can accurately judge whether or not a spindle motor is at fault due to a short circuit is provided. A disc apparatus (1) includes a spindle motor (3) which rotates a disc (2), a differential operational amplifier (5) which detects a difference between voltages of a positive terminal and a negative terminal of the spindle motor (3) as a detecting voltage level, a failure judgment unit (10) which judges whether or not the spindle motor (3) is at fault based on the detecting voltage level, and a disc determination means (12) which determines a type of the disc (2). The failure judgment unit (10) judges that the spindle motor (3) is at fault when the detecting voltage level becomes lower than a predetermined threshold level five times continuously during a start-up that the spindle motor (3) starts driving when the disc (2) is in stopped state while the disc determination means (12) determines the type of the disc (2).

Abstract: A circuit board includes a power switch operable so as to generate a trigger signal upon actuation, a card slot adapted for connecting with a video card, and a controller coupled electrically to the power switch and the card slot. The controller detects connection of the video card to the card slot and further detects operating voltage of the video card. The controller inhibits the power switch from generating the trigger signal upon detection that the operating voltage of the video card that is connected to the card slot is higher than a predetermined voltage.

Abstract: An apparatus and method for providing a transient connection port are provided. Further, an apparatus and method for switching between a permanent connection port and a transient connection port are provided. The apparatus and method include a permanent connection port and a transient connection port located at the rear of a rack mounted server system and the front of the rack mounted server system, respectively. The permanent connection port operates when there is an absence of a connected device at the transient connection port. When a device is connected to the transient connection port, a signal is sent to a logic switch which causes the active input to be switched from the permanent connection port to the transient connection port. When the device is no longer connected to the transient connection port, the absence of the signal from the transient connection port causes the logic switch to switch the active input back to the permanent connection port.

Abstract: A method of protection in an electronic trip unit is described herein. The method includes selecting a limit value. The method further includes sensing an electrical signal to provide corresponding first and second sensed signals, each indicative of an electrical characteristic of the electrical signal. The first and second sensed signals are compared to determine a rate of rise of the electrical characteristic, and the rate of rise is compared to the limit value to detect a spike in the electrical characteristic. The generation of a trip signal is withheld when the rate of rise is greater than the limit value.

Abstract: A circuit for protecting a microprocessor in a controller for controlling a coin validator from noise includes a noise detector and the circuit is configured to temporarily halt the microprocessor when noise is detected.

Abstract: Semiconductor device according to the present invention includes package frame, bonding wire, pad, first internal power supply line, second internal power supply line, internal circuit, stabilize circuit, GND package frame, GND bonding wire, GND pad, and internal GND line. Bonding wire, pad, and first and second internal power supply lines and function as a filter. As a result, noise generated by operation of internal circuit is absorbed in propagating to stabilize circuit through first internal power supply line, pad, and second internal power supply line. Therefore, effects of noise given to stabilize circuit is small.

Abstract: An electrostatic breakdown prevention apparatus is disclosed which allows an electronic apparatus connected to a connector to bidirectionally transfer data at a high speed on the same signal line and prevents an electrostatic breakdown of the electronic apparatus without relying upon the structure of the connector. A signal line on an electronic apparatus body side is provided with an electrostatic breakdown preventing smoothing circuit for smoothing a signal inputted to the signal line. A connector for connection of the signal line is provided with a switching mechanism for stopping the smoothing function of the electrostatic breakdown preventing smoothing circuit when the connector is connected, but restoring the smoothing function of the electrostatic breakdown preventing smoothing circuit when the connector is disconnected.

Abstract: According to an aspect of the present invention there is provided an LSI device having an output terminal outputting a data, comprising a data output circuit connected to the output terminal and capable of adjusting an output impedance thereof; and an adjustment circuit which detects a transient voltage at the output terminal when an output logic of the data output circuit is switched in a condition that a transmission line not terminated by a terminating resistor is connected to the output terminal, compares the transient voltage with a reference voltage, and adjusts the output impedance of the data output circuit so as to match a characteristic impedance of the transmission line.

Abstract: There is provided a cable which retards lightning. The cable includes at least one internal conductor which may be a power conductor or a signal conductor. A choke conductor is wound about the internal conductor in the shape of a spiral. If lightning strikes near the cable or a device which is attached to the cable, such as an antenna, the choke conductor presents a high impedance to the current caused by lightning and will prevent the lightning current from flowing down the choke conductor, thus entering the internal conductor, thereby preventing damage to the internal conductor and any associated electronic equipment. Preferably, a shield is also wound about the internal conductor adjacent to the choke conductor in a direction opposite to the choke conductor, whereby the angle formed by the crossing of the choke conductor and the shield is approximately 90° to block the magnetic field component of the lightning discharge.

Abstract: A phase control switching system for controlling opening and closing timings of a power switching device to suppress the occurrence of an exciting rush current or a make-and-break surge voltage which is severe to system equipment such as a transformer, a reactor and a capacitor bank, or for controlling an arcing time of a circuit breaker to put the circuit breaker into operation for the arcing time leading to no-re-ignition or for the optimal breaking time. In the phase control switching system, a current measuring section or a current gradient measuring section is provided to measure a current value or a current gradient value of a current to be broken or introduced, and a reference phase detecting section estimates a current zero point of a current waveform on the basis of the measurements. Subsequently, a control section, upon receipt of an opening/closing command, an opening phase control operation using an arbitrary time point after the current waveform estimation as a reference.

Abstract: An off-chip driver (OCD) circuit including a clamp circuit to limit overdrive is provided. The circuit comprises an input signal which is inverted to provide an output signal. The driver circuit is comprised of a source-follower transistor to pull-down the output signal. The clamp circuit actively feeds back the source-follower potential to slow down the OCD and minimize ground bounce and noise that causes circuits to fail and signal integrity to be corrupted. The simple drive and clamp circuit is comprised of three transistors, one resistor, and one capacitor. The OCD slew rate is controlled by a current source and provides an output that changes between a positive voltage and ground. The circuit limits dv/dt without using a large resistor as a source follower, hence minimizing the adverse effect on performance.

Abstract: power source conversion device capable of eliminating low-frequency radiation consisting of electronic circuit is designed to convent the marketable 2-hole type socket power source into 3-hole type socket so as to restore the characteristics of original 3-hole type power source through human body or electronic appliance housing or referable zero potential point, wherein the third hole is substitutive ground point to develop the effect of electromagnetic screening device built in the electric appliances in general for achieving good grounding and eliminating electromagnetic radiation and effect of electric leakage on human body because of poor insulation or induction, and meantime, through the functions of automatically detecting LIFE and NULL and such lines as actuating, locking, safe and warning, an intelligent power source conversion device with overall functions is well combined.

Abstract: Electrical modules which incorporate multiple state input circuitry limit the in-rush current thereto when electrical energy is initially applied. The input circuitry exhibits a high impedance and subsequently a very low impedance state. When electrical energy is first applied, the high impedance state limits the in-rush current to an acceptable predetermined maximum value. Subsequently, in response to either elapsed time or an electrical parameter such as current flow, the circuit switches to a low impedance state which results in its having no material effect on the operation of the module. The module can incorporate a visual alarm indicating output device, an audible alarm indicating output device or both. The output indicating devices can be synchronized by applied control signals. The output devices can be controlled independently by means of either pulse width modulated control signals or by means of patterns of control pulses.

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: There is provided a cable which retards lightning. The cable includes at least one internal conductor which may be a power conductor or a signal conductor. A choke conductor is wound about the internal conductor in the shape of a spiral. If lightning strikes near the cable or a device which is attached to the cable, such as an antenna, the choke conductor presents a high impedance to the current caused by lightning and will prevent the lightning current from flowing down the choke conductor, thus entering the internal conductor, thereby preventing damage to the internal conductor and any associated electronic equipment. Preferably, a shield is also spiraled wound about the internal conductor adjacent to the choke conductor in a direction opposite to the choke conductor, whereby the angle formed by the crossing of the choke conductor and the shield is approximately 90.degree. to block the magnetic field component of the lightning discharge.

Abstract: An express down vehicle window lift motor drive system in which an overcurrent detection circuit (10) interprets the flow of electrical power to the lift motor when the motor current exceeds a threshold which is set dynamically as a function of motor in-rush or peak current. Motor current is measured as a small voltage drop across a current shunt. When the current level rises above the dynamically set threshold energization of the motor is halted.

Abstract: Static isolator for the DC supply circuit of a load (MO) in the event of a surge, consisting of a dipole intended to be inserted into the power circuit of the load and comprising means for detecting a surge (R1, R2, T3, CI), means for filtering and storing the supply voltage (C, R1), means for cutting off the supply to the load (T3, R2, R8, R9, T4, T1, R7, R4), means for detecting the disappearance of the supply voltage (C, R1, R3, R6, T6) and means for erasing the storage means (R2, R6, T3, T6).

Abstract: Semiconductor device according to the present invention includes package frame, bonding wire, pad, first internal power supply line, second internal power supply line, internal circuit, stabilize circuit, GND package frame, GND bonding wire, GND pad, and internal GND line. Bonding wire, pad, and first and second internal power supply lines function as a filter. As a result, noise generated by operation of the internal circuit is absorbed in propagating to the stabilize circuit through first internal power supply line, pad, and the second internal power supply line. Therefore, effects of noise given to the stabilize circuit are small.

Abstract: A power-line trip circuit models the transient characteristic of a change in load (e.g. appearance of a fault current, or switch-on to a normal load) and compares the current actually flowing in the power lines with this modelled or simulated transient. Line currents that do have a transient component but do not exceed normal limits are not then sufficient to trip a circuit breaker associated with the power lines, whereas transient-bearing currents that do exceed such limits, i.e. fault currents, are recognized as such and the circuit breaker is tripped. This circuit allows fast, reliable tripping even in the presence of a substantial transient overshoot.

Abstract: A transformer. According to one embodiment, the planar transformer has a first winding, a first conducting surface adjacent to the first winding, a second winding and a second conducting surface adjacent to the second winding. The first conducting surface is coupled to a first ground and the second conducting surface is coupled to a second ground.

Abstract: A circuit card is interfaced to a powered electrical bus by applying power to the circuit card before it interfaces to the electrical bus or by removing power from the circuit card after it has been removed from the bus. This is accomplished using a power cord that connects the equipment's power supply to a mating connector on the card to be inserted or removed. Attaching the power cord to the mating connector of the card disables the output drivers that provide output signals to the equipment's communication bus and places the card in a reset state. This prevents introducing error signals onto the communication bus. Additionally, the contacts on the edge connector are sequenced to prevent applying power to the circuit card before a ground is available. Additionally, the power cord and circuit card are keyed to prevent improper insertion and the power card includes an inductor to provide surge protection.

Abstract: An overload protecting device which includes a comparator 11 to which an output voltage V10 in proportion to the current flowing through a motor 5 and a start detecting reference voltage E11 are inputted, and a comparator 13 to which the output voltage V10 and an overload detecting reference voltage E13 are inputted, a starting timer 14 for clocking a first period of time T1 lapsing since the output of a signal from the comparator 11, an overload timer 14 for clocking a second period of time T2, which is shorter than the first period of time T1, lapsing since the output of a signal from the comparator 13, a transient finish detecting circuit 300 for outputting a signal V33 representing a finish of transient of the motor 5 finish based on signal outputted from the comparators 11 and 13, and an overload trip relay 18 for cutting off a motor current to the motor 5 through the logical operation of the signal V33 representing motor transient finish or an output signal V12 from the starting timer 12, with an output

Abstract: A circuit interrupter including an improved arc detection system which trips the interrupter in response to currents having frequencies and/or characteristics associated with arcing within the associated alternating current electrical system. The arc monitoring circuit determines if the signal produced by a current transducer is the result of arcing. The arc detection system includes two swept filters and associated amplifiers which produce a signal which has an amplitude representative of the frequencies present in the alternating current of the electric system. The portion of the filtered signal which has amplitudes above a predetermined level is integrated to produce a trip signal for the circuit interrupter when the value of the integration exceeds a predetermined limit.

Abstract: An automatic fault monitoring system prevents the detection of fault conditions during operating modes or conditions that can produce false fault conditions. A motor control system that utilizes an H-bridge circuit having active devices, preferably field effect transistors, in each arm of the bridge. The motor is connected in the leg of the bridge. Currents and voltages are sensed in each arm as different operating conditions represented by input control signals, which may be computer generated, drive the bridge and place the transistors in different states (on or off). Such operating conditions include rotation of the motor in opposite directions and reversal of direction. Fault detection logic is responsive to currents and voltages in the arms and leg of the bridge and provides outputs indicative of over-current fault conditions in the arm and open circuit fault conditions in the leg.

Abstract: Individual devices of a redundant array of independent devices (RAID) are coupled to an electrical power supply. For devices having widely varying load impedances, such as disks, incident with the coupling of electrical power thereto, the replacement or addition of a device in the system, while the system is in operation, causes unacceptable power transients in the power supply. To minimize such power transients, a transient suppression circuit is employed to isolate the load impedance of the device from the power supply. Isolation is achieved in the transient suppression circuit by employing an active circuit element, such as a MOSFET power transistor, as the power coupler. A capacitor controlled voltage divider circuit, incident with the coupling of electrical power thereto, couples a time varying gate voltage, which changes as a function of the rate of charge of the capacitor, to the MOSFET power transistor.

Abstract: An active clamp circuit for controlling over-voltage, surge conditions in electrical circuits. The active clamp includes a varistor which is switched into a circuit by a high power switch upon the detection of a surge condition. The use of a MOS Controlled Thyristor ("MCT") as a means for the switching the varistor permits the circuit to withstand a high di/dt and surge current while maintaining both on and off gated control of the switch.

Abstract: A fiber to curb and telecommunications T1 carrier overvoltage protection apparatus includes a pair of semiconductor junction breakdown crowbar devices connected in series between TIP and RING telephone lines, and a reverse standoff voltage breakdown zener-type device connected between ground potential and a junction connection of the series connected semiconductor junction breakdown crowbar devices.

Abstract: An overvoltage protection circuit (11) for decoupling circuitry (12) from a voltage applied to an input (38). The overvoltage protection circuit (11) is integrated on an integrated circuit along with the circuitry (12). The overvoltage protection circuit (11) comprises a sense circuit (13), a timing circuit (14), a decoupling circuit (16), and a circuit (17). The sense circuit (13) detects when the voltage applied to the input (38) exceeds a threshold voltage. The timing circuit (14) is responsive to the sense circuit (13) and determines when the voltage exceeds the threshold voltage for a predetermined time. The decoupling circuit (16) is responsive to the timing circuit (14) and decouples the circuitry from the voltage applied to the input (38). The circuit (17) generates a logic signal indicating the circuitry has been decoupled.

Abstract: The present invention discloses a gas venting system for use in metallic enclosures housing electrical circuit breakers of the type having gas vents in the circuit breaker case for venting gases produced during the interruption of a fault current. The enclosure includes one or more covers which provide access to the interior of the enclosure and one or more vents through which the circuit breaker gases can exit the enclosure. The gas venting system includes a gas chute made from an electrically nonconductive and substantially flame retardant material. The gas chute is generally tubular and hollow in shape and has a breaker end aperture and at lease one vent end aperture. The apertures communicate with one another through the hollow gas chute.

Abstract: The live insertion circuit of the present invention comprises a movable magnetic body for changing an inductance of a variable inductor, and the movable magnetic body is moved toward a supporting member by a rod at the time of inserting the package into the unit. At this time, an inductance of the variable inductor is changed according to the connection condition of terminals for connecting the package and the unit, thus suppressing a surge current.

Abstract: The condition of signal lamps (R1, R2) in a traffic light system is monitored by compiling a table of power consumption levels at different levels of applied voltage. The table is then used to adjust measured levels of power consumption at intervals during the service life of the traffic light system. A fault condition is signalled if the adjusted values differ by more than a predetermined amount.

Abstract: A circuit for controlling the power supply of an electrical load, having a device for detecting a short-circuit of the load. The detection device has a comparator which supplies a signal representative of a short-circuit state of the load when the voltage at the terminals of that load, after filtering, is below a reference voltage Vref. The device has a circuit for rapidly pre-charging a capacitor of the filter, when the load is switched on. The initial time interval during which the output signal of the comparator is not representative of the presence or absence of a short-circuit is thus reduced. The circuit is applicable to the control of actuators in motor vehicle electronics.

Abstract: An input protection circuit for an electronic circuit includes a switching circuit operable between an ON state and an OFF state for generating an input for the electronic circuit, a first circuit responsive to an excess level of input for forming a clamping circuit across a first resistor for shunting an excess level input, a second circuit monitoring an input from the switching means for detecting a state of the switching circuit for producing an ON/OFF signal depending upon the detected state of the switching circuit, the second circuit including a second resistor which forms a series circuit with the first resistor and the switching circuits while the switching circuits is in an ON state. The switching circuits is operated to an ON position for establishing the series circuit for setting the level of the input at a minimum level and to an OFF position for opening the series circuit for setting the level of the input at a maximum level.

Abstract: An autoconverter has an electronic switch activated by turn-on pulses and a circuit arrangement for the formation of the actual value of the current in a primary input circuit. Inrush currents are suppressed within an optimally-broad range of current by providing an electronic switch in the circuit arrangement which forms the actual value of the current, the electronic switch being inhibited during initial power peaks of the current flowing through a current sensor in the primary input circuit.