JPH0311193B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter device using a self-extinguishing switching element as an arm element.

FIG. 1 shows a conventional half-bridge inverter main circuit constructed by bridge-connecting self-extinguishing switching elements. In the same figure, P, N
are the positive and negative poles of the DC power supply, and 1U and 1X are gate turn-off thyristors (hereinafter abbreviated as GTO) which are arm elements and are turned on and off alternately.
Receives an on-gate signal to turn off. 2U,
2X is a reactor connected in series.
It is inserted between GTO1U and GTO1X. 3
U, 3X are feedback diodes, 3U is GTO1U, reactor 2U, 2X
In parallel to the series path of, the feedback diode 3X
It is connected in parallel to the series path of GTO1X and reactors 2U and 2X. 4U and 4X are snubbers for GTO1U and GTO1X, respectively, and snubber 4U has a snubber capacitor 41u and a diode 4.
2u, resistor 43u, connected in parallel to GTO1U, snubber 4X is snubber capacitor 41
Consists of X, diode 42X, and resistor 43X
Connected in parallel to GTO1X. U is an AC output terminal and is drawn out from the connection point of reactors 2U and 2X.

Next, the operation of this inverter main circuit will be explained with reference to FIG.

In Figure 2, Tu is the on period of GTO1U,
Tx is the ON period of GTO1X, Iw is the load current flowing to the load (in this example, the slow phase load), Iu and Ix are the currents flowing to GTO1U and GTO1X, respectively, Iud,
Ixd is the current flowing through the feedback diodes 3U and 3X, respectively, and Vuc and Vxc are the voltages of the snubber capacitors 41U and 41X, respectively.

Now, it is assumed that the GTO 1U is turned on immediately before time t1, and a load current Iw is supplied to a load (not shown) through the reactor 2U and the AC output terminal U. At time t1, GTO1U
When turned off, the current Iu of the GTO 1U flows to the snubber 4U, and when the snubber capacitor 41u is charged, the feedback diode 3X is turned on, and the load current Iw flows through it. Time t1 for GTO1X
Immediately after, an on-gate signal is applied, and the charge stored in the snubber capacitor 41x is transferred to the resistor 43x.
After the discharge ends, at time t2
When the polarity of the load current 1w is reversed, the feedback diode 3X begins to block the load current 1w, and the load current 1w begins to flow through the GTO 1X. In this way, AC power is taken out from the AC output terminal U.

In this way, in the conventional type, the charge of the snubber capacitor is discharged through the resistor, so the GTO
It has the disadvantage that the di/dt debt becomes high, and the conversion efficiency is not good because the charging energy is consumed by the snubber resistance.

This invention was made in order to eliminate the above-mentioned conventional drawbacks, and it connects a snubber consisting of a capacitor and a diode in parallel to the positive and negative arm elements, and connects the capacitor side of the diodes of both snubbers via a diode circuit. By forming a capacitor discharge circuit that passes through the reactor between arm elements, and taking out the discharge current flowing through the diode circuit via a current transformer and converting it to the DC power supply side, self-extinguishing is achieved compared to conventional methods. It is an object of the present invention to provide an inverter device that can reduce the di/dt liability of type switching elements, greatly increase the conversion efficiency, and does not generate overvoltage when resetting a current transformer.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 5U is a snubber, which is composed of a snubber capacitor 51u and a diode 52u connected in series with the snubber capacitor 51u, and is connected in parallel to the GTO 1U. 5X is a snubber, which is composed of a snubber capacitor 51x and a diode 52x connected in series with the snubber capacitor 51x, and is connected in parallel to GTO 1X. Diode 52 of snubber 5U
diode 52x on the anode side of u and snubber 5x
is connected to the cathode side of the circuit through a diode circuit 6. This diode circuit 6 is inserted with its cathode side facing the anode side of the diode 52u. 7 is a current transformer inserted into the diode circuit 6, both ends 7a and 7b of the secondary winding are connected to the positive terminal P of the DC power supply via diodes 8a and 8b, respectively, and diodes 8c and 8d.
It is connected to the negative pole N of the DC power supply via. The diodes 8a, 8b, 8c, and 8d constitute a bridge circuit. Since the other configurations are the same as those in FIG. 1, the same reference numerals are given.

Next, the operation of this main circuit will be explained with reference to FIG. In FIG. 4, ID indicates the current flowing through the diode circuit 6 and current transformer 7.

At time t1, the GTO that had been turned on until now
When 1U is turned off, the current flowing through GTO 1U is transferred to snubber 5U, and snubber capacitor 51u is charged. At this time, the charge of the snubber capacitor 51x of the snubber 5X is transferred to the diode circuit 6-
Current transformer 7 - diode 52u - reactor 2U -
It is discharged through the AC output terminal U to a load (not shown). Immediately after time t1, when GTO 1X is turned on, the charge of snubber capacitor 51x is transferred to diode circuit 6 - current transformer 7 - diode 52u -
It is discharged through reactor 2U-reactor 2X-GTO1X. When the discharge current of the snubber capacitor 51x flows to the current transformer 7, its secondary output is returned to the DC power supply via the diodes 8a and 8d. In this case, the diode 8b,
8c turns on and serves to clamp the voltage between terminals 7a and 7b to the voltage between the positive and negative electrodes of the DC power supply,
Speed up the reset of current transformer 7. When the charging of the snubber capacitor 51u is completed, the load current Iw flows through the feedback diode 3X, the reactor 2U, and the output terminal U, but does not flow to the GTO1X, and when the polarity is reversed at time t2, the feedback diode 3X is turned off. , flows through reactor 2X-GTO1X.

That is, when one of the GTO 1U and GTO 1X is turned on, a discharge path including the series reactors 2U and 2X is closed, and the discharge current of the snubber capacitor flows through the discharge path, so that the di/dt obligation of the GTO is reduced. Also, when the other GTO turns off, the charge in the snubber capacitor flows to the load through the diode circuit 6, the snubber diode of the other GTO, and one of the reactors.
The turn-on periods of U and GTO1X are separated,
If there is a period when both are off at the same time, the power conversion efficiency increases, and furthermore, when the snubber capacitor is discharged, the discharge current flows from the secondary side of the current transformer 7 to the DC power supply side through the diodes 8a and 8d. Since the power is returned, power conversion efficiency can be further improved.

FIG. 5 shows another embodiment of the invention, in which the feedback diodes 3U and 3X are connected to the GTO
Although it differs from the above embodiment in that it is connected in antiparallel to 1U and GTO 1X, as shown in FIG.
When the GTO 1U is turned off, the snubber capacitor 51u is charged, and the charge of the snubber capacitor 51x flows to a load (not shown) through the diode circuit 6, current transformer 7, diode 52u, and reactor 2U. When this charging/discharging is completed, feedback diode 3X - diode 52x - diode circuit 6 - converter 7 - diode 52u - reactor 2
Load current Iw flows through U. Also, GTO1X
When turned on, the charge in the snubber capacitor 51x is discharged through the reactors 2U and 2X.

The charging energy of the snubber capacitor taken out via the current transformer 7 may be returned to another DC power source.

Although each of the above embodiments has been explained using a half bridge, it is clear that the same effect can be obtained even if a large number of half bridges are connected in parallel to form a multiphase inverter.

Further, the self-extinguishing switching element may be any switching element having a self-extinguishing ability, such as a transistor.

As described above, according to the present invention, by removing the resistance of the snubbers of the positive and negative arm elements and connecting the capacitor sides of the diodes of both snubbers through a diode circuit, the electric charge of the capacitor is passed through the reactor between the positive and negative arm elements. Since it is configured to discharge, the di/dt liability of the self-extinguishing switching element can be reduced compared to the conventional one.Not only does the snubber have no resistance, but the current flowing through the diode circuit can be transferred to a current transformer. Since the current transformer is converted to a DC power source through a diode bridge circuit, the power conversion efficiency can be greatly increased compared to conventional methods. Since the current transformer is connected, there is an advantage that there is no need to provide an overvoltage suppressing element in the current transformer.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional half-bridge inverter, FIG. 2 is an operating waveform diagram of each part of the above inverter, FIG. 3 is a circuit diagram of an embodiment of the inverter according to the present invention, and FIG. 4 is a circuit diagram of each part of the above embodiment. FIG. 5 is a circuit diagram of another embodiment of the present invention.
FIG. 6 is a waveform diagram of each part of the embodiment shown in FIG. In the figure, 1U, 1X... self-extinguishing switching element, 2U, 2X... reactor, 5U,
5X...Snubber, 6...Diode circuit, 7...
Current transformer, 7a, 7b... Current transformer terminals, 8a, 8
b, 8c, 8d...diode, 51u, 51x
...Snubber capacitor, 52u, 52x...diode. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In an inverter in which a self-extinguishing switching element is used as an arm element and a reactor is provided in each positive and negative arm, a snubber consisting of a snubber capacitor and a diode connected in series with the snubber is connected in parallel to each of the positive and negative arm elements, and The snubber capacitor sides of the diodes of both snubbers are connected to both diodes through a forward diode circuit, and a current transformer is inserted into the diode circuit, and both ends of the secondary winding of the current transformer are connected to the diodes. An inverter device connected to a DC power supply via a bridge circuit.