JPS61293179A - Protecting device for gto thyristor inverter - Google Patents

Abstract

PURPOSE:To reduce the size and to enhance the reliability of a protecting device of a GTO thyristor inverter by providing means for monitoring a voltage between a gate and a cathode of a GTO thyristor according to the conduction or nonconduction of the thyristor. CONSTITUTION:Snubber diodes SD1, SD2, snubber capacitors C11, C12 and snubber resistors R1, R2 are connected with an inverter main circuit having GTO thyristors G11, G12 and feedback diodes D11, D12 for the purpose of controlling dV/dt of a voltage between an anode and a cathode when the GTOs are turned OFF. High voltage side circuits 2A, 2B are provided corresponding to the GTO thyristors G11, G12. Voltage detectors 22a... are connected between the gates and the cathodes of the thyristors G11, G12, thereby detecting the conduction or nonconduction of the thyristors G11, G12.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an inverter using a so-called gate turn-off thyristor (hereinafter also simply referred to as GTO) whose conduction/non-conduction state can be controlled by a gate signal. Regarding protective devices.

[Prior Art No. H Fenglu] Regarding an inverter protection device that requires one person, the applicant has proposed the following (see Japanese Patent Application No. 59-40515).

FIG. 6 is a block diagram showing the proposed inverter protection device, FIG. 7A is a time chart for explaining the arm short circuit accident avoidance function in the block diagram of FIG. It is a time chart for explaining the protective operation when the arm short-circuit accident occurs in the figure.

In Fig. 6, 1 is the low voltage side logic operation circuit, 2A, 2
B is a high voltage side circuit, and 5 is a control circuit. The inverter main circuit consisting of the GTO thyristor Gll, 12 and the feedback diode Dll, 12 has a dV/dt (
Snubber diode S is used to suppress the off-voltage rise rate).
DI, Sn2) A snubber capacitor C1l, 12 and a snubber resistor R1, 2 are connected. High voltage side circuit 2A
.

2B are provided corresponding to the GTO thyristors Gll and 12, respectively, and are composed of a gate drive circuit, a voltage detector, a comparison circuit, and the like. For example, the gate drive circuit 21a in the two high-voltage side circuits supplies a gate current to the GTO thyristor Gll, and the voltage detector 22a detects the terminal voltage of the capacitor C1l corresponding to the voltage between A- of the GTO thyristor 011, Also, the comparator M23a converts the output of this detector 22a into the ON/OFF state of the GTO thyristor Gll.
Convert to a logic signal corresponding to the F state. Although the details of the high-voltage side circuit 2B are omitted, it is constructed in the same way. The low-voltage side logic operation circuit 1 has the comparison circuit outputs C1, 2) from the high-voltage side circuits 2A, 2B, and the control circuit 5.
Ignition command pio, p20 and OR gate OR3 from
6 by inputting the full firing signal S etc. at the time of arm short circuit via
．． Gate drive signal Q1.2 and arm short circuit detection signal O
It outputs U, or game) 011, 1, 2) anime game) ANI, 2 and Noah game) NO11 (
, etc. In addition, 3 and 4 in the 6th V
is the short circuit thyristor and its ignition unit.

Here, the arm short circuit avoidance operation will be described with reference to FIG. 7A. In addition, the signals AI, 2) C1,
2) PIo, 20. Ql, 2 and S respectively correspond to those in FIG. 6, and A1e2 is the capacitor C1l.
, 12, which is proportional to the die pressure between A- and GTO.

Now, at time tf, G'l'0 thyristor G12
If the turn-off becomes impossible, that is, A2 in the same figure
As shown, it should normally be off as shown by the dotted line (signals A1 and A2 are at high level when the GTO is off).
However, if this remains on, the corresponding comparator output C2 will also be at a low level (signal C
1 and 2 are at low level when the GTO is on. ) remains the same. Therefore, in FIG. 6, even if the control circuit 5 issues the firing command P10 to the GTO thyristor GI IK, the comparator circuit output C2 from the high voltage side circuit 2B does not open the ant gate AN1, so this is blocked. The gate drive signal Q1 for the thyristor Gll also remains at a low level, and an arm short-circuit accident is avoided. Note that this relationship is the same even when the firing thyristor Gll fails to turn off, and in this case, the firing command P20 is
is blocked by the comparator circuit output C1 from the two high-voltage side circuits.

Next, with reference to FIG. 7B, a protective operation when an arm short circuit occurs will be described. Note that the various signals in this case also correspond to those in FIG. 6, as in the case of FIG. 7A.

Now, at time ts when the thyristor Gll is firing as shown by A1 in the figure, due to erroneous firing or failure of the thyristor G12, the capacitor voltage A2 is discharged as shown in the diagram, and the voltage level changes to the operation of the comparator. It is assumed that the level has been reached. As a result, the comparison circuit output C2 becomes low level after a predetermined time from time ts as shown in the figure, but at this time, the comparison circuit output CI of the two high voltage side circuits is also low level as shown in the figure. These low level signals CI.

2 is applied to the NOR gate NOR in FIG. 6, and a high level signal OU is output from its output.

This signal OU is passed through the OR gate OR3 to the total firing signal S.
Then, each thyristor Gll, 12 is fired via the OR gate ORI, 2, and the short-circuit thyristor 3 is fired via the firing unit 4, thereby dividing the short-circuit current and performing the entire protection operation.

It goes without saying that the above relationship holds true even if the thyristor Gll side is erroneously fired for some reason while the thyristor G12 is firing.

FIG. 8 is a block diagram showing another embodiment of the proposed inverter protection device. As is clear from the same figure, this example is different from that shown in FIG. 6 in that there is no short-circuit thyristor and that the low-voltage side circuit 11 is provided with ant gates AN3, AN4 instead of the OR gate. It's full of ingredients. Therefore, in the event of a short circuit accident, AND gate AN3,
The GTO is turned off by the gate drive signals Q1 and Q2 via the circuit 4, thereby cutting off the short circuit current and thereby preventing the short circuit from occurring. In this case, since a large short-circuit current does not flow, the fuse is not blown and therefore no conversion is required.

[Problem that the invention seeks to solve]

However, according to what is shown in FIG. 6, the high voltage side circuit 2A,
Since the voltage detector 22a used in the GTO thyristor G11 directly detects the terminal voltage of the capacitor C1l, which corresponds to the voltage between A- and GTO thyristor G11, the voltage detector 22a has a disadvantage in that the loss generated by the voltage detector 22a becomes large. That is, the voltage detector 22a includes resistors R11, . . . as shown in FIG. 9, for example.
This is realized by a voltage divider circuit using R12, but its power consumption is, for example, in the case of a large capacity GTO with a withstand voltage class of 2500V, the DC intermediate circuit voltage is used at about 1000V, so
If R11+Rtz=100KQ, the power consumption will be about 10W, which will require a large resistor of about 30 to 40W, resulting in a problem that the device will become larger. In addition, since the high voltage terminal voltage from the capacitor C1l is directly drawn into the voltage detector 22a, the voltage detector 22a
A long creepage distance is required to insulate the equipment inside a, which also causes the problem of increasing the size of the device. Therefore, it is an object of the present invention to reduce power consumption and creepage distance in a voltage detector, and to provide a small and highly reliable device of this type.

[Means for solving problems]

Detection of conduction and non-conduction of the qTO thyristor by its gate,
A monitoring means is provided that utilizes the voltage between the cathodes.

[Effect]

FIG. 5 is a waveform diagram showing the relationship between voltage and current of the GTO thyristor. Hereinafter, with reference to FIG. 5, the transition of the voltage between the gate and cathode of the GTO thyristor will be explained in particular.

As shown in the figure, the transition can be divided into the following seven periods.

(1) Period 7 (before time t): At this time gate (G)
A negative reverse bias voltage is applied between the cathode (K) and the GTO is in a cutoff state.

(2) Period 1: Gate forward current IQ is 10 of its peak value
% is reached at time t. to time t□ when the voltage VAK between the anode (A) and the cathode drops to 90%. This period is generally called the delay time.

(3) Period 2 near node-cathode voltage VAK is 90
The period from time t1 when the voltage drops to 10% to time t2 when the voltage drops to 10%. This period is commonly called the rise time.

Note that the sum of the delay time and rise time is generally called turn-on time.

(4) Period 3: The GTO is in a conductive state, the anode-cathode voltage VAK is several volts or less, and a predetermined anode current determined by the constants of the load circuit flows.

'(5) Period 4: The gate reverse current iG is 1 of its peak value.
Period from time t3 when it reaches 0% to time t4 when the anode current ■A drops to 90% of its peak value. This period is generally called the accumulation time.

(6) Period 5 near-node current IA has its peak value 090
The period from time t4 when the current drops to 10% to time t5 when the current drops to 10%.

This period is generally referred to as the downturn period.

(7) Period 6: Anode current IA is 10 of its peak value
The period from time t5 when the current drops to % until the current further decreases to the holding current. This period is generally called the tail period.

(8) Period 7 (after time t6): A negative reverse bias voltage of 1 is applied between the gate and the cathode, and the GTO 44 is in a cutoff state.

As described above, the gate cathode voltage VGK of the GTO thyristor is maintained during periods 1, 2, 3, and 4, that is, the turn-on process in which the non-conducting state changes to the conducting state, the conductive period, and the turn-off process in which the conductive state changes to the non-conducting state. During a part (accumulation period) of approximately +0.7V to +1.
On the other hand, a negative voltage is applied during periods 5.6 and 7, that is, a part of the turn-off process (falling period and tail period) and a non-conducting period. The magnitude of this negative voltage is generally selected to be approximately -2V to -18V. In addition, in FIG. 5, the gate cathode opening pressure VG for a short period of time from immediately after the start of period 6 until the gate current IG steeply approaches zero.
The reason why K is higher than the negative voltage applied during other periods is due to the voltage induced in the inductance of the gate lead wire.

This is because the voltage between the cathodes has increased to the avalanche voltage. In this way, the GTO thyristor game →
~ As long as the GTO is normal, the cathode voltage VGK is approximately +0.7V to +1.5V when conducting, and
A negative voltage is applied that is present when non-conducting. Therefore,
It can be seen that by monitoring this voltage it is possible to detect whether the GTO thyristor is conducting or non-conducting. Furthermore, if the GTO thyristor breaks down due to turn-off failure or the like, this can be detected because the gate and cathode are short-circuited and no negative voltage is applied.

〔Example〕

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2A is a time chart for explaining the ability to recover from an arm short-circuit accident in Fig. 1, and Fig. 2B is a protective operation when an arm short-circuit accident occurs. A time chart for explaining the above, and FIG. 3 is a configuration diagram showing a specific example of the low-voltage side circuit shown in FIG.

As is clear from FIG. 1, in this embodiment, the voltage detector (22a, . . . ) is a thyristor (Gll).

It is exactly the same as Figure 6 except that it is connected between the gate and cathode of . That is, the difference is that the voltage between the anode and the cathode is used in FIG. 6, whereas the voltage between the gate and the cathode is used in FIG. Therefore, since the operation 1 function is completely the same, the details will be omitted.

In Figures 2A and 2B, waveforms AI and A2 indicate the voltage between the gate and the cathode, so we can conclude that "Figure 7A,
It is different from that shown in FIG. 7B, and the two high-voltage side circuits shown in FIG. 3 are also different from the one shown in FIG. It's different.

Although the comparison circuit 23a in FIG. 3 is specifically shown as comprising a comparator 231 and a photocoupler 232, these are simply omitted in FIG.

FIG. 4 is a block diagram showing another embodiment of the present invention. This corresponds to Figure 8 explained earlier, but it is similar to Figure 1.
Since it is the same as that shown in the figure except that the voltage between the gate and cathode of the GTO thyristor is monitored, further explanation will be omitted.

〔Effect of the invention〕

According to this invention, since the conduction or non-conduction state is determined based on the interchamber pressure at G- of the GTO, the input voltage of the voltage detector is lower than that in the method of determining based on the interchamber pressure at A-. Therefore, it is possible to reduce the power consumption and the creepage distance in the voltage detector, and therefore it is possible to provide a small and highly reliable protection device. Furthermore, since the output line of the gate drive circuit can be shared as the input line of the voltage detector, there is an advantage that the wiring can be simplified.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2A is a time chart for explaining the arm short-circuit avoidance function in Fig. 1, and Fig. 2B is the same protection when an arm short-circuit accident occurs. Time chart for explaining the operation, Part 3
The figure is a block diagram showing a specific example of the high voltage side circuit shown in Figure 1, Figure 4 is a block diagram showing another embodiment of the present invention, and Figure 5 is a block diagram showing a specific example of the high voltage side circuit shown in Figure 1.
Waveform diagram showing the relationship between voltage and current of TO thyristor, No. 6
The figure is a configuration diagram showing the proposed protection device of the GTO thyristor inverter, and Figure 7A is a time chart for explaining the arm short circuit accident avoidance function in Figure 6).
7BIJ is also a time chart to explain the protective operation in the event of an arm short circuit accident, and Figure 8 is the proposed GT.
FIG. 9 is a block diagram showing another example of the O-thyristor inverter protection device. FIG. 9 is a block diagram showing a specific example of the high voltage side circuit shown in FIG. 6 or FIG. 8. Symbol explanation 1.11...Low voltage side logic operation circuit, 2A, 2B
...High voltage side circuit, 3 ... Short circuit thyristor, 4 ... Ignition unit, End ... Control circuit, 21a ... Gate drive circuit , 22a...
... Voltage detector, 23a... Comparison circuit, 23
1...Comparator, 232...Photocoupler, R4, R2, R11, R12s㇠21゜㇠22...
...Resistance, G11-G22...GTO thyristor, ANI-AN4...AND gate, 0
几1～OR3・・・・・・Or game), NOR・・・・
...Noah Gate. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki (:) () (
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Claims (1)

[Claims] 1) Monitoring conduction and non-conduction of individual gate turn-off (GTO) thyristors constituting a multi-phase inverter, and when one of the two GTO thyristors constituting each phase cannot be turned off. G prevents the other GTO thyristor from turning on to avoid an arm short-circuit accident.
TO thyristor inverter protection device, GTO
A protection device for a thyristor inverter, comprising a monitoring means for monitoring conduction or non-conduction of a thyristor using a voltage between its gate and cathode. 2) In the protection device according to claim 1,
If an arm short circuit accident occurs despite the above avoidance actions, turn on all the GTO thyristors that make up the inverter, or turn them off before the short circuit current reaches the maximum controllable current of the GTO thyristors. A protection device for a GTO thyristor inverter, which is characterized in that it protects an inverter.