Abstract: A protection circuit for preventing non zero-voltage switching of a lamp resonant output circuit driven by upper and lower half-bridge switches. The protection circuit includes a sense resistor disposed between the lower half bridge switch and ground for developing a voltage corresponding to the current flowing through the lower switch. A comparator compares the voltage developed across the sense resistor against a fixed reference voltage and generates an output indicative of a non zero-voltage switching condition when the voltage across the sense resistor exceeds the fixed reference voltage. A latch is connected to the output of the comparator and generates a latch output signal which disables the generation of drive signals to the upper and lower switches in the event of a non zero-voltage switch condition.

Abstract: The present invention relates to a device for limiting transient variations of a voltage for supplying a load from a dc/dc converter, including an input terminal, that receives the voltage provided by the converter, and connected to an output terminal of the device connected to the load; a first power transistor connected between a supply voltage of the converter and the output terminal; a second power transistor connected between the output terminal and the ground; and means for linearly and individually controlling each power transistor in case of an abrupt variation of the load.

Abstract: In a method for the drive of a number of coupled output stages drive signals for the output stages are generated. Given an over-voltage condition in one of the output stages, the output stage affected by the over-voltage condition is switched into a charge output mode for a limited time duration and at least one other output stage is switched into a charge pick-up mode for a limited time. This method is utilized in the operation of a control module and of a power amplifier, and achieves a charge compensation or balancing or equalization between the output stages with very little circuit-oriented outlay.

Abstract: A control system for a power conversion system, composed of at least one voltage source type converter and a transformer.

Abstract: A method and control circuit for an electronic switch, and more particularly the high side switch in a bridge circuit. Control is established by continuous and/or the combination of continuous and pulsed signals. Fail safe undervoltage protection is provided for the high side switch based on the adequacy of both high side and low side control voltages.

Abstract: The MOSFETs or IGBTs of respective arms of an electronic inverter are in series with SCRs or TRIACs triggered into conduction during intervals of intended conduction of the respective MOSFETs or IGBTs connected to the high level rectifier terminal. The piloting of the SCRs or TRIACs is effected from the piloting of the MOSFETs or with delay or in a conditional manner. The circuit eliminates the effective transience on the inverter output.

Abstract: The present invention comprises a circuit for generating a large-amplitude oscillating voltage. The circuit includes a power supply means for providing an input voltage and a power supply switching means including a solid state relay (SSR) connected to the power supply means for switching on and off the power supply means. The circuit further includes an voltage oscillating means connected to the power supply switching means to be activated by the input voltage and a voltage regulating means connected in series between the power supply switching means and the voltage oscillating means for regulating the input voltage. The circuit further includes a gate driver means connected in parallel between the power supply means and the voltage oscillating means for generating a driving voltage to the voltage oscillating means for generating the large-amplitude oscillating voltage when the solid state relay is switched on.

Abstract: An "H" type amplifier circuit uses at least two current mirrors for alternately feeding current into the load in one direction and the other direction. In order to accelerate the turn-on of the current mirrors, a capacitance is associated with each of the two current mirrors. Each capacitance is alternately coupled in parallel with the input of its associated current mirror when this current mirror delivers current, and is coupled to the supply voltage terminals when this current mirror delivers no current. The operation is effected by means of a set of switches.

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: A neutral point clamped (NPC) inverter control system including a DC power source to output DC voltage having a neutral point, an NPC inverter to convert the DC voltage into AC voltage in three phases through a PWM control, a mode selecting unit to decide a first and a second PWM modes by comparing amplitude of voltage reference with a prescribed value that is defined by a minimum pulse width, a first voltage reference conversion means to add a prescribed bias value at which a polarity changes to positive/negative within a fixed period to secure the minimum pulse width to voltage references in respective phases in a first PWM mode, a second voltage reference conversion means to fix the voltage reference in one phase by a value that secures the minimum pulse width when voltage reference in one phase is smaller than a prescribed value that is defined by the minimum pulse width in a second PWM mode and correct voltage references of other two phases so as to make line voltage to a value corresponding to the volta

Abstract: A circuit for powering a two-phase AC induction motor. The circuit generates a first signal of the form Vdc+A sin(2.pi.ft-0.degree.) and a second signal of the form Vdc+A sin(2.pi.ft-90.degree.). The first signal is input to a first error amplifier along with a first sampled difference signal from the motor. The second signal is input to a second error amplifier along with a second sampled difference signal from the motor. The outputs from each of the first and second amplifiers is input into a first comparator and a second comparator along with a sawtooth waveform to create a first sinusoidally modulated square wave signal and a second sinusoidally modulated square wave signal. The first and second sinusoidally modulated square wave signals are fed to driver circuits which in turn control an H-bridge circuit for powering the motor from a DC bus.

Abstract: A converter circuit arrangement is disclosed. As a result of the fact that GTOs are hard driven, reverse-parallel connected diodes have a reverse current response dV/dt of 2 kV/.mu.s to 10 kV/.mu.s and a low-inductance freewheeling circuit is provided between the DC voltage source and the GTOs, the GTOs and the reverse-parallel connected diodes can be operated without a protective circuit.

Abstract: To protect a switching device having a possible open-circuit failure condition, an arrangement is featured in which a thyristor is connected in parallel with the main current-carrying terminals of the switching device to be protected. The thyristor is connected so that the forward current direction of the thyristor is the same as the normal current direction through the main terminals of the switching device. The arrangement provides for the thyristor to present an irreversible effective short-circuit when its normal parameter ratings are exceeded. The protection arrangement is particularly suitable for insulated-gate bipolar transistors (IGBT's) and preferably employs a pressure-packaged asymmetrical thyristor (ASCR) as the protection thyristor. The ASCR should be selected to withstand the normal (snubber-limited) dV/dt of the voltage across the switching device.

Abstract: A converter circuit arrangement is specified in which actively controllable current and voltage rise limiting means are provided in parallel with a semiconductor switch. These means also take over the function of a reverse-connected parallel diode and essentially comprise a bipolar transistor which is driven by a control circuit.

Abstract: A control apparatus for controlling motors of an air conditioner comprises a converter circuit having switching circuitry for converting AC power to DC power and setting an input voltage of an input alternating current waveform to a sine wave of the same phase as that of an input voltage, first and second brushless motors for driving a compressor and a blower, first and second inverter circuits for converting the converted DC power to AC power and supplying AC power to the first and second brushless motors, and a microcomputer for controlling the compressor and the blower of the air conditioner. The microcomputer is constructed in such a manner that input and output operations which are necessary to control the air conditioner are executed for input and output circuits, thereby controlling at least the compressor and the blower of the air conditioner.

Abstract: An arrangement for driving a power control element of a drive unit of a motor vehicle is proposed and the arrangement has a full-bridge output stage. A direct-current motor is arranged in the bridge diagonal and the current through the direct-current motor is limited to at least one preadjusted value in that the clocked drive signals are interrupted when the preadjusted value is exceeded.

Abstract: A normal-direction mode which switches on first and fourth switches and in a mutually diagonal relationship of an H-type bridge circuit and switches off second and third switches also in a mutually diagonal relationship of the bridge circuit is executed for an on-duty time of an opening-degree command signal, and a reverse-direction mode which switches off the first and fourth switches and switches off the second and third switches is executed for an off-duty time of the opening-degree command signal. During normal operation, conduction of current to the H-type bridge circuit 70 and a coil is constantly performed irrespective of a degree of opening of a valve to be adjusted, and in a case where conduction is interrupted, it can be presumed that a broken wire has occurred in the H-type bridge circuit or coil, and determination of a broken wire can be made.

Abstract: The accident detection circuit of the present invention is such that in a voltage-type self-excited power converter composed of anode reactors 13 and 23 connected in series, respectively, to power semiconductor elements 11 and 21 of self turn off type connected in series, there are provided anode reactor voltage direction-detecting circuits 16 and 26 which detect, respectively, that the voltage in the direction generated in the anode reactors 13 and 23 exceeds a predetermined value when the current flowing in the direction of from the anode to the cathode of the each element 11, 21 increases, anode current direction-detecting circuits 17 and 27 which detect, respectively, that the current flows in the direction of from the anode to the cathode of the each element 11, 21, delay circuits 18 and 28 which delay, respectively, the output signal of each arm current direction-detecting circuit by a certain period of time, and AND circuits 19 and 29 which designate the output signal of the each anode reactor voltage

Abstract: A pulse-width modulated (PWM) circuit applies voltage to a load with high fidelity. The circuit includes switches connected in series with inductors, the inductors being magnetically coupled to other inductors connected to the gates of the switches. The arrangement of inductors and the magnetic coupling causes the turn-on of one switch to assist in the turn-off of the other switch. A pair of diodes connected across some of the inductors assures that the magnetically coupled inductors do not assist the switches to turn on. The result is a circuit which effectively eliminates the problem of "shoot through" current, without providing a "dead time" in the switching scheme, and thus without substantial power losses. The circuit can therefore be used in audio amplification, and in other applications requiring high fidelity.

Abstract: A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Abstract: A power converter including a snubber circuit which is smaller and regenerates more energy than a conventional snubber circuit. A plurality of self-quenching semiconductor switching elements are connected in series across a power supply. A capacitive element is connected to the switching elements, and is charged to more than the voltage of the power supply by a snubber action due to operation of any of the switching elements. The charge stored in the capacitive element is then regenerated to the power supply. The capacitance of the capacitive element can be almost as small as a minimum required capacitance, and can be as small as one-tenth of the capacitance required in a conventional snubber circuit, thereby providing a power converter which is smaller and has a smaller snubber loss than a conventional power converter.

Abstract: A control circuit for an H-bridge circuit comprises a single capacitor, a charge/discharge circuit for charging/discharging the capacitor in response to a control command signal, a voltage detector circuit for detecting a voltage appearing across the capacitor and a hold circuit for holding the control command signal in response to of a predetermined voltage detected by the voltage detection circuit. Charge and discharge of the capacitor is controlled in dependence on changes in the control command signal to thereby prevent occurrence of a through-current flow in the H-bridge circuit while allowing the bridge circuit to be changed over to the operation state indicated by the control command signal after lapse of charge/discharge period. The control circuit for the H-bridge circuit can be implemented in a miniaturized size with high reliability of operation while decreasing the number of elements attached externally even in the case where the control circuit is implemented in the form of an integrated circuit.

Abstract: The safety control device with digital input and analog output, is intended to deliver a mean output power above a specified threshold when two binary input sequences which are complementary or in phase opposition are applied to the input and an output power appreciably below the threshold in all other cases. It comprises a primary voltage source (18) supplying a cascade of several modules (16.sub.1 , . . . , 16.sub.k) each having an AC converter bridge and a rectifier, each branch of the AC converter bridge being controlled by one of the sequences.

Abstract: A high voltage direct current power supply having feedback control and a tection circuit for maintaining a controlled, stabilized output voltage. An oscillator is coupled to a transformer which in turn is coupled to a voltage multiplier. A feedback control is coupled to the transformer and the voltage multiplier which provides feedback to the transformer for maintaining an accurate, stable output voltage. Coupled to the feedback control is a protection circuit which prevents the output voltage from exceeding a predetermined output voltage. Additionally, the protection circuit shuts down the power supply if a short circuit occurs at the output. In one embodiment, the voltage multiplier is comprised of a plurality of voltage doubler diode and capacitor pairs. The feedback control is comprised of a comparitor and a buffer which drives a transistor coupled to the primary of the transformer, which acts as a feedback loop. The protection circuit includes a J-K flip-flop.

Abstract: A voltage boosting power supply, wherein a commercial power supply of 100 volt a.c., for example, is used as its primary power source, the input from the power source is accumulated in a capacitor and the accumulated power is then converted into a boosted a.c. power for delivery by means of an invertor, and which is provided with a storage battery as a preliminary power source for protection against power failure and arranged to disconnect the a.c. power supply from the capacitor and, instead, connect the battery across the capacitor through a high frequency switching element by switch means which operate in response to a power failure signal from a power failure detector. Accordingly, the output voltage of the battery is boosted by the capacitor and then applied to the invertor and, therefore, the output voltage can be raised without increase of the capacity of the battery and consequent increase in the size and weight of the device.

Abstract: A power converter including a snubber circuit which is smaller and regenerates more energy than a conventional snubber circuit. A plurality of self-quenching semiconductor switching elements are connected in series across a power supply. A capacitive element is connected to the switching elements, and is charged to more than the voltage of the power supply by a snubber action due to operation of any of the switching elements. The charge stored in the capacitive element is then regenerated to the power supply. The capacitance of the capacitive element can be almost as small as a minimum required capacitance, and can be as small as one-tenth of the capacitance required in a conventional snubber circuit, thereby providing a power converter which is smaller and has a smaller snubber loss than a conventional power converter.

Abstract: A closed loop pulse width modulator (PWM) inverter corrects for variations and distortion in the output AC voltage waveform caused by non-linearities of the switching devices or changes in the DC link voltage. A signal is generated that is a volt-seconds representation of the voltage error between a voltage command and the actual AC output voltage of the PWM inverter. The volt-seconds error signal becomes a controlling means in the closed loop of the PWM inverter to regulate the output AC voltage of the PWM inverter. Another signal that represents changes in the DC link voltage also modifies the voltage command signal. The system will compensate for the non-linear behavior of the PWM inverter due to deadtime, minimum on-times and off-times, and DC link voltage variations and voltage drops across the switching devices, and will also allow the operation of the inverter in a linear fashion for the region of operation when one or more of its phases are saturated, i.e., either full on or full off.

Abstract: The present invention provides an apparatus for and a method of compensating an output voltage error of an inverter that changes direct current (DC) power into alternating current (AC) power. More specifically, the present invention provides an apparatus for and a method of compensating for an output voltage error by detecting the polarity of output current from an inverter used to change DC power into AC power. In accordance with one embodiment of the present invention, a current detector is used to detect the output current of the inverter circuit. A polarity discriminating device, receiving the detected output current, sets a threshold current value that is to be used to accurately determine the polarity of the output current. As the output voltage error has the same phase but is opposite in polarity relative to the current output by the inverter, an accurate detection of the output error can be made by accurately detecting the output current polarity.

Abstract: An inverter apparatus and an inverter controlling method for judging a P-N impedance fault, a ground fault or a transistor fault by respective predetermined judging circuits according to either a voltage developed across a smoothing capacitor or the rate of change in the voltage while the smoothing capacitor is being charged. The charging of the capacitor is carried out via a resistor circuit or before the resistor circuit is short-circuited by a relay.

Abstract: A voltage-type self-commutated conversion system including a voltage-type self-commutated power converter with a plurality of anti-parallel circuits of a self-turn-off device and a diode. DC terminals of the power converter are connected to DC bus lines of the voltage-type self-commutated conversion system. The voltage-type self-commutated conversion system further includes a DC capacitor connected between the DC bus lines, a transformer connected between an AC system and AC terminals of the power converter and a control circuit for controlling the power converter.

Abstract: In a multi-series inverter arrangement comprising a DC circuit including a neutral point output terminal and a multi-series inverter including three series connections of first through fourth GTOs, each connected in parallel with the DC circuit, the juncture of the first and second GTOs and the juncture of the third and fourth GTOs being connected to the neutral point output terminal via respective clamping diodes and the first and third GTOs and the second and fourth GTOs being on and off controlled each other in a conjugate relationship, individual gate driving circuits for the second and third GTOs being designed to provide a larger gate current, in particular, a larger wide width gate forward current to the corresponding GTOs than that provided by individual gate driving circuits for the first and fourth GTOs to the corresponding GTOs.

Abstract: A multi-level inverter apparatus comprises: first and second GTOs connected in series between a positive electrode of a D.C. power supply having a mid-potential point and an output terminal, and third and fourth GTOs connected in series between a negative electrode of the D.C. power supply and the output terminal. First and second reactors cooperate with the first and second GTOs and the third and fourth GTOs so as to form a positive and negative arms, respectively. A first diode is connected between one end of the first reactor and the mid-potential point of the D.C. power supply in forward direction with respect to the output terminal, while a second diode is connected between one end of the second reactor and the mid-potential point of the D.C. power supply in backward direction with respect to the output terminal. First to fourth series connections, each including a diode and a capacitor connected in series to each other, are connected in parallel with the first to fourth GTOs, respectively.

Abstract: An electrical power converter having a phase converter constituted by positive side semiconductor switching elements connected in series and negative side semiconductor switching elements connected in series which converts a DC voltage to an AC output phase voltage having at least three potential levels, resulting in three possible modulation modes: dipolar, partial dipolar and unipolar. Dipolar modulation is realized by alternating positive and negative output pulses. Unipolar modulation is realized by output pulses having only the same polarity as the corresponding fundamental modulation wave. Transition is accomplished via partial dipolar modulation which is realized by alternating positive and negative output pulses in a first period of a half cycle by outputting alternating positive and negative pulses and in a second period by outputting pulses having only the same polarity as the corresponding fundamental modulation wave.

Abstract: Free wheeling diodes are protected against an overcurrent. When counter electromotive forces E.sub.VU and E.sub.WU established in a tri-phase motor cause regenerative currents I.sub.V1 and I.sub.W1 to flow to transistors Q4 and Q6, and to a protection diode D2, it is decided that the protection diode D2 is in overcurrent state. In response to the decision, the transistors Q4 and Q6 are turned off, which allows that regenerative currents I.sub.V2 and I.sub.W2 flow in protection diodes D3 and D5 because of the counter electromotive forces E.sub.VU and E.sub.WU. The energies of the regenerative currents I.sub.V2 and I.sub.W2 are regenerated at a capacitor C. Thus, since a regenerative current which once passed by only one protection diode is divided into two current flows into two protection diodes, the overcurrent state is terminated.

Abstract: A method and apparatus for limiting current through a switching device supplying current to a load. A control evaluates a model representing the switching device temperature as a nonlinear function of current and time. The model compares the temperature of the switching device to a maximum allowable temperature. The current limit is defaulted to peak current; and in response to the model detecting a temperature in excess of the maximum allowable temperature, a nominal current limit is set. The current limit reset to peak current after the model detects a switching device temperature a predetermined magnitude below the maximum allowable temperature.

Abstract: The power conversion system of this invention comprises line-commutated power converting means in which a line-commutated power conversion circuit that performs line-commutated commutation and a coupling diode are coupled to form a DC circuit and for converting DC power into AC power or AC power into DC power. Further, the system comprises self-commutated power converting means, in which a self-commutated power conversion circuit is coupled to the coupling diode in order to form a DC circuit and for reducing reactive power, or the reactive power and harmonics generated by the line-commutated converting means. Accordingly, their respective strengths can be made use of and their mutual weaknesses can complement each other.

Abstract: A conversion apparatus including a plurality of high-speed switching devices, each being operable in latch type operation and non-latch type operation and a power source for supplying a first current to the high-speed switching devices, thereby forming a current path of the high-speed switching devices. The high-speed switching device is turned off after changeover from the latch type operation to the non-latch type operation. The conversion apparatus further includes a current regulation circuit provided in the current path for regulating a second current flowing through the current regulation circuit after the second current has reached a prescribed value. In case of overcurrent malfunction, the high-speed switching device is changed from the latch type operation to the non-latch type operation, and then is caused to be turned off while the current regulation circuit regulates the second current.

Abstract: In a two-point or three-point inverter, a feedback circuitry is provided, which is disposed in parallel with a feedback capacitor (CR), and essentially include a semiconductor valve (SR) and a transformer (TR). As a result of switching the semiconductor valve (SR) once, the energy of the protective-circuit reactances, which have been stored in the feedback capacitor, is fed back into the link-circuit voltage source by the transformer. The arrangement according to the invention is distinguished by a high efficiency, accompanied at the same time by high turn-on/turn-off frequency of the semiconductor switch.

Abstract: A multi-step, alternating current power supply that provides for a failed-operation redundancy safety system that compensates for a short-circuited power switch and maintains an AC regulated output voltage without introducing undesirable harmonic components. The firing and logic controller 33 senses a short-circuited power switch 46 within an inverter bridge 32 and disables all complementary power switches 48 within the faulted bridge and enables the remaining power switches 50 in the faulted bridge. The firing sequence is adjusted for the remaining healthy power switches 52 by increasing the phase shift of the individual waveforms 54. The generator voltage is increased as required to maintain the desired AC voltage output level 56.

Abstract: A power converting apparatus controls switching of self turn-off type semiconductor devices so as to perform power conversion. The apparatus comprises a plurality of switch units each having first and second self turn-off type semiconductor devices, first and second diodes, and a capacitor. The cathode of the first self turn-off type semiconductor device is connected to the anode of the first diode, and the cathode of the second diode is connected to the anode of the second self turn-off type semiconductor device. The capacitor is connected between a common junction between the cathode of the first self turn-off type semiconductor device and the anode of the first diode and a common junction between the cathode of the second diode and the anode of the second self turn-off type semiconductor device.

Abstract: Power supplies for generating a stream of electrical pulses in which successive pulses have opposite polarities. The pulses are formed and outputted from pulse generating circuitry which has two complementary pairs of MOSFETs arranged in an H-bridge configuration. Other major components of the power supply are voltage regulators for supplying positive and negative operating pulses with selected, precisely controlled voltages to the driver and watchdog circuits for disenabling the pulse outputting circuitry if: the frequency of the operating pulses deviate from a selected range, the widths of the operating pulses exceed a selected maximum, extraneous pulses are present, or the voltage of the operating pulses falls below or exceeds selected maximums. In one important application, the power supply is employed to drive the emitter of an infrared radiation source.

Abstract: In an inverter with overload current projection, a half-bridge is divided in module form into two quarter-bridge branches. Disposed in the latter are a gate turn-off semiconductor component (7, 8), a freewheeling diode (9, 10) situated opposite with respect to a center point and a blocking capacitor (11, 12) in parallel with freewheeling diode (9, 10) and turn-off semiconductor component (7, 8). A measuring resistor (R1, R2) and a current-limiting component (L1, L2) are provided between a load terminal (3) of the bridge circuit and the center points of the quarter-bridge branches. The load current can be determined in a transient-free manner with the measuring resistors.

Abstract: A MOSFET output driver circuit is protected from overstress caused by commutating currents. The MOSFETs are protected by employing a gate control circuit and a small inductor in series with the sources of the MOSFETs. The circuit limits the rate of change of current that reverse biases a MOSFET's drain-source diode. The circuit is applicable to totem-pole and bridge configurations.

Abstract: The addition of an external commutating inductor and two clamp diodes to the phase-shifted PWM full-bridge dc/dc converter substantially reduces the switching losses of the transistors and the rectifier diodes, under all loading conditions. We give analyses, practical design considerations, and experimental results for a 1.5-kW converter with 60-V, 25-A output, operating at 100-kHz clock frequency and 95% efficiency.

Abstract: A power converting apparatus comprises self-commutated converter, fault current restricting device, fault detector, and cutoff circuit. Self-commutated converter converts AC power supplied from an AC power system into DC power and supplying the DC power to a common DC circuit, and for converting DC power supplied from the DC circuit into AC power and supplying the AC power to the AC power system. The fault current restricting device is inserted between the self-commutated converted and the DC circuit, and includes a diode provided to permit a DC circuit current to flow from the self-commutated coverter to the DC circuit, and a series circuit having a reactor and a DC power supply and connected in parallel to the diode. The fault detector detects a fault current generated when self-commutated converter is short-circuited. When the fault detector detects a short circuit occurring in self-commutated converter, the cutoff circuit cuts off power supply to that self-commutated converter.

Abstract: An inverter control device that controls a self-commulated inverter connected to an AC power system via a three phase transformer and in so doing suppresses DC magnetization in the three-phase transformer. The device includes a current DC component detecting circuit for detecting the current DC components contained in at least two of the three phase output AC currents of the inverter and a DC magnetization suppressor signal generating circuit for producing two correcting signals from the current DC components. The two correcting signals are used to balance in amount the three voltage DC components contained in the three phase output AC voltage of the inverter, respectively. An output reference correcting circuit is provided to correct two of first output references in accordance with the two correcting signals and output three second references including the two corrected values and one of the first output reference.

Abstract: This invention consists of a power conversion device wherein a circuit comprising semiconductor power elements and fuses connected in series with these, and feedback diodes connected in antiparallel with said semiconductor power elements is connected as a bridge, the A.C. terminals of said bridge circuit are connected to an A.C. power source, and the D.C. terminals are connected to a D.C. power source provided with a capacitor, characterized in that said feedback diodes are connected in antiparallel with the series circuits of said semiconductor power elements and fuses.By means of the layout described above, the fuses are prevented from melting when a D.C. short-circuit occurs, since the current that flows from the A.C. terminal to the D.C. power source on D.C. short-circuiting flows through a feedback diode or a bypass diode, and not to the fuses.

Abstract: In a control apparatus for controlling the firing timing of each of thyristor valves constituting a thryistor bridge by use of at least two series of control systems, a bypass-pair control circuit for thyristor bridge includes a circuit for detecting the conduction states of the thyristor valves, and a circuit for determining a conductive valve at the time of bypass-pair operation in accordance with a result of detection of the conduction state of each thyristor valve.

Abstract: With respect to their connection to snubber capacitors (C1, C2), a discharge resistor (12) connecting these snubber capacitors, and a link capacitor bank (3), inverter circuits with GTO thyristors (T1, T2) connected in series have parasitic leakage inductances which limit the level of the permissible link direct voltage. In order to reduce the leakage inductances, the snubber capacitors (C1, C2) are surrounded by effectively conducting capacitor covers (17). Sheet-metal shielding covers are fitted over the two ends of the discharge resistor (12). Parallel and series connected capacitors of the link capacitor bank (3) are connected to the positive/negative terminals (23, 24) of the GTO thyristors (T1, T2) in the middle of a heat sink connecting strainer (33), the supply leads being guided essentially parallel and the capacitors being arranged in opposite planes.

Abstract: A protection device for a power converter utilizing GTO thyristors. A reactor is connected in series with the switching elements to suppress the current change rates. A capacitor is connected to the reactor by way of a coupling diode to receive and store energy from the reactor. An overvoltage prevention device is connected in parallel with the capacitor to keep the voltage of the capacitor below a set value. A single protection device may be utilized with a polyphase converter or a multiplex converter, thus providing a compact low cost protection device.