Abstract: This invention is a diode defect detecting device including a current detector for detecting the primary current of a transformer, a comparator for comparing the detection current detected by the current detector with a current reference and outputting a reset signal if the detection current is larger than the current reference, an oscillator for generating a clock signal, a flip-flop circuit for receiving a set signal on the basis of a front and an end edge of the clock signal generated by the oscillator and receiving the output reset signal from the comparator, a polarity changing circuit for outputting a polarity changing signal for changing the polarities of the plurality of diodes on the basis of the output clock signal from the flip-flop circuit, and a determination circuit for calculating, in order to detect malfunctions of the plurality of diodes, any impedance change on the secondary side viewed from the primary side of the transformer on the basis of the pulse width of each polarity of the output cl

Abstract: The isolation operation of a non-utility generation system (7) interconnected to a power system enable to be reliably detected in the non-utility generation system, providing a transfer breaker. When the frequency change rate of the non-utility generation system (7) has a positive value, the advanced reactive power of the non-utility generation system (7) is increased. When the frequency change rate of the non-utility generation system (7) has a negative value, the delayed reactive power of the non-utility generation system (7) is increased. Further, the gain of the power control section (9) of the non-utility generation system (7) is adjusted in accordance with the frequency change rate. As the gain is thus adjusted, the voltage of the non-utility generation system (7) changes. This change in the voltage is detected. In accordance with the voltage change, the non-utility generation system (7) is disconnected from the system power supply.

Abstract: A control equipment for a resistance welding machine for welding a material by the Joule's heat generated in the material by applying an electric power to the material, including an inverter for converting a DC voltage to an AC voltage by pulse width modulation control, a transformer having a primary winding to which the AC voltage is applied and having a secondary winding which supplies an AC current to the material, and a control unit for generating an AC current reference with a rectangular waveform of a specified frequency, comparing the AC current reference with an output current of the inverter to obtain an error, and for PWM controlling the inverter so that the error becomes zero.

Abstract: A control equipment for a resistance welding machine for welding a material by the Joule heat generated in the material by applying an electric power to the material, including an inverter for converting a DC voltage to an AC voltage by pulse width modulation control, a transformer having a primary winding to which the AC voltage is applied and having a secondary winding which supplies an AC current to the material, and a control unit for generating an AC current reference with a rectangular waveform of a specified frequency, comparing the AC current reference with an output current of the inverter to obtain an error, and for PWM controlling the inverter so that the error becomes zero.

Abstract: A protection device for an inverter which is connected to an AC power system, converts DC power into AC power, supplies the AC power to a load and includes a control circuit for detecting a phase and a frequency of an output voltage, for generating a current reference synchronized with the output voltage and for controlling the inverter such that an output current is coincident with the current reference. The protection device includes a first detection circuit for detecting that an AC output is disconnected from the AC power system based on an electrical quantity of the output voltage and for generating a detection signal based on a detection result, and a correction circuit connected to receive the detection signal for generating a correction signal to break a power balance between an output power and a power consumed by the load.

Abstract: An overcurrent protection circuit for a power transistor for generating a main current in response to a gate drive voltage generated by a gate circuit. The overcurrent protection circuit includes a current detection circuit for detecting the main current flowing in the power transistor to generate a detection voltage corresponding to the main current, and a level detection circuit connected to receive the detection voltage for generating a control current corresponding to a difference between the detection voltage and a prescribed value when the detection voltage exceeds the prescribed value. The overcurrent protection circuit further includes a current control circuit connected to receive the control current for limiting the main current by regulating the gate drive voltage based on the control current, and a drive instruction control circuit connected to receive the control current for making the main current zero by controlling the gate drive voltage to an OFF condition based on the control current.

Abstract: A method of controlling a battery car in which a motor is driven by a battery and the battery is charged with regeneration power generated by deceleration torque comprises the steps of charging a large-capacitance capacitor connected in parallel with the battery and the motor while restricting a current flowing from the battery to the large-capacitance capacitor, when the voltage of the large-capacitance capacitor is lower than a first voltage, charging the battery to a preset voltage while restricting a current flowing from the large-capacitance capacitor to the battery, when a charging voltage of the large-capacitance capacitor is increased above a predetermined voltage by the regeneration power, and driving the motor with only the charge stored in the large-capacitance capacitor, when the voltage of the large-capacitance capacitor is at least a second voltage.

Abstract: In a bridge type power converter, one of series-connected semiconductor elements of an inverter bridge is constituted by an MCT having a low-loss characteristic, or substantially constant-voltage characteristic, with a small voltage drop under conduction, and the other semiconductor element is constituted by an IGBT having a constant-current characteristic with a current suppressed in accordance with a drive signal. A failure current is suppressed by a current-suppressing effect of the IGBT and safely interrupted by turning off the MCT and the IGBT.

Abstract: This invention relates to an uninterruptible power source equipment to rectify a commercial power supply to charge a capacitor through a chopper circuit to a constant voltage, thus to utilize it as a constant voltage power source and to charge a back-up capacitor, thus to deliver a power from the battery to the constant voltage power source when the commercial power source is interrupted. The output of the constant voltage power source may be converted to an a.c. output by the inverter unit. The chopper circuit includes a reactor and a switching element responding to a control signal to effect on-off operation. The control signal is formed as a sine wave signal in phase with the commercial power source. This control signal may be applied to the inverter unit.

Abstract: This apparatus is a power converter which delivers a pulse produced based on a dc voltage to the primary side of a transformer with its polarity being changed per half cycle to take out an ac power from the secondary side thereof. By modulating the pulse width of a pulse delivered, the output power becomes adjustable. By detecting a current on the primary side of the transformer, current change rates at positive and negative half cycles are calculated. By comparing these change rates at the both cycles, magnetic deviation of the transformer can be detected. With the pulse width correcting means, pulse widths of pulse delivered at positive and negative cycles are adjusting so as to cancel such a magnetic deviation. The control for preventing magnetic deviation described above is realized as a control having a very fast response. In addition, such a control enables the transformer to be operative in a range extremely close to the range where the transformer is saturated.

Abstract: A driving circuit for an insulated gate bipolar transistor (IGBT) which has a power source, a gate voltage input circuit which supplies the voltage to a gate terminal of IGBT, a detecting circuit for detecting a collector to emitter voltage of the IGBT and an adjusting circuit for lowering the control signal.When an abnormality is detected by the detecting circuit, the adjusting circuit performs a dropping operation of the gate voltage of the IGBT immediately after the detection or after the passage of a predetermined time following the application of the ON signal to the gate.

Abstract: An overcurrent protective circuit for a modulated conductivity type MOSFET, i.e., a BIFET, which has a voltage detection circuit for detecting a voltage between the drain and source of the BIFET and a main switching circuit for lowering a voltage between the gate ad source of the BIFET and preventing the failure of the BIFET and delay of turn-on of the BIFET according to the output of the voltage detection circuit. The protective circuit produces a constant time delay before the main switching circuit becomes turned on during the initial turn-on period of the BIFET upon application of an ON-gate signal to the gate of the BIFET. The protection circuit thereby prevents, during the initial turn period of the BIFET, a situation where the main switching circuit is turned on but the BIFET is not turned on.

Abstract: Three-phase outputs of a voltage source inverter are supplied to AC input terminals of a diode bridge through reactors, respectively, and its DC outputs are clamped by a voltage of a first DC power source. The AC input terminals of the diode bridge are further connected to AC input terminals of a second diode bridge through capacitors, and its DC outputs are clamped by a second DC power source.

Abstract: In a control system for a voltage-type inverter which comprises a bridge connection of electric valves each comprising a reverse parallel connection of a semiconductor switching element and a diode, and converts a DC power to an AC power by means of PWM control, a voltage detection device is provided to detect an output voltage of the inverter. A voltage correction circuits corrects the pulse width of the pulse width modulation signal in accordance with the comparison of the detected voltage and the PWM signal. A drive circuit, which provides a dead time during which the switching elements of the electric valves connected in series with each other are concurrently non-conductive, uses the corrected PWM signal for driving the switching element.

Abstract: In a PWM control system for a voltage-type inverter which comprises a bridge connection of electric valves each comprising a reverse parallel connection of a semiconductor switching element and a diode, the direction of the current through each valve is detected, and variation in the output voltage is compensated in accordance with the result of the detection.

Abstract: A DC power source apparatus is provided including a current regulator having an electronic contactor, a transformer having a primary winding and a secondary winding. A series circuit of the primary winding and the current regulator is adapted for connection to an AC power source. The AC power source apparatus also includes a rectifier connected to the secondary winding of the transformer, output terminals of the rectifier being adapted to supply DC current to a DC load having an inductance. The AC power source apparatus further includes a simulator connected to detect an AC current flowing through the series circuit for simulating the DC current flowing through the DC load based on the detected AC current and a simulated time constant of the DC load to produce a simulated signal, and a controller connected to receive the simulated signal for comparing the simulated signal with a predetermined current reference to produce a phase control signal based on a comparison result.

Abstract: In a PWM voltage type inverter system comprising: a rectifier converting an AC power from an AC power source into a DC power, an inverter bridge converting the DC power from the rectifier into an AC power of a variable frequency to supply it to an AC motor, and a conduction control circuit for controlling the conduction of arms of the inverter bridge normally in a first mode wherein it operates at a frequency determined by a frequency reference signal, a control power circuit is connected to receive the power from the AC power source and the regenerative AC power from the motor and to supply a constant voltage DC power to the conduction control circuit. When power failure is detected, the conduction control circuit is switched to a second mode, wherein it operates in such a manner as to maintain the regenerative voltage at a predetermined value. With the arrangement of the invention, the motor can be kept operating over a longer period of time upon occurrence of power failure.

Abstract: A resistance welder is provided having an electronic contactor, a welding transformer coupled in series with the electronic contactor, and a secondary circuit with a welding load connected to the welding transformer. The series circuit of the electronic contactor and the welding transformer is adapted for receiving power from an AC power source. The resistance welder also includes a control device having a voltage detector coupled to detect a voltage across the electronic contactor for producing a first signal according to the detected voltage, a delay circuit coupled to receive a primary voltage across the welding transformer for delaying the primary voltage by a value determined by a first time constant thereof to produce a voltage signal, a switch coupled to receive the first signal for resetting the delay circuit according to the first signal, and a gain control circuit coupled to receive the voltage signal for controlling a transmission gain of the voltage signal to produce a gain controlled signal.

Abstract: In a commutation control device for a current type inverter, a device for detecting voltage of a commutation capacitor and a device for controlling a charging interval of the capacitor are provided. The voltage detecting device includes a comparator, while the charging interval control device includes a timing pulse generator, a circuit for delaying a pulse delivered from a pulse generator, and a timing signal generator which delivers a timing signal adapted to control a discharge interval of the commutation capacitor for restricting the voltage thereof in a predetermined range.

Abstract: In an inverter control device having a circuit for controlling the inverter in a pulse-width modulating mode, there are provided a circuit for controlling the inverter in an instantaneous mode, a detector for detecting the operating frequency of the inverter, and a mode transfer switch which selectively connects either one of the outputs of the PWM control circuit and the instantaneous control circuit depending on the operating frequency of the inverter detected by the detector.