Electric power conversion systems – Current conversion – Including automatic or integral protection means
Patent
1984-09-20
1987-01-27
Wong, Peter S.
Electric power conversion systems
Current conversion
Including automatic or integral protection means
363 96, 363136, H02H 7122
Patent
active
046398503
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a power converter device. More particularly, it relates to an inverter device adapted to be used as arm elements for self-extinguishing type switching elements.
A half bridge of a conventional inverter main circuit composed of connected self-extinguishing type switching elements is shown in FIG. 1. In FIG. 1, reference characters P, N respectively denote positive and negative electrodes of a D-C bus, and 1U, 1X denote gate turn-off thyristors (hereinafter simply referred to as GTO) as arm elements, which alternatively receive gate signals to be turned ON and OFF. Reference characters 2U, 2X denote reactors connected in series and inserted between the GIO 1U and the GTO 1X. Reference numerals 3U, 3X denote diodes, the diode 3U being connected in parallel with a series circuit of the GTO 1U and the reactors 2U, 2X, and the diode 3X being connected in parallel with a series circuit of the GTO 1X and the reactors 2U, 2X. Reference characters 4U, 4X respectively denote snubbers of the GTO 1U and GTO 1X. The snubber 4U includes a snubber capacitor 41u, a diode 42u and a resistor 43u, and is connected in parallel with the GTO 1U. The snubber 4X includes of a snubber capacitor 41x, a diode 42x is a resistor 43x and connected in parallel with the GTO 1X. Reference character U denotes an A-C output terminal drawn from the connection point of the reactors 2U, 2X.
Then, operation of the thus-constructed inverter circuit will be described below with reference to FIG. 2.
In FIG. 2, Tu denotes an ON period of the GTO 1U, Tx an ON period of the GTO 1X, Iw a load current flowing through a load (in this example, a delay load). Iu and Ix are, respectively, currents flowing through the GTO 1U and GTO 1X, whereas Iud and Ixd are, respectively, currents flowing through the diodes 3U, 3X. Vuc, Vxc are, respectively, voltages across the snubber capacitors 41u, 41x.
Assume now that the GTO 1U is ON immediately before a time t1 and a load current Iw is supplied to a load, not shown, through the reactor 2U and the A-C output terminal U. When the GTO 1U is turned OFF at a time t1, the current Iu of the GTO 1U flows to the snubber 4U. When the snubber capacitor 41u is charged, the diode 3X is turned ON, and a load current Iw is flowed therethrough. An ON gate signal is appled to the GTO 1X immediately after the time t1, charge stored in the snubber capacitor 41x is discharged through the resistor 43x. When the polarity of the load current Iw is inverted at at a time t2 after the discharge is finished, the diode 3X blocks the load current Iw, and the load current Iw starts flowing through the GTO 1X. Thus, A-C power is produced from the A-C output terminal U.
Thus, since the charge of the snubber capacitor is discharged through the resistor in the conventional one, it has a disadvantage that di/dt duty cycle of the GTO becomes high, and since the charging energy is consumed through the resistor, it has a disadvantage that the conversion efficiency is not preferable.
DISCLOSURE OF THE INVENTION
It is, therefore, an object of the present invention is to provide a power converter device including self-extinguishing-type switching elements (GTO) connected in series to form bridge arm elements for efficiently converting D-C input power into A-C load power. To accomplish this objective, a capacitor discharging circuit having a diode and connected across the diodes of the snubbers, and a power source feedback circuit including a current transformer, are employed to return the current discharged from the snubbers to the input power source. Accordingly, the di/dt duty cycle of the GTO is reduced as compared with the conventional one, and the conversion efficiency can be greatly enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of a half bridge of a conventional inverter;
FIG. 2 is an operating waveform diagram of the inverter;
FIG. 3 is a circuit diagram of an embodiment of the inverter according to the present invention;
FIG. 4 is an operating waveform of each sectio
REFERENCES:
patent: 3349315 (1967-10-01), Studtmann
patent: 4231083 (1980-10-01), Matsuda et al.
patent: 4276588 (1981-06-01), McLyman et al.
patent: 4336587 (1982-06-01), Boettcher, Jr. et al.
"Application Techniques for High Power Gate Turn-Off Thyristors" by R. L. Steigerwald, IEEE IAS '75 Annual, pp. 165-174.
Asaeda Takeaki
Nakamura Toru
Yutani Takashi
Mitsubishi Denki & Kabushiki Kaisha
Wong Peter S.
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