JPH04275067A - Snubber circuit for self-arc extinguishing type switching element - Google Patents

Abstract

PURPOSE:To eliminate a snubber resistor by once transferring charge stored in a snubber capacitor to a capacitor, and returning it to a power source. CONSTITUTION:When a thyristor 41 is turned ON in a state that a load current flows through a diode 53, a current flows in a circuit of the thyristor 41, a capacitor 73 and a diode 63 to charge the capacitor 73. Simultaneously, the charge of a capacitor 71 is discharged in a circuit of the capacitor 71, a capacitor 111 and the capacitor 71, and the charge of the capacitor 71 charged at the time of turning OFF the thyristor 41 is transferred to the capacitor 111. When the load current flows through the thyristor 41 to complete a commutation, the charge transferred to the capacitor 111 is returned to a power supply in circuit of the capacitor 111, a Zener diode 91, a reactor 101, a DC power supply 1, a reactor 103, a Zener diode 93 and the capacitor 111.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to self-extinguishing thyristors (hereinafter simply referred to as thyristors) such as gate turn-off thyristors and static induction thyristors, transistors, and IGs.
The present invention relates to a bridge inverter using a self-extinguishing switching element such as a BT, and particularly to a snubber circuit using a self-extinguishing switching element that returns power from the snubber circuit to the power source to reduce circuit loss.

0002

2. Description of the Related Art FIG. 3 shows an example of a commonly used thyristor snubber circuit, in which 1 is a DC power supply, 2 is a reactor included in the power supply line, and 3 is a thyristor 41, 42, 43.
, 44 are diodes for energy feedback. Here, the thyristors 41 and 44 and the thyristors 42 and 43 are repeatedly turned on and off at the same time, thereby performing an operation of supplying AC power to the load 3.

In FIG. 3, 61, 62, 63, 64 are diodes, 71, 72, 73, 74 are capacitors, and 8
1, 82, 83, and 84 are resistors. diode 61,
62, 63, 64 and capacitors 71, 72, 73, 74
and resistors 81, 82, 83, 84 are thyristors 41, 42
, 43, and 44, which constitute a snubber circuit connected to protect them, respectively.

FIG. 4 shows a case where the thyristor 41 transitions from an on state to an off state at time T1. When the thyristor 41 turns off, the current It flowing through the thyristor 41 flows through the diode 61 and the capacitor 71 (current Isp), reducing the switching loss of the thyristor 41 and causing a sudden increase in the voltage applied to the thyristor 41. and suppress overvoltage. When the thyristor 41 turns on at time T2, the capacitor 7 that was charged at the time of turning off
A charge Vsp of 1 is discharged through the resistor 81 and the thyristor 41, and the energy is consumed by the snubber resistor and converted into heat.

[0005]

In this type of conventional circuit, the charge in the snubber capacitor is repeatedly charged and discharged depending on whether the thyristor is turned on or off. At this time, the loss P (W) generated in the snubber resistor is calculated using the capacitance of the snubber capacitor as C,
Assuming that the charging voltage is V (V) and the operating frequency is F (Hz), it can be approximately expressed by the following equation. P=(1/2)CV2 F・・・・・・・・・・・・
・・・・・・・・・■

The loss caused by the snubber resistance increases rapidly, especially when the voltage and frequency are large, or when the inverter becomes large and has a large inductance, and the capacitance C must be increased, and the amount of heat generated increases. It becomes large and causes problems in heat treatment.

The present invention is made by eliminating the above-mentioned disadvantages, and an object of the present invention is to provide a snubber circuit of a self-extinguishing switching element that can effectively reduce power loss in the snubber circuit. .

[0008]

[Means for Solving the Problems] The circuit configuration according to the present invention is as follows. A first snubber circuit has a first snubber diode connected to the anode side of a first self-extinguishing switching element on the positive side, and a first snubber capacitor connected to the cathode side, and a second snubber circuit on the negative side. a second snubber circuit in which a second snubber capacitor is connected to the anode side of the self-arc-extinguishing switching element and a second snubber diode is connected to the cathode side;

[0009] A capacitor is provided between the connection point between the first snubber diode and the first snubber capacitor, and the connection point between the second snubber capacitor and the second snubber diode, and the positive terminal of this capacitor is connected to the power supply line. A series connection body consisting of a Zener diode and a reactor is provided between the positive electrode and between the negative electrode of the capacitor and the negative electrode of the power supply line.

0010

[Operation] In this circuit configuration, the charge charged in the snubber capacitor is transferred to the capacitor once, and the voltage of the capacitor is greater than or equal to the sum of the power supply voltage and twice the Zener voltage between the capacitor and the positive or negative pole of the power supply line. When this happens, it can be returned to the power source. Furthermore, the snubber resistor connected in parallel to the snubber diode can be removed.

[0011]

[Embodiment] Fig. 1 shows the main part configuration of an embodiment of the present invention, in which 91, 92, 93, 94 are Zener diodes;
101 , 102 , 103 , 104 are reactors, and 111 , 112 are capacitors. In the figure, Figure 3
Parts with the same reference numerals indicate parts having the same function.

That is, in the snubber circuit component of thyristor 41 and thyristor 43, thyristor 41
A first snubber circuit is configured in which a diode 61 is connected to the anode side and a capacitor 71 is connected to the cathode side. Further, a second snubber circuit is configured in which a capacitor 73 is connected to the anode side of the thyristor 43 and a diode 63 is connected to the cathode side.

Furthermore, a diode 61 and a capacitor 71
A capacitor 111 is provided between the connection point of the capacitor 73 and the diode 63. Then, the charges charged in the capacitors 71, 72, 73, and 74 can be temporarily transferred to the capacitors 111 and 112.

Furthermore, a series connection of a Zener diode 91 and a reactor 101 is connected between the positive terminal of the capacitor 71 and the positive terminal of the power supply line.
A series connection body of a Zener diode 93 and a reactor 103 is connected between the negative electrode of the power supply line No. 3 and the negative electrode of the power supply line. When the voltage of the capacitor 111 exceeds the sum of the power supply voltage and twice the Zener voltage, the charge transferred to the capacitor can be returned to the power supply via the Zener diode and reactor.

As described above, in this embodiment, the capacitor 111
, 112 and Zener diodes 91, 92, 93, 9
4 and reactors 101, 102, 103, 1
By adding the series circuit consisting of 04, the resistors 81, 82, 83, and 84 shown in FIG. 3 are removed, and the snubber power can be skillfully processed without loss. This operation will be further explained in detail with reference to FIG.

FIG. 2 is an explanatory diagram of the operation of FIG. 1 similar to FIG. 4. Now, in a state where the load current is flowing through the thyristor 41 [at this time, the voltage of the capacitors 71 and 73 is V
sp, Vsn are (Vsp=2Vz), (Vsn=V
)], if the thyristor 41 is turned off at time T1, the current that has been flowing through the thyristor 41 will flow through the diode 61 and the capacitor 71, preventing a sudden rise in the voltage applied to the thyristor 41. , and also suppresses overvoltage.

At this time, the voltage Vc of the capacitor 111
can be assumed to be a constant voltage (Vc=V+2Vz), and the capacitor 71 is charged with (Vsp=2Vz) as an initial value. At the same time, (Vsp+Vsn>Vc), the charge in the capacitor 73 is discharged along the path of capacitor 73→capacitor 71→capacitor 111→capacitor 73, and the charge in capacitor 73 is transferred to capacitor 111. Here, the charge of the capacitor 73 is also discharged along the path of capacitor 73 → thyristor 43 → reactor 103 → Zener diode 93 → capacitor 73, but because of the reactor 103, this discharge is much slower than the former and can be ignored.

When (Vsp=V) and (Vsn=2Vz), the load current flows through the diode 53 and commutation is completed. (The charges on the capacitors 71 and 73 at this time become the initial value for the next commutation.)

Next, when the thyristor 41 is turned on at time T2 from the state where the load current is flowing through the diode 53, the current flows through the path of the thyristor 41 → capacitor 73 → diode 63, and the current flows through the capacitor 73.
is charged.

At the same time, since (Vsp+Vsn>Vc), the charge on the capacitor 71 is discharged along the path of capacitor 71 → capacitor 111 → capacitor 73 → capacitor 71, and the charge on capacitor 71 charged when thyristor 41 is turned off is transferred to capacitor 111. Transition.

On the other hand, here too, the charge of the capacitor 71 is
Discharge also occurs in the path of capacitor 71 → Zener diode 91 → reactor 101 → thyristor 41 → capacitor 71, but because of the reactor 101, this discharge is much slower than the former and can be ignored.

(Vsn=V) and (Vsp=2Vz), the load current flows through the thyristor 41, and commutation is completed. (The voltages of the capacitors 71 and 73 at this time become the initial values for the next commutation.) The charge transferred to the capacitor 111 is always
It is returned to the power supply through the route of capacitor 111 → Zener diode 91 → reactor 101 → DC power supply 1 → reactor 103 → Zener diode 93 → capacitor 111. This operation is repeated thereafter.

Here, Zener diodes 91, 92,
As can be seen from the above-described operation, 93 and 94 are necessary to always return the snubber power from the capacitors 111 and 112 to the direction of the DC power supply 1. If this Zener diode is not provided, the snubber power will circulate, for example, from the snubber diode 61 to the reactor 101, or between the capacitor 111 and the DC power supply 1.

The voltage Vc of the capacitor 111 is (V+
2Vz), and the values of capacitors 111 and 112 are Co
, Cs is the value of the capacitors 71, 72, 73, and 74. Since Co is extremely large compared to Cs, it is considered to be a constant voltage. In addition, reactors 101 and 102
, 103, 104, the average value Io of the current flowing through them is:
There is a relationship as shown below. Io ・(V+2Vz)=(1/2)Cs ・V2
・F・2・・・・・・・・・■

[V=600 (V)], [VZ =5(
V)], [Cs = 0.022 (μF)], [F = 1
0 (kHz)], then [Io = 0.13 (A
)]. Here, if (Vz > 0), then (V
c > V) and the energy of the capacitors 111 and 112 can be returned to the DC power supply 1, so the Zener diodes 91, 92, 93, and 94 may be diodes or pure resistors.

[0026] In this way, the snubber power [P=(1/2)・CV2F] conventionally consumed by the snubber resistor is returned to the power supply without loss, so even if the circuit voltage and frequency increase However, it does not increase snubber losses and impair circuit performance.

[0027]

As explained above, according to the present invention, it is possible to provide a device with a simple configuration that returns snubber power to a power source with almost no loss. The above effect is extremely large.

[0028]

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a main part configuration of an embodiment of the present invention.

FIG. 2 is a waveform diagram showing waveforms of various parts in FIG. 1;

FIG. 3 is a circuit diagram showing a conventional example.

FIG. 4 is a waveform diagram showing waveforms of various parts in FIG. 3;

[0029]

[Explanation of symbols]

1 DC power supply 41 Thyristor 43 Thyristor 61 Diode 63 Diode 71 Capacitor 73 Capacitor 91 Zener diode 92 Zener diode 101 Reactor 103 Reactor 111 Capacitor 112 Capacitor

Claims (1)

[Claims] Claim 1: An inverter comprising a self-extinguishing switching element, wherein a first snubber diode and a first snubber capacitor are connected in series in parallel to the first self-extinguishing switching element on the positive side. and a second snubber circuit in which a second snubber diode and a second snubber capacitor are connected in series in parallel to the second self-extinguishing switching element on the negative side, connecting a capacitor between a first connection point between the snubber diode and the first snubber capacitor and a second connection point between the second snubber diode and the second snubber capacitor;
A first series circuit including a first reactor and a first Zener diode is connected between the anode side of the first self-extinguishing switching element and the first connection point, and A snubber for a self-arc-extinguishing switching element, characterized in that a series circuit consisting of a second reactor and a second Zener diode is connected between the cathode side of the self-arc-extinguishing switching element and the second connection point. circuit.