Abstract: A DI-circuit breaker device includes a summation current converter for detecting fault currents in a phase conductor and a neutral conductor, and a detection device for detecting fault states of a protective ground conductor. The detection device detects the presence of a phase voltage on the protective ground conductor as a fault state. The detection device has a capacitive sensor which, when touched by a user, forms an electric capacitor with an impedance relative to ground potential. The detection device further has evaluating electronics adapted to determine a phase position by connecting the sensor to the phase conductor and, separately therefrom, to the neutral conductor. The evaluating electronics determine the absence of a phase voltage on the protective ground conductor when there is no voltage between the neutral conductor and the protective ground conductor when phase is present at the phase conductor. Further, a corresponding operating method is described.

Abstract: Disclosed is an aircraft sensor fault detection system. The system includes a sensor system having a sensing apparatus to measure a parameter of an environment and a measurement circuit coupled to the sensing apparatus. The system includes a source of alternating current connected to the sensor system. The system further includes an alternating current measurement system that measures alternating current passing through the sensor system and indicates an error when a threshold based on a change in impedance of the sensing apparatus is exceeded.

Abstract: A neutral grounding resistor fault protection arrangement. The fault protection arrangement may include a neutral grounding resistor, the neutral grounding resistor comprising a ground end and a non-ground end; a sense circuit, coupled to the non-ground end of the neutral grounding resistor; and a neutral grounding monitor, coupled to the non-ground end of the neutral grounding resistor, the neutral grounding monitor comprising an injection signal generator, the injection signal generator arranged to generate a frequency of 240 Hz or greater.

Abstract: An electronic protection device (1) for a LV electric line (100) including one or more conductors (P, N), comprising: one or more pairs of electric contacts (2) electrically connectable with corresponding conductors of said electric line and adapted to be mutually coupled or decoupled, said electric contacts being coupled when said protection device is in a closed state and being decoupled when said protection device is in a tripped state or open state; a control unit (3) comprising a controller (31) including data processing resources, said controller being capable of testing the operating conditions of said electronic protection device; a signalling arrangement (7) including one or more signalling devices (71) driven by said controller. Said signalling arrangement comprises a first signalling device (71) adapted to provide light signals (L1, L2, L3) indicative of the operating conditions for said electronic protection device, when said electronic protection device is in a closed state.

Abstract: Plug-on ground fault modules are configured with a housing and at least one ground fault terminal. The at least one ground fault terminal can be a rigid or semi-rigid member that is configured to slidably engage a circuit breaker terminal. The modules also include aground fault circuit coupled to the ground fault terminal and at least one printed circuit board in the housing with components of the ground fault circuit including at least one solenoid assembly coupled thereto with a respective magnetized or magnetic plunger member residing on or adjacent thereto, and at least one current transformer. The modules also include at least one collar assembly residing in the housing spaced apart from the solenoid assembly and plunger member that is arranged to be able to engage a lever in the circuit interrupter to delatch the circuit interrupter.

Abstract: Current transformer circuit systems and methods dynamically switch a load. The current transformer circuit includes a current source circuit including at least one current transformer to produce a current output wave. A burden circuit includes at least one burden resistor and a voltage sensor, at least a portion of the current output wave to be passed through the burden resistor, and the voltage sensor to sense a voltage across the respective at least one burden resistor. A switch circuit includes at least one switch, the switch circuit coupled to the burden circuit. A microcontroller circuit includes a microcontroller, the microcontroller circuit coupled to a power circuit and the switch circuit, the microcontroller being configured to control the switch circuit to dynamically switch a secondary loading of the at least one current transformer between the burden resistor and a low resistance load.

Abstract: An intelligent circuit breaker electrically is capable of being actuated and interfacing with a conventional circuit breaker. The intelligent circuit breaker includes a wireless transceiver for communicating with other intelligent circuit breakers, a breaker controller, memory, and a display. The memory may be used to temporarily store data of interest regarding the intelligent circuit breaker's status, power consumption, operating history, and the like. The intelligent circuit breaker may advantageously be constructed in a form factor which is compatible with standard circuit breaker panels.

Abstract: The line power and neutral conductors for a circuit interrupter such as a miniature circuit breaker, using ground fault sensing via a current transformer, are arranged as a rigid conductor formed from a flat plate and surrounding and holding an insulated flexible conductor when passing through the Ground Fault Interrupter current transformer. The rigid conductor can provide a shaped current path to maximize the effectiveness of the current transformer.

Abstract: The present disclosure relates to directionality of events on line sensors for power lines. In an embodiment, a line sensor may include phase detection circuitry that detects a feature of an operating parameter of a power line prior to an occurrence of an event. The phase detection circuitry may provide a time associated with the feature. The line sensor may include sensor circuitry that sends an activation signal. The line sensor may include a controller that, upon receiving the activation signal, measures samples of the operating parameter. The line sensor may determine a relative direction of the event based on the plurality of times detected prior to the event and the measured samples of the operating parameter.

Abstract: An alternating-current voltage detection circuit for detecting an alternating-current voltage from an alternating-current power source according to one or more embodiments may include: a rectification circuit that performs full-wave rectification on an alternating-current voltage from the alternating-current power source and supplies a rectified output to a load; a series circuit comprising a first capacitor and a second capacitor electrically connected in series between one end of the alternating-current power source and the ground terminal of the rectification element; a discharge circuit that causes the second capacitor to discharge such that an absolute value of dv/dt voltage does not reach a predetermined voltage, wherein the second capacitor is electrically connected to the ground terminal side of the rectification element; and a predetermined period generator that outputs a signal after an elapse of a predetermined period of time from stoppage of a discharge operation of the discharge circuit.

Abstract: The present invention is directed to an electrical wiring device that includes an automatic test circuit configured to commence an automatic test at a predetermined time such that a test current propagates on a test conductor. The sensor assembly provides a sensor test output responsive to the test current only if both the differential transformer and the grounded neutral transformer are operative. A fault detector circuit is configured to generate a test detection signal in response to the sensor test output only if the fault detector circuit is operable and the at least one power supply is substantially charged. A device integrity evaluation circuit includes a timer that effects a tripped state when a time measurement exceeds a threshold, the test detection signal resetting the time measurement when properly wired before the time measurement exceeds the predetermined threshold but does not reset the time measurement when miswired.

Abstract: Implementations of fault detection circuits may include a first current transformer coupled to a second current transformer, a positive feedback circuit including the first current transformer, the second current transformer, a first switch, and one of a comparator, an amplifier, and an inverter. The circuit may also include a plurality of logic gates that may be coupled with the positive feedback circuit. The positive feedback circuit may be configured to oscillate upon detecting a ground neutral fault and to send a fault signal to the plurality of logic gates. The plurality of logic gates may be configured to analyze the fault signal and open the first switch. The plurality of logic gates may be further configured to identify whether the fault signal represents one of a true fault or a noise fault by analyzing the output of the positive feedback circuit after the first switch has been opened.

Abstract: A leakage current protection plug includes a body formed by a top cover and a base, a moving assembly disposed in the body, and output wires. The moving assembly includes a control circuit board, and a detector assembly and a trip assembly disposed on the control circuit board, wherein power input insertion plates and power output moving contact arms are assembled with the moving assembly. Each output moving contact arm is formed integrally and fixed to the detector assembly, and the output ends of the output moving contact arms are directly connected to the output conductor wires. The device has a simple overall structure and can be reliably assembled. By using integrally formed output moving contact arms to directly couple the input and output, it improves the accuracy of the leakage current detection parameters, reduces internal transfers and solder points, and reduces the size and cost of the plug.

Abstract: An electric leakage detecting device using a middle point grounding method in which detection current flowing in the resistors as well as sensitivity for detecting current is kept low.

Abstract: An arc fault detection arrangement for a DC electric bus, the DC electric bus having a plurality of electric lines adapted to electrically connect a source section and a load section of an electric apparatus, the arc fault detection arrangement including an arc fault detector adapted to receive and process detection signals indicative of AC currents flowing along the electric lines characterized in that it includes a current sensing device. The current sensing device includes: primary winding means including a plurality of first primary winding conductors adapted to be electrically connected in series with source portions and load portions of corresponding first line conductors of the electric lines; secondary winding means magnetically coupleable with the first primary winding means, the secondary winding means comprising at least a first secondary winding conductor electrically connected with the arc fault detector to provide the detection signals to the arc fault detector.

Abstract: The line power and neutral conductors for an arc fault sensing circuit interrupter such as in a miniature circuit breaker are arranged as a rigid conductor surrounding and holding an insulated flexible conductor when passing through the Ground Fault Interrupter current transformer. Voltage metering takes place across the rigid conductor to enable arc fault detection and ground fault detection in the miniature circuit breaker within the space of a single current transformer.

Abstract: Systems, methods, and devices for aircraft power distribution include a bipolar high voltage direct current source component; an electrical loading component capable of drawing electrical power from the bipolar high voltage direct current source component; a set of switching components configured to selectively couple power from the bipolar high voltage DC source component to the electrical loading and a ground fault interruption component coupled to the set of switching components. The ground fault interruption component is configured to detect a ground fault based on a sensed difference between a current flowing out of the set of switching components and back from the electrical loading component.

Abstract: A wiring device including an interrupting device, a fault detection circuit, and a testing circuit. The interrupting device electrically connects a line terminal to a load terminal when the interrupting device is in a reset condition and disconnects the line terminal from the load terminal when the interrupting device is in a tripped condition. The fault detection circuit is configured to detect a fault condition and generate a fault detection signal in response to detecting the fault condition, the fault detection signal is provided to the interrupting device to place the interrupting device in the tripped condition. The testing circuit is configured to determine a frequency of an input voltage at the one or more line terminals, perform a first test of the interrupting device at a first period of the frequency, and perform a second test of the fault detection circuit at a second period of the frequency.

Abstract: A wireless power transmitter includes a switch circuit including switches connected to a transmission resonator; a current detector configured to detect a transient current induced in the transmission resonator; and a controller configured to control the switch circuit and adjust an output of the wireless power transmitter based on an amplitude of the transient current.

Abstract: A residual current protective device for an electric circuit having at least one electrical consumer comprises a residual current determination component, a leakage current determination component and an interruption component. The residual current determination component is configured to determine an amperage difference between the amperage of a current flowing to the at least one electrical consumer and the amperage of a current flowing from the at least one electrical consumer. The leakage current determination component is configured to determine the amperage of a leakage current flowing out of the electric circuit to earth (ground). The interruption component is configured to interrupt the electric circuit if the difference between the determined amperage difference and the determined amperage of the leakage current exceeds a preset limit value.

Abstract: A system comprising: a first high voltage unit that is coupled via a high voltage supply cable to a second high voltage unit; a transformer that is configured to magnetically couple the high voltage supply cable to windings of a transformer; and a detection unit that is configured to monitor a windings signal developed in the windings of the transformer to detect a first high voltage unit arc formed within the first high voltage unit and to detect a second high voltage unit arc formed within the second high voltage unit.

Abstract: A power distribution system including a high-voltage direct current unit (HVDCU) configured to receive an amount of high-frequency alternating current (AC) input power from a power source and convert the input power into high-voltage DC power, a negative voltage distribution rail and a positive voltage distribution rail that are together configured to supply the high-voltage DC power to at least one control unit (CU) electrically disposed between the negative voltage distribution rail and the positive voltage distribution rail and the CU being configured to convert the high-voltage DC power into output power compatible with at least one load and supply the output power to the loads associated with it.

Abstract: An isolated DC power supply device that supplies direct current (DC) power via a positive electrode line, a negative electrode line, and a neutral line to which a signal is applied, the isolated DC power supply device including: an amplifying unit configured to amplify the DC power; a receiving unit configured to detect an occurrence of a ground leakage current flowing to the positive electrode line or the negative electrode line, compare a voltage of the neutral point with a voltage of the signal of the neutral line and connect the neutral line with a ground point via a coil; and an impedance adjusting circuit configured to be installed between the amplifying unit and the receiving unit and adjust an impedance in a voltage range of the signal applied to the neutral line and in a voltage range other than the signal voltage range.

Abstract: A method is disclosed providing ground fault circuit interruption protection for a pump motor which includes determining a current difference between at least two leads located on a load side of an electromechanical device, wherein the electromechanical device is configured to mechanically drive a road, and wherein the method further comprises interrupting a flow of current in response to the current difference exceeding a threshold current difference.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for assigning channels in a messaging system. An example method includes: providing a plurality of channels, wherein each channel includes an ordered plurality of messages; assigning each channel to a channel bucket to form a plurality of channel buckets, wherein each channel bucket includes at least two channels from the plurality of channels; and assigning each channel bucket to a node selected from a plurality of nodes, wherein the node includes one or more buffers for storing messages according to the order from the channel buckets of the node.

Abstract: A method is disclosed for testing a latching solenoid of a switch and a testing device for carrying out the method is disclosed. The switch includes a switching contact, formed by contact elements mechanically separated from one another when the switching contact is open; an electronic trip unit, to respectively monitor the current passing via the contact elements and test whether a current-dependent tripping condition is satisfied; and an actuator, to separate contact elements after actuation, the trip unit actuating the actuator via the latching solenoid when the tripping condition is satisfied; and an electrical energy store, to charge to a voltage before the tripping and to be discharged via the latching solenoid. After a period of time after the tripping, the voltage of the energy store is compared with a reference value and a fault signal is output if the voltage of the energy store is above the reference.

Abstract: A generator system includes a generator controller for monitoring the operation of generator cable. The generator controller is configured to receive a first signal indicative of a generator output and a first connection of a generator cable and a second signal indicative of a second connection of the generator cable. The generator controller is configured to calculate a characteristic value for the generator cable based on the first signal and the second signal and compare the characteristic value for the generator cable to a threshold value. A generator status message or a generator command is generated in response to the comparison. The characteristic value may be resistance of the generator cable.

Abstract: A system and a method for driving an electrical motor with a drive unit including a wireless transceiver. A user may wirelessly couple a user input device with the transceiver, and use a drive application to, optionally, update configuration information including drive control parameters, update application logic residing in the drive unit, and/or upload performance parameters.

Abstract: An arc fault circuit interrupter (AFCI) outlet is disclosed which detects and interrupts upstream parallel arc faults. The example AFCI outlet includes a switching element coupled between the line and neutral conductors at the outlet. The outlet also includes a voltage sensor and a current sensor. A parallel upstream arc fault is detected from a sensed voltage drop and no corresponding increase in current. On detecting the arc fault, the switching element is closed and current flows through the relatively lower resistance switching element interrupting power through the arc fault. The closed switching element results in an overcurrent condition causing an upstream conventional thermal-magnetic circuit breaker to trip.

Abstract: An arc fault circuit interrupter detector circuit including a super regenerative high frequency receiver is described herein. In one exemplary, non-limiting embodiment, a current measure component determines that a current noise signal within a circuit breaker is occurring at a particular frequency of interest. The super regenerative high frequency receiver receives the current noise signal and, via an oscillator circuit, causes the signal to ramp to a quench voltage, dissipate, and repeat. A microcontroller in communication with the super regenerative high frequency receiver measures a time period of the oscillator circuit's oscillations, and determines an amplitude of the current noise signal based, at least in part, on the time period. If it is determined that the amplitude of the input current signal at the frequency of interest corresponds to an arc fault event, a trip signal is generated to trip the circuit, quenching the arc fault event.

Abstract: Apparatuses and systems for analog/digital input architecture having programmable analog output mode are described herein. One apparatus includes a current source component to create a current source, a pulse-width modulation (PWM) control component to implement an analog output mode, wherein the analog output mode is implemented on a same input/output terminal as at least one other device mode, a dither input component to receive a dither signal, a current shunt component to create an input shunt, a resistance/thermistor input pull-up component to provide an excitation voltage, a voltage/current input scaling component to provide input prescaling, an input protection component to protect at least one port of the apparatus from damage, and an input filter component to provide filtering to high frequency noise.

Abstract: An integrated contactor/service disconnect assembly according to an exemplary aspect of the present disclosure includes, among other things, a stationary contact, a movable contact selectively movable relative to the stationary contact and a service disconnect unit configured to block the movable contact from contacting the stationary contact.

Abstract: An interface for cutting off the power supply for any fault current Id?300 milliamperes such that: Id?IPE+k·Ih where IPE represents the current returning to the power source via the protective conductor connecting the exposed conductive parts to earth and Ih (?10 or 30 milliamperes) represents the current returning to the power source by ways other than via the protective conductor or via an active conductor. Current Ih is therefore likely to travel through a person. In this way, the interface protects people and property against ground insulation faults and against certain direct contacts independently of the earth of the exposed conductive parts and of external conditions. It also protects people in the event of a failure in the protection of an area using the same earth in case of a fault.

Abstract: An electric coil device includes a terminal unit and a coil module. The terminal unit includes a block and multiple terminals. The coil module is mounted to the block and includes first and second winding cores, two first wires and two second wires. Each of the first wires has a transformer wire segment wound on the first winding core, and an inductor wire segment wound on the second winding core. The transformer wire segment of each of the first wires is electrically connected to a respective one of the terminals, and the inductor wire segment of each of the first wires is electrically connected to the respective one of the terminals, thereby achieving the functions of a transformer and a common-mode choke.

Abstract: A residual-current-operated protective arrangement includes a residual-current-operated protective device that has a core and an evaluation coil. A control device is provided that has a detection unit for detecting an electric current flowing through the evaluation coil. The residual-current-operated protective arrangement has a test winding that is inductively coupled to the evaluation coil via the core and the control device has a testing unit for impressing a predetermined test current into the test winding.

Abstract: The present invention is directed to an electrical wiring device that includes an automatic test circuit configured to commence an automatic test at a predetermined time such that a test current propagates on a test conductor. The sensor assembly provides a sensor test output responsive to the test current only if both the differential transformer and the grounded neutral transformer are operative. A fault detector circuit is configured to generate a test detection signal in response to the sensor test output only if the fault detector circuit is operable and the at least one power supply is substantially charged. A device integrity evaluation circuit includes a timer that effects a tripped state when a time measurement exceeds a threshold, the test detection signal resetting the time measurement when properly wired before the time measurement exceeds the predetermined threshold but does not reset the time measurement when miswired.

Abstract: An electromagnetic radiation detecting system within an electric system, the electromagnetic radiation detecting system comprising: a plurality of induction rings, each for surrounding one of a plurality of electric lines of the electric system; and a controller connected to the plurality of induction rings, for measuring voltages produced by the plurality of induction rings, and for indicating, from the measuring, electric lines corresponding to induction rings having non-zero sum total electric current flows, thereby indicating the electric lines as being electromagnetic radiation pollution sources.

Abstract: An electric household appliance has a low-voltage capacitive power means (10) connected to an electrical power network (3) and is designed to generate a low-voltage (S2,V2). The low-voltage capacitive power means (10) comprise a capacitive dividing circuit (28) comprising a first (30) and second input terminal (31) connected to a first and second power line (3) at a first (V1) and second (VREF) predetermined potential respectively; a first output terminal (32) adapted to generate said low-voltage enabling signal (S2); first (37) and second charge-accumulating means (38) connected between said first and second input terminal; and at least one voltage limiter (40) connected parallel to said second charge-accumulating means (38) and designed to switch from a non-conducting to a conducting state when subjected to a voltage above a predetermined breakdown voltage (VZ).

Abstract: A system for protecting an inrush resistor by determining whether an inrush relay connected in parallel with the resistor properly closes. A differential amplifier connected across the resistor produces an output signal that is proportional to the differential voltage. A control circuit determines whether the relay is open based on the output signal, and if the relay is open and the motor is running, takes remedial action to protect the inrush resistor. Alternatively, the amplifier is replaced with a slow response filter that produces an output signal that is a delayed version of a bus voltage. The control circuit determines the difference between the bus voltage and the output signal, and if it exceeds a predetermined value and the motor is running, takes remedial action to protect the inrush resistor. Remedial action may include shutting off the motor or restarting the motor to confirm improper behavior of the relay.

Abstract: An electrical power plug or receptacle with an over-temperature protection function, including a reset switch operated by a solenoid that electrically connects and disconnects the input side and output side electrical lines, and an temperature-controlled switch disposed in thermal contact with one or more electrical conductor plates on the input or output side. The temperature-controlled switch is connected in series with the solenoid between the output side phase and neutral lines. When the temperature of the temperature-controlled switch is within a normal range, the switch is open and does not form a current path with the solenoid. When the temperature is at or above a threshold temperature, the temperature-controlled switch is closed, a current flows through the switch and the solenoid between the output side phase and neutral lines, and the solenoid operates the reset switch to disconnect the input side from the output side.

Abstract: A test system for testing a sensor system includes a high-impedance resistor for forming a voltage divider with any corrosion or foreign substance that might be present between a signal conductor and a ground conductor. While a voltage is applied across the voltage divider, the voltage can be measured across the high-impedance resistor for determining whether an undesirable amount of conductance exists between the signal wire and ground. The test system also includes switching means for switching between any number of signal wires of a system undergoing testing.

Abstract: A system includes an excitation system configured to regulate one or more outputs of a power generating system. The excitation system includes data processing circuitry configured to obtain an electrical voltage measurement and an electrical current measurement associated with the power generating system, a transformer failure detection system configured to detect an abnormality associated with the electrical voltage and electrical current measurements as an indication of a possible transformer failure, and a failure detection deactivation system configured to deactivate the transformer failure detection system based at least in part on whether the abnormality comprises one of a first condition or a second condition.

Abstract: An earth clamp for testing contact voltage, comprising a measuring circuit formed of a voltage inducing transformer and a current measuring transformer, adapted to be mutually coupled by an earth conductor whose earth impedance is to be measured, a microcontroller to deliver an alternating voltage to the voltage inducing transformer and, in response, to receive a reference voltage generated in the earth conductor and an earth current iB+iF induced in the current measuring transformer, the microcontroller being configured to extract an amplitude E of the reference voltage, an amplitude IB and an amplitude IF of the earth current and a phase shift ? between the reference voltage and the loop current iB and to calculate the earth impedance Zb at a determined frequency, the microcontroller also computing the contact voltage Uc at said determined frequency by the product of the earth impedance times the amplitude IF.

Abstract: A system and a method for measuring leakage current in an electrical transmission network. The system contains a plurality of electric current measurement devices distributed along the electrical transmission network and at least one central controller. The current measurement devices measure the electric current substantially continuously or repeatedly and report to the central controller. The central controller performs analysis of the measurements of the electric current along the transmission network and calculates the leakage current.

Abstract: A power converter includes a first phase leg including a first di/dt reactor and a first control section, the first di/dt reactor and the first control section being coupled between an active line and a neutral line. The power converter also includes a first current crowbar coupled between the active line and the neutral and a controller coupled to the first di/dt reactor, the control section and the first current crowbar and configured to activate the current crowbar based on a voltage across the first di/dt reactor.

Abstract: An arc fault detector, an electrical device having the arc fault detector, and a method of controlling the electrical device. The arc fault detector includes a current detector to detect current flowing through a plurality of loads in an electrical device, a filter unit to pass current having a frequency equal to or higher than a predetermined cut-off frequency from the frequency of the detected current, a comparison unit to compare a voltage of the passed current with a predetermined threshold voltage and output a comparison signal based on a comparison result, and a controller to determine whether an arc fault has been generated by comparing the comparison signal with a predetermined reference arc fault signal, determine a load having the arc fault from among the plurality of loads, and control cut-off of power to the determined load.

Abstract: An earth fault detection circuit for detecting an earth fault between a high-voltage battery and a motor includes: an A.C. signal generation portion generating an A.C. signal; a first capacitive element between the A.C. signal generation portion and one end side of the high-voltage battery; a voltage dividing circuit dividing a voltage on the one end side of the high-voltage battery; an earth fault detection portion detecting the earth fault between the high-voltage battery and the motor based on an earth fault detection signal inputted thereto; and a second capacitive element inputting an A.C. component of the voltage, on the one end side of the high-voltage battery, which is obtained by the voltage division in the voltage dividing circuit as the earth fault detection signal to the earth fault detection portion.

Abstract: In one aspect of the invention there is provided a device comprising electrical connector means adapted releasably to connect the device to an electrical circuit overload protection apparatus of a motor vehicle, the device comprising means for measuring an amount of electrical current flowing therethrough and means for outputting from the device a signal corresponding to the amount of electrical current flowing therethrough.

Abstract: Methods and apparatus for continuous ground fault self-test are disclosed. An example ground fault detection device includes a sense coil to detect current in a line conductor and a neutral conductor, the sense coil comprising a winding influenced by a current difference between the line conductor and the neutral conductor. The example ground fault detection device also includes a current bypass to facilitate a continuous current imbalance detected by the sense coil, and a ground fault detector circuit to detect at least one of the continuous current imbalance in the sense coil or a ground fault current imbalance.

Abstract: A stored electric power discharging circuit for an inverter device includes a group of series resistors configured to be connected in parallel to a plurality of main circuit capacitors in a normal operation, a voltage stabilization circuit configured to stabilize interterminal voltages of the respective main circuit capacitor according to a divided voltage of the series resistors during the normal operation, and a control switch having a control input and configured to cut the direct connection between the series resistors at a time of power-off, thereby breaking a voltage stability state of the main circuit capacitors by the voltage stabilization circuit.