JPS5999927A - Protecting system for controlled rectifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a protection method for a controlled rectifier, and particularly to a protection method for a controlled rectifier suitable for application to an inductive load with a large time constant.

[Technical background and problems of the invention]

It is known that controlled rectifiers, which have conventionally been configured to rely on controlled rectifying elements, use protection methods such as dart block, dart shift, and pi-i4 spare in the event of a failure such as an arm short circuit or a main pulse open phase. .

Here, the dart block is a protection interlock based on blocking the ignition pulse given to the control rectifier. On the other hand, the dirt shift is an operation in which the control firing angle is greatly delayed, the engine is operated in a reverse conversion region (firing angle of 90° to 180°), and energy on the DC side is regenerated to the AC side. In addition, Bino (spare) is a protective operation that simultaneously energizes a pair of controlled rectifiers connected to the same phase on the AC side to short-circuit the DC circuit.As a protection method for controlled rectifiers, Depends on the type of failure, these operations can be combined to perform operations ranging from gate shift to dirt pro, bypass, etc.
A common method is to perform protection interlocking from 67 to Dart Pro, instant dart block, etc., and finally switch to the AC side and open the interrupter.

Figure 1 shows the main circuit connection diagram of a 6-phase controlled rectifier.
In the figure, 1 is an AC bus bar, 2 is an AC interrupter, 36 is a rectifier transformer, 4 is a control rectifier that converts the output of the rectifier transformer into DC, 5 is a load, and 6 is a control of the control rectifier 4. A rectifier control circuit corresponding to the circuit, 7 is a control circuit that performs current control or voltage control based on the difference between the reference value and the detected value, and determines the firing angle of the rectifier, and is used to prevent failures of 8-point control rectifiers, rectifier transformers, etc. 11 shows each of the 11 protection linkage circuits that detect and determine protection linkage.

In such a configuration, DC power is supplied to the load 5 during normal operation, but if there is a failure in the control rectifier 4 that prevents it from properly controlling its output, such as a failure such as a failure such as an open phase in the control rectifier 4. If this occurs, the bypass pair and r-) shift cannot be protected, so conventionally, protection has been provided from the date block to the interrupter opening. By the way, if such a protection method is applied to a controlled rectifier that has a conductive load with a large time constant, the breaker must be opened before the alternating current reaches zero (current flows for about 1 second). ), there is a risk of damage to the interrupter. Also, if the current is cut off while a current exceeding a certain value is flowing (current cutoff of the interrupter), an overvoltage will occur due to the steep di/dt.
A problem occurs in that the control rectifier elements constituting the control rectifier 4 are destroyed.

In other words, if a phase loss occurs in the rectifier control circuit 6, according to the conventional protection method, the Dart Pro circuit breaker would open and the protection would be linked, but as shown in Fig. 1, If the time constant of the load 5 is large, it will take a long time for the DC current to decay, so the DC current will continue to flow.

For this reason, when performing a dirt block, the output voltage of the control rectifier 4 periodically generates positive and negative voltages.
Since the average value is zero, the DC current attenuates according to the time constant of the load and continues to flow to the two specific arms for a long time. In this way, if a large direct current continues to flow on the alternating current side, the current cannot be cut off even if the alternating current breaker 2 is opened, leading to a failure of the alternating current breaker 2.

Furthermore, if the AC breaker 2 is opened before the current reaches zero, the AC breaker 2 may interrupt the current, and as mentioned above, due to the sudden current change, overvoltage may be applied to the rectifier transformer 3. It will occur between the terminals, ie between the poles of the controlled rectifier. This overvoltage causes problems such as destruction of the control rectifying element.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a protection system for a controlled rectifier that eliminates the drawbacks of the prior art described above and can smoothly protect the controlled rectifier when it breaks down.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention is provided with a current zero detection circuit, and directly or indirectly detects that the current has become zero, and opens the AC interrupter. .

[Embodiments of the invention]

FIG. 2 shows a block diagram of an embodiment of the present invention. FIG. 2 shows a current transformer 1 and a current transformer 11, which are used to detect alternating current, in contrast to FIG.
Current zero detection circuit 12 that detects that the next current has become zero
, the protection interlocking circuit β and the current zero detection circuit 12 output from the 5- signals are added to the AND circuits 1 and 9.

Next, the present invention having the above configuration will be explained in detail. now,
If a failure such as pulse loss occurs in the rectifier control circuit 6, the protection interlock circuit 8 determines the protection interlock of opening the breaker from the Jigood block. Even if the ignition/P pulse is stopped by the dirt block signal output from the protection interlocking circuit, the DC current will attenuate according to the time constant of the load. Continue to flow into the arm. Next, the current transformer 11 and zero current detection circuit 12 detect whether the current on the AC side is zero or
It detects that the value has fallen below a value that will not cause any actual damage even if the interrupter is opened, and outputs a signal "1". This signal and the logic signal @1# output from the protection interlocking circuit 8 are input to the AND circuit 13, and its output is the logic signal '1
'', an AC circuit breaker 2 is inputted with an open signal, and the AC circuit breaker 2 is opened.

As mentioned above, in the event of a failure, if the breaker is opened after dart blocking and the AC current is zero or below a value that does not cause any harm even if the breaker is opened, the breaker's polarity will The problem of long-term arcing and destruction of the circuit breaker does not occur. Further, since the current is sufficiently small, no overvoltage is generated in the controlled rectifier, and the controlled rectifier can be smoothly protected.

In the configuration shown in FIG. 2, the same effect can be obtained even if zero current detection is performed on the secondary side of the rectifier transformer 3.

FIG. 3 is a block diagram of a controlled rectifier according to still another embodiment of the present invention. In the figure, 14 is a delay circuit, and 15 is an OR circuit.

In the above-mentioned configuration, if a failure such as a main pulse open phase occurs in the rectifier control circuit 6, the protective interlocking circuit 8 determines the protective interlocking of opening the breaker from the Q gate block, and the ignition pulse is blocked. Ru. Next, a breaker release signal is inputted from the protection interlocking circuit 8 to the AND circuit 13 and the delay circuit 14. When the opening signal of the circuit breaker 1 is input to the delay circuit 14, the output of the delay circuit becomes logic "1#" after a suitably set time has elapsed in the delay circuit 14.The circuit breaker opening signal becomes logic "1#". The signal is converted into alternating current via the sum circuit 15 and input to the interrupter 2.

Next, the current transformer 1 and the current zero detection circuit detect that the current on the alternating current side is zero or has dropped below a value that will not cause any actual damage even if the breaker is opened, and outputs the logic signal “1#”. is outputted to the AND circuit 13, and by ANDing it with the breaker open signal "1" output from the protection interlocking circuit 8, the output becomes a logic signal 11111, which causes alternating current and an open signal is input to the interrupter 2. The AC breaker 2 is opened by the earlier signal of the delay circuit 14 and the AND circuit 13.The above circuit can achieve the same effect as in the case of FIG. At the same time, the maintenance of the controlled rectifier becomes more reliable.

Incidentally, it goes without saying that the set delay time of the delay circuit 14 is set to the time until the current of the control rectifier becomes zero, depending on the maximum fault current, rated voltage, DC reactor value, etc.

〔Effect of the invention〕

As described above, according to the present invention, even if a failure such as a phase loss occurs in the control rectifier, the control rectifier is date-blocked and the current on the primary or secondary side of the rectifier transformer is Since the AC breaker is opened after confirming that the voltage has become zero, it is possible to obtain a protection method for the control rectifier that eliminates destruction of the AC breaker and generation of overvoltage to the control rectifier.

[Brief explanation of drawings]

Fig. 1 is a main circuit connection diagram of a six-phase controlled rectifier, Fig. 2 is a professional diagram of a controlled rectifier according to one embodiment of the present invention, and Fig. 3 is a diagram of a controlled rectifier according to another embodiment of the present invention. It is a block diagram. DESCRIPTION OF SYMBOLS 1... AC bus, 2... AC breaker, 3... Rectifier transformer, 4... Control rectifier, 5... Load, 6
... Rectifier control circuit, 7... Control circuit, 8... Protection interlocking circuit, 11... Current transformer, 12... II current zero detection circuit 13... AND circuit, 14...・Delay circuit,
15... Theory 9- Reasoning circuit. 10-

Claims (1)

[Claims] In a controlled rectifier configured by controlled rectifying elements, when a failure occurs, it is determined whether the current in the controlled rectifier has become zero either directly or by prediction over time, and the AC breaker is opened. protection method for controlled rectifiers.