Mitsubishi Denki Kabushiki Kaisha

Hiroshi Mitsuoka

Yoshio Kimura

Masayoshi Kumano

Isamu Hosono

For suppressing an abnormal rise in the anode-cathode voltage of a gate turnoff thyristor (GTO), a main snubber circuit and a number of sub snubber circuits are disposed across the anode and cathode of the GTO, and selected ones of the sub snubber circuits are selectively activated by a control circuit in accordance with the magnitude of a main current flowing through the GTO in order to minimize the power loss of the entire snubber circuit. The main snubber circuit includes a capacitor of comparatively small capacity corresponding to a comparatively small and steady main current. The control circuit includes a current detector detecting the main current. For a small steady load, only the main snubber circuit is operated, but at higher loads the control circuit selectively activates an increasing number of the sub snubber circuits. For each sub snubber circuit, the control circuit preferably includes a respective comparator for comparing an output of the current detector to a respective predetermined value and a respective turn-on signal generator for selectively activating the sub snubber circuit in response to an output of the respective comparator.

Snubber circuit for gate turnoff thyristor

A drive circuit for a gate turnoff thyrister (GTO) having a combination of a first switching element and a primary coil of a reactor connected in series between the anode of a power source and the gate electrode of the GTO, a secondary coil of the reactor magnetically coupled with the primary coil thereof and a second switching element connected in series between the gate electrode and cathode of the GTO and adapted to turn 'on' at or above a predetermined voltage. By turning the first switching element on, a forward drive direction primary current of the GTO is generated and flows from the power source and through the primary coil to the gate of the GTO to allow a main circuit current to flow through the GTO. By turning the first switching element off, a reverse drive direction reactor current in the secondary coil of the reactor when the forward drive direction primary current flowing through the primary coil has been interrupted is generated and flows from the cathode of the GTO toward the gate electrode of the GTO through the second switching element to turn the GTO off so that the main circuit current through the GTO is interrupted.

Drive circuit for gate turnoff thyristor

A vapor cooled semiconductor device which comprises an envelope having at least one aperture, at least one semiconductor element enclosed therein, an electrode contacting the semiconductor element and exposed across the aperture of the envelope, an expandable diaphragm disposed through an insulator between the electrode and the wall of the envelope to seal the gap therebetween, spherical spring plates disposed outside the envelope and arranged to support the semiconductor element through the electrode under pressure, and a liquid coolant enclosed in the closed envelope, with space provided therein, whereby the semiconductor element may be cooled by the latent heat of vaporization of the liquid coolant.

Vapor cooled semiconductor device having an improved structure and

A heat transferring or transmitting apparatus characterized by an evaporator containing a semiconductive or heat generating device and being disposed below a condensor unit and connected thereto by two conduits substantially vertically arranged therebetween, such that a coolant gas is passed upwardly through one of the conduits and a coolant liquid is passed downwardly through the other of the conduits, features a resistant element, which may be in the form of a liquid reservoir, disposed in the coolant liquid passage so as to prevent flowing of the coolant gas into and through the coolant liquid passage. The paths of the flowing coolant gas and liquid are thereby kept separate whereby frictional contact therebetween is avoided while circulation is maintained through a phase transition process.

Heat transferring apparatus

A heat transferring apparatus comprising an evaporator and a condensor disposed thereabove, a conduit connecting the evaporator and condensor, and a plurality of fine fabric tubes made of glass fiber or the like disposed in the conduit, the tube walls being permeable to the coolant liquid phase of a coolant being used for cooling an electric or heat generating device in the evaporator, wherein a coolant gas vaporized by the latent heat of gasification in the evaporator is fed to the condensor through the conduit by the increasing pressure caused by the gasification and the coolant gas is then condensed by discharging the latent heat in the condensor, the condensed coolant liquid flowing down into the evaporator under force of gravity and this cycle is repeated to cool the electric or heat generating device. The feedback of the condensed coolant liquid is smoothly performed because of the permeable fabric tube in the conduit allowing the liquid coolant supported above the upflowing gas to permeate thereinto whereby frictional contact between the liquid and gas coolant phases is precluded and the liquid coolant is able to be returned freely through the fabric tubes to the evaporator.

Heat transferring apparatus utilizing phase transition

A stack including a semiconductor element and the associated components is held within a lower portion of a hermetic envelope between its side wall and a closure block movably secured to its opposite side wall to close an opening on the latter and is immersed into a cooling liquid boilable adjacent the operating temperature of the semiconductor element. A pressing plate fixed to the opposite side wall resiliently presses the closure block to apply a compressible contact force to the semiconductor element. The stack may be sandwiched between two closure blocks closing the opposite opening on the bilateral walls of the lower envelope portion and pressed toward each other by two spherical segment of resilient material arranged back-to-back. Alternatively the stack may be carried between the bilateral envelope walls through a resilient spherical segment.

Vapor cooled semiconductor device enclosed in an envelope having a

A capacitor charged with a voltage across anode and cathode of a thyristor after the voltage division and rectification is connected across gate and cathode of the thyristor through a switch while a diode with or without a series reactor is connected across the anode and gate through the same switch. Alternatively a primary winding of an insulating transformer may be connected across the anode and cathode and its secondary winding is operative to charge the capacitor through diodes. The switch is preferably a light switch.

Device for firing thyristor

An ignition apparatus for triggering a plurality of thyristors connected in series and/or in parallel is disclosed. The apparatus includes a high frequency power source, a switch for interrupting the output of the high frequency power source, a pulse generator, a gate transformer for supplying the output of the high frequency power source and the pulse current from the pulse generator to the gate of a thyristor, and a controlling device for controlling the switching time of the switch and the time of pulse-generation by the pulse generator. The switch and the pulse generator are controlled by the controlling device so as to feed a current pulse to the gate transformer from the pulse generator before the output of the high frequency power source is supplied to the gate transformer by actuating the switch. Thus, a gate current having a fast rise time, a desirably controlled time interval and a suitable amplitude is provided supplying a large output capacity for the ignition apparatus for simultaneously triggering the plurality of thyristors connected in series and/or in parallel. This apparatus eliminates the prior art requirement for employment of separate rectangular wave AC generators for each group of thyristors having the same ignition period.

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Amagasaki, Japan

Hiroshi Mitsuoka