JPH0315227A - Snubber circuit - Google Patents

Abstract

PURPOSE:To restrain a transient overvoltage by a method wherein a common first summarized snubber circuit, provided between the positive pole arm and the negative pole arm of a power converting device, is provided with a second summarized snubber circuit in parallel to the first summarized snubber circuit. CONSTITUTION:An AC input, inputted from a terminal 10, is converted into a DC by GTO thyristors 4, 5, and free-wheel diodes 5, 7 to output it from a positive pole 8 and a negative pole 9. A first common snubber circuit 1, formed of capacitors 101, 102, diodes 103, 104 and a resistor 5, is connected to the positive pole 8 and the negative pole 9. A second common snubber circuit 2 is formed of capacitors 201, 202, diodes 203, 204 and the resistor 5 and is connected between the positive pole 8 and the negative pole 9 in parallel to the first common snubber circuit 1 to restrain the equivalent inductance of the snubber circuit upon package wiring. According to this method, a transient overvoltage may be restrained and the GTO thyristor may be protected effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to self-extinguishing switching elements (for example, GT
The present invention relates to a mounting technology in a snubber circuit of a power converter using a power converter (O thyristor), and particularly relates to a power converter suitable for driving a large-capacity AC motor.

[Conventional technology]

Conventionally, regarding snubber circuits for power converters, IE, I.21.S., Conference Record (1987), pp. 577 to 583 (IE
EE, IAS, Conf. Rec. (1 9 8 7
) pp 577-583).

This snubber circuit is connected to the positive arm GT as shown in FIG.
A collective snubber circuit 1 common to the O-thyristor 4 and the negative arm GT-thyristor 5 is provided.

[Problem to be solved by the invention]

The above conventional technology does not take into account the fact that the wiring length increases due to the larger dimensions of the collective snubber circuit, which is common to both the positive and negative arms, and the wiring inductance during switching causes the GTO thyristor to There was a problem that overvoltage was applied. For example, the 8th
In the conventional circuit shown in figure (a), GT○thyristor 4
Voltage vo and current i of GT○4 when turns off
The digit will be as shown in (b). At the point when the current drops, the voltage jumps up in approximately proportion to the wiring inductance component of the snubber circuit. If this rising voltage vosp becomes excessive, the operating point of the GTO will be outside the safe operating range, leading to destruction. In order to reduce Vosp, it is necessary to reduce the wiring inductance as much as possible. An object of the present invention is to provide a snubber circuit that can equivalently reduce the wiring inductance and that can utilize the energy load or recover power during switching, which is a feature of the conventional collective snubber circuit.

[Means for Solving the Problems] The above object is achieved by connecting a second collective snubber circuit of small capacity in parallel to the collective snubber circuit.

[Effect]

The capacitance of each capacitor constituting the second collective snubber circuit is made smaller than the capacitance of each corresponding capacitor in the first collective snubber circuit.

In this way, the size of the capacitor of the second collective snubber circuit can be reduced, so that the inductance due to the wiring and the equivalent inductance inside the capacitor can be reduced.

Due to this. It is possible to suppress the jump voltage that occurs during switching to a low level.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows the configuration of one phase of the power converter.

The positive arm consists of a GT○ thyristor 4 and a freewheeling diode 6, and the negative arm consists of a GTO thyristor 5 and a freewheeling diode 7. capacitor 10
1,102. A first collective snubber circuit 1 composed of diodes 103, 104 and a resistor 105 is connected in parallel to the positive and negative polar arms. 10 is an AC side terminal, and 8 and 9 are DC side terminals. A second snubber circuit 2 is further provided in parallel with the first snubber circuit 1. The circuit configuration consists of capacitors 201, 202, diodes 203, 204, and resistor 205, similar to the first snubber circuit 1. The capacitance of capacitors 101, 102, 201, 202 that constitute each snubber circuit is C1011 C1021 Cxo1, C2
02, Czot≦CLOL, Czoz≦C
The following relationship is established: toz ゜−(L). Generally, in capacitors, if the voltage ratings are the same, a capacitor with a smaller capacitance is smaller in size than a capacitor with a larger capacitance. Therefore,
The wiring length at the time of mounting in the second batch snubber circuit 2 is
Since the internal equivalent inductance of the capacitor is also smaller, the inductance of the path including the capacitor 201, diode 203, and capacitor 202 and the path including the capacitor 202 and diode 204 can be made shorter than that of the first collective snubber circuit. Can be made smaller. FIG. 2 shows an equivalent circuit that takes these inductances into account. Reactor 206, 207, 208,
106, 107, etc., as L 208 ,
L2Q71 Lzos, L5on, L107, etc. When the capacitor capacity is in the relationship of formula (1), Lzoe<Ltoa+ L207<CL107, L
zoa<Llon...(2) It is quite possible to establish the relationship. For example, if the former value is about ↓/5 to 1710 of the latter value, then (2
) satisfies the formula. For example, as shown in Figure 3(a),
Consider the case where a load current i is flowing through the TO thyristor 4 and an off-gate signal is input. The diode 103 of the first snubber circuit and the diode 203 of the second snubber circuit become conductive and can be expressed by the equivalent path shown in (b). Here, .

The following holds true from the relationship between equations (l) and (2). Next, the impedances Z1 and Z2 of each snubber circuit are as follows from (b), and from the relationship of equation (4), f=<fz. For each snubber circuit, the impedance of the capacitor becomes dominant at frequencies lower than the resonant frequency, and the impedance of the actuator becomes dominant at frequencies higher than the resonant frequency. Moreover, (4)
From the relationship in the equation, if Zzl is set, then from the relationship in equation (4), if IZll, lZzl is illustrated as a function of the angular frequency ω (=2πf), it becomes as shown in Figure 3 (
C). Here, fx and fx are the resonant frequencies of each snubber circuit, and are expressed as follows (8). Next, the parallel composite impedance 2 of the first snubber circuit and the second snubber circuit is calculated as shown in the following equation.

Zx+Zz l2111Z21 From equations (8) and (9), the following approximation can be made: (10). Regarding impedance, considering that the capacitor is dominant in the low frequency region and the beam actor is dominant in the high frequency region, IZ1 of equation (9)
becomes a function as shown by the broken line in FIG. 3(c). That is, in the frequency range lower than fx, the capacitor Cxzx
is dominant in the frequency region higher than f2, the beam actor L
220 becomes dominant, and over a wide frequency range, the impedance I in the case of only the first snubber circuit l
It has a lower impedance than Z41. The lower +21 is, the lower the voltage vo:i XZ generated by the load current iL flowing into the snubber circuit from the current source 11 immediately after the GTO thyristor 4 is turned off. Therefore, the jump voltage V asp shown in FIG. 8(b) in the conventional example can be suppressed to a low level.

When the negative arm GTO thyristor 5 turns off, the path of the reactor 107, capacitor 102, diode 104, and reactor 108 of the first snubber circuit 1 in FIG. , capacitor 202, diode 204,
It is only necessary to consider the route of the reactor 208, and the same effect as in the case of the positive electrode arm can be obtained.

FIG. 4 is a circuit diagram showing the second embodiment. This embodiment uses the resistor 205 and the resistor 10 in FIG. 1 in the first embodiment.
5 is used in common, and the constituent elements of the second snubber circuit are connected in parallel to each constituent element of the first snubber circuit. In terms of suppressing transient voltage spikes, the current path can be considered in the same manner as in FIG. 3, and exactly the same effect can be obtained. In this embodiment, since only one resistor is needed, the device can be made smaller. Furthermore, since the structural elements of the first snubber circuit and the second snubber circuit are connected in parallel, there is an effect that the capacitor capacity and diode allowable current in a steady state can be increased.

FIG. 5 is a circuit diagram showing a third embodiment. In this embodiment, the capacitor 202 shown in FIG. 4 in the second embodiment is also separated into the negative pole arm, and the capacitor 202 and the capacitor 20
This is an example in which 5 is provided.

In this embodiment, a capacitor 201, a diode 203,
Since the wiring inductance of the path of the capacitor 202 and the path of the capacitor, capacitor 205, and diode 204 can be further shortened, there is an effect that the surge voltage can be reduced accordingly. Also, the capacitor 102
Since capacitor 202 and capacitor 205 are connected in parallel, there is also the effect that the equivalent capacitor capacity can be further increased.

FIG. 6 is a circuit diagram showing a fourth embodiment. This embodiment is an example in which the diodes 103 and 104 of the first collective snubber circuit l are omitted from FIG. 4 showing the second embodiment, and only the diodes 203 and 204 are used. This embodiment has the effect that circuit implementation is easier because the number of diodes is reduced.

FIG. 7 is a circuit diagram showing the fifth embodiment. In this embodiment, the diode of the first collective snubber circuit in FIG. 5 showing the third embodiment is omitted, and the same effect as that of the fourth embodiment is obtained.

〔Effect of the invention〕

According to the present invention, since it is possible to reduce the equivalent inductance when mounting and wiring the collective snubber, there is an effect that the transient jump voltage can be suppressed to a low level. Moreover, the present invention... It is effective in protecting GTO thyristors, and when applied to power conversion devices such as inverters and converters, it is effective in protecting devices.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a detailed circuit diagram of Fig. 1, Fig. 3 is an explanatory diagram of the operation of Figs. 1 and 2, and Figs. 4 to 7 are Circuit diagrams of the second to fifth embodiments, and FIG. 8 are circuit diagrams showing a conventional example. l...First batch snubber circuit, V DSP...GT○
Voltage that jumps between the thyristor annotated cathode, 2...
・Second batch snubber circuit, 106 to 108, 120, 2
0 6 - 2 0 8 , 2 2 0 ... Wiring reactor, L108 ~ Ltoat Lt2o+
I, zoo~Lzoa+ Lzzo - wiring inductance, 2...zl, parallel combination of Z2 or impedance, z1... impedance of the first collective snubber circuit. Z2: Impedance of the second collective snubber circuit. Fig. 1 + Fig. 2 2θ3 g θg Fig. 4 Fig. 3 Fig. 5 Section + Fig. 6 Fig. 7

Claims (1)

[Scope of Claims] 1. A power conversion device having a collective snubber circuit provided in common to a positive pole arm and a negative pole arm, characterized in that a second collective snubber circuit is provided in parallel to the snubber circuit. . 2. The snubber circuit according to claim 1, wherein each element constituting the second collective snubber circuit is connected in parallel to each corresponding element in the first collective snubber circuit. 3. The snubber circuit according to claim 1 or 2, characterized in that the capacitance of each capacitor constituting the second collective snubber circuit is smaller than the capacitance of the corresponding capacitor in the first collective snubber circuit. snubber circuit. 4. In the snubber circuit according to claim 2, 3 or 4, the wiring length of each element constituting the second collective snubber circuit is
A snubber circuit characterized in that it is shorter than that of the collective snubber circuit.