JPS5992781A - Commutating circuit for inverter - Google Patents

Abstract

PURPOSE:To suppress the transient current applied to an element and to reduce the number of components by magnetically coupling commutation reactors to be inserted to the arms of thyristors. CONSTITUTION:An inverter has auxiliary thyristors 2, 3, a commutation condenser 4, main thyristors 6, 7 and diodes 8, 9. Commutation reactors 51, 52, 53, 54 are respectively inserted to the arms of the respective thyristors 2, 3, 6, 7. The reactors 51, 53, of positive voltage side are magnetically coupled, and the reactors 52, 54 of negative voltage side are magnetically coupled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a commutation circuit for an impulse commutation type inverter.

An example of a circuit for one phase of a conventional impulse commutation type inverter is shown in FIG. In Figure 1, l is a DC power supply, 2 and 3
is an auxiliary thyristor, 4 is a commutating capacitor, 5 is a commutating reactor, 6 and 7 are main thyristors, and 8 and 9 are diodes.

The operation of the circuit shown in FIG. 1 will be briefly explained.

It is assumed that when current is flowing from the DC power supply l to the load through the main thyristor 6, the commutating capacitor 4 is charged with the polarity shown. When the auxiliary thyristor 2 is ignited, the resonant current from the commutation capacitor 4 and the commutation reactor 5 flows through the route of the commutation capacitor 4 → commutation reactor 5 → main thyristor 6 → auxiliary thyristor 2, and When the current exceeds the load current, the current in the main thyristor 6 becomes 0, which causes the diode 8 to conduct and the main thyristor 6 to extinguish. When the resonant current decreases after reaching its maximum value and becomes equal to the load current, the shortfall in the load current is supplied through the diode 9, so that the current corresponding to the load current flowing through the diode 9 is transferred from the DC power source 1 to the auxiliary sirisk 2 to the converter. The commutation capacitor 4 is It is charged with the opposite polarity as shown. After the current of the diode 9, that is, the load current becomes zero, the main thyristor 7 is turned on, but the electric charge of the commutating capacitor 4, which has been charged with the polarity opposite to that shown in the figure, is used to turn off the main thyristor.

As is clear from the above explanation, charging of the commutation capacitor 4 depends on the load current, so when the thyristor is operated with no load or a light load, the voltage of the commutation capacitor 4 decreases and commutation becomes impossible. .

To prevent this, for example, when the main thyristor 6 is commutating, the main thyristor 〒 is ignited, and the power supply 1 → auxiliary thyristor 2 → commutation capacitor 4 → commutation reactor 5 → main thyristor is connected to the commutation capacitor 4 through the route. Measures are taken to prevent the voltage of the commutating capacitor from decreasing by increasing the amount of charge in the commutating capacitor. However, since diode 8 is conducting during commutation, when the main power switch 1 is turned on, the DC power supply 1 → diode 8
→Because the power is switched on in the main Thyristaff route,
The current of diode 8 becomes O instantly, and the main thyristor
The current changes to the value flowing through the diode 8 immediately before the short circuit. i.e. diode 8 has a very large di/a
Since the arc is extinguished by t, the duty of the diode 8 at the time of arc extinguishing becomes very strict. In order to reduce this, if a limiting reactor is inserted in series with the DC power supply to keep the value of di/dt within a practical range, the inductance of this limiting reactor will be much larger than the wiring inductance, for example 10 Since it has to be multiplied by 20 to 20 times, this limiting reactor becomes extremely large.

The embodiment shown in FIG. 2 has already been proposed as an embodiment that solves the above-mentioned problem. In Fig. 2, the commutation reactor 5 in Fig. 1 is divided into four commutation reactors 51, 52, 53, and 54 and inserted into the arms of each thyristor, so as to have the same effect as the above-mentioned axle. This is what I did. In the same figure 2, 51, 52, 5
All codes other than the commutation reactor 3 and 54 are the first
Same as the figure. The method shown in Figure 2 increases the number of parts and requires sufficient space to eliminate mutual interference due to leakage magnetic flux from the commutation reactor when introduced into the equipment, resulting in a larger equipment. There was a drawback.

The present invention has been made to solve the above-mentioned problems, and aims to provide an inverter commutation circuit that can reduce the number of parts and downsize the device while suppressing di/dt applied to the elements. purpose.

The present invention achieves the above object by magnetically coupling the commutation reactors inserted into each arm of the rhinoceros and risk.

FIG. 3 shows a circuit for one phase of an inverter which is an embodiment of the present invention. In Figure 3, 1 is a DC power supply, 2 and 3 are auxiliary thyristors, 4 is a commutation capacitor, 6 and 7 are main thyristors, 8 and 9 are diodes, and 51, 52, and 54 are inserted into each arm of the thyristor. The commutation reactors 51 and 53 on the positive potential side are magnetically integrated with the illustrated polarity, and the commutation reactors 52 and 54 on the negative potential side are also magnetically coupled with the illustrated polarity. .

The operation of a commutation reactor with broken magnetic coupling will be explained with reference to FIG. In FIG. 3, the inductance of each of the commutation reactors 53 and 54 is Ll, and the commutation reactor 51
Let the inductances of and 52 be L2, and the coupling ratio of commutation reactors 51 and 53 and 52 and 54 be k. Commutation reactors 51 and 53 are involved in extinguishing the main thyristor 6, and if their total inductance is L, then Ll = L2 = Lx. - and k
When = 1, Lx = L/4 and p, and when k = o, LX = L/2. Compared to the case where there is no magnetic coupling, when the coupling rate is 1, the inductance value is set to 50%. I know what I can do.

Next, if a magnetically coupled commutation reactor is used as shown in Fig. 3, the charging voltage of the commutation capacitor will be increased while the commutation current is flowing to extinguish the main thyristor 6. How the a1/at of the diode 8 changes by firing the main thyristor 7 at the same time will be explained with reference to FIG. 4, which is a similar circuit to that shown in FIG.

In FIG. 4, the inductances of the commutation reactors 53 and 54 are respectively Ll, the inductances of the commutation reactors 51 and 52 are respectively L2, and the coupling ratio is the same as described above. E is the voltage of DC power supply 1,
(2) is the voltage of the commutating capacitor 4, but in order to simplify the calculation, (2) is assumed to be constant.

Temporal changes in the current flowing through commutation reactor 51 and commutation reactor 51 at the moment when the main thyristuff is ignited, respectively
2 and k convex ``■=M'', the following equation can be obtained.

P: L2−x2− M・x1+ v +Ll (X
I + X2... Medium... (1) B == L, 1.
XI -M-X2 +L1 (x1+x*) Hit/Song...
Song... (2) From equations (1) and (2), 1-M 2 1.1 - Ll + L2 In other words, diode 8 at the moment the main thyristuff is ignited
d1! /at becomes the above equation (3). Here L1=
L2==L, k=l, F! =1, V=1
．． 35. Since M=L, XI becomes 1/2L from equation (3). Also, L1=L2=L, k
:o, E=1, 'V=1.35, then M=O, so from equation (3), Xl becomes 2.35/3L.

Therefore, when the commutation reactor is the same, when the coupling ratio is 1, the dII/
dt becomes 64%. Conversely, if the coupling ratio is 1, the inductance of the commutation reactor is 64% of that without magnetic coupling.
Even if it is reduced to d1'/at, d1'/at remains the same.

Furthermore, although an air-core commutation reactor is used in this type of inverter, it is necessary to place the two glued handles in close contact with each other in order to create magnetic coupling.

Figures 5 and 6 show an example of a structure in which two rear 7 torques are placed in close contact with each other. It is placed above. In particular, the multi-layer structure shown in FIG. 5 allows two glue axles to be installed in the space occupied by one glue axle, resulting in a significant saving in occupied space, and the number of parts can also be reduced through integration.

FIG. 7 shows the second embodiment of the present invention, and FIG. 8 shows the third embodiment of the present invention.
In this embodiment, the reference numerals given to each part in both FIGS. 7 and 8 are exactly the same as in FIG. 3.

Although the insertion position of the divided commutation reactor inserted on the main side risk side is slightly different from that shown in FIG. 3, its function is the same as that shown in FIG. 3. Furthermore, although the above explanation is for the case where a reverse blocking thyristor is used as the main thyristor,
The same applies when reverse conducting thyristors are used as the main thyristor and diode.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a phase of a conventional impulse commutation iIt type inverter, and FIG. 2 is a circuit diagram of a phase of a conventional impulse commutation type inverter. FIG. 3 is a circuit diagram showing one embodiment of the present invention, and FIG. 4 is an equivalent circuit diagram of FIG. 3. Fifth
The figure shows an example of the structure of a magnetically coupled commutation reactor.
FIG. 6 shows another example of the structure of a commutation reactor for magnetic coupling. FIG. 8 is a circuit diagram showing a second embodiment of the invention, and FIG. 8 is a circuit diagram showing a third embodiment of the invention. 1... DC power supply, 2.3... Commutation reactor, 4.
... Commutation capacitor, 5... Commutation reactor, 6.7
...Main thyristor, 8, 9...Diode, 51
, 52 , 53 . 54... Commutation reactor (split). 7 12 years old 3 figures # 24 years old 5 figures f6 figure 27 figures 3 4 years old 8 figures

Claims (1)

[Claims] 1) The main thyristor is connected in series with a diode connected in anti-parallel to the DC power supply, and the auxiliary thyristor to be connected in series is connected to the power supply in parallel with the main thyristor, and the main thyristor is connected in series. In an impulse commutation type inverter in which the centers of the auxiliary thyristors connected in series with the center of the thyristor are connected to each other via a commutation circuit to form one phase, the commutation reactor is connected to the positive side of the main thyristor and the auxiliary thyristor. A commutation circuit for a positive potential side commutation inverter that is inserted separately into the potential side and negative potential side. 2. A commutation circuit for an inverter according to claim 1, in which commutation occurs between the main thyristor side commutation reactor and the auxiliary thyristor side when a commutation current flows.