JP2000262061A - Thyristor rectifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an element destruction phenomenon at the time of small current by discriminating whether or not a setting value to a current setter is a set lower-limit current value or less and, if so, shifting the phase angle of gate trigger pulse to such a maximum angle that rectifying output becomes zero. SOLUTION: When current lower setting operation is performed with a current setter (S101), a current controller delays the operation of a rectifier, following its setting value, so that real current is decreased (S102). This operation is repeated until the real current reaches a current value A [kA] which causes current interruption at the time of small current. When the real current is A [kA] or less (S103 Yes), the control angle of a thyristor is shifted until αmax which causes the real current to become zero is reached. In stopping the operation in this way, the output current of the rectifier 2 become zero immediately from A [kA]. Therefore, the operation is stopped without experience of the operating state of small current, thereby eliminating an interruption phenomenon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to current control of a thyristor rectifier.

[0002]

2. Description of the Related Art Conventionally, there is a thyristor polyphase rectifier having a configuration shown in FIG. In the figure, 1 is a rectifier transformer, 2 is a rectifier composed of thyristor elements, 3 is a current control device, and 4 is a current setting device. At the time of the small current operation below the current intermittent limit level in the rectifier 2, the switching loss of the thyristor becomes large due to partial ignition due to partial ignition in relation to the other system rectifier and the counter voltage on the load side,
The thyristor element may be destroyed due to a local temperature rise. In addition, during small current operation, there is a possibility that an element may be destroyed due to an output voltage fluctuation due to the rectifier DC-side equipment and an element firing timing.

[0003] However, since the DC-side equipment of the thyristor rectifier is normally operated continuously near the rated output of the rectifier, it does not operate at the small current as described above. The operation with a small current is performed when the equipment is stopped by inspection. In that case, in order to safely stop the equipment, the output current is reduced to zero and then the circuit breaker is opened. Also, when the circuit breaker is turned on when the equipment is restored, the output current is gradually increased from zero in accordance with the condition of the load equipment in order to similarly start the operation of the equipment safely. At these times, the thyristor rectifier is operated with a small current.

Therefore, conventionally, a bias has been provided for the current setting in order to prevent a small current operation which causes these problems. That is, the lower setting limit of the current setter 4 is set to A [k
A], as shown in FIG. 6, the actual current of the rectifier 2 does not become smaller than A [kA] even if the set value is changed downward from the current value during normal operation. Also,
As shown in FIG. 7, even when the current value is increased, the current value is increased from the minimum value A [kA].

[0005]

However, when the bias amount of the current set value is increased in the above operation, there is a problem that the thyristor element is damaged by a surge voltage when the circuit breaker is opened. Conversely, if the amount of bias is reduced, then there is a problem in that the counter voltage fluctuates and the effect of applying the bias cannot be obtained. Therefore, an object of the present invention is to provide a thyristor rectifier capable of preventing an element destruction phenomenon at a small current.

[0006]

In order to solve the above problems, the present invention relates to a thyristor element, a current setting device for setting an output current value from the thyristor device, and a setting of the current setting device. A thyristor rectifier having a current control device for controlling a phase angle of a gate trigger pulse to a thyristor element based on a means for storing a current lower limit set value equal to or greater than a preset small current operation range; Means for judging whether or not the set value to the heater is equal to or less than the current lower limit set value, and shifting the phase angle of the gate trigger pulse to the maximum angle at which the rectified output becomes zero if the current value is equal to or less than It is characterized by the following.

In general, a thyristor rectifier generally has
Since continuous operation is not performed at an output of 50% or less, the current is forcibly reduced to zero by shifting the control angle of the thyristor to the αmax side for the current setting at a small current level that causes current interruption at a small current. Thus, partial firing can be prevented. As a result, it is possible to prevent element destruction due to a local temperature rise of the thyristor.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The basic configuration of the embodiment is the same as that shown in FIG. Figure 1,
FIG. 2 is a flowchart showing the operation of the embodiment of the present invention. FIG. 1 shows an operation when the operation is stopped by decreasing the current set value during operation of the thyristor rectifier. First, when a current value setting operation is performed by the current setting device 4 (step 101), the current control device 3 controls the rectifier 2
The actual current decreases by delaying the phase angle of the gate trigger pulse (control angle of the thyristor) to the set value (step 102).

This operation is continued until the actual current reaches a current value A [kA] at which current interruption occurs at the time of a small current, and when the actual current falls below A [kA] (step 103Ye).
s) The thyristor control angle is shifted to αmax at which the actual current becomes zero (steps 104 and 105). FIG.
The relationship between the set value and the actual current when the operation is stopped is shown. When the operation is stopped in this way, the output current of the rectifier 2 immediately becomes zero from A [kA], so that the operation is stopped without passing through the small current operation state, and the intermittent phenomenon occurs. Disappears. Note that this αmax is usually 130 to 150
°.

FIG. 2 shows an operation for starting operation of the thyristor rectifier during a stop. First, when a current value setting operation is performed by the current setting device 4 (step 20).
1) The current control device 3 keeps the thyristor control angle on the αmax side until the set value reaches the current value A [kA] at which the current interruption at the time of small current ends, and keeps the rectifier 2 from outputting current. (Steps 202 No, 203, 20
1). Next, when the set value reaches A [kA] (Step 202 Yes), the standby on the αmax side of the thyristor control angle is canceled, and the operation is started with the control angle corresponding to the set value (Step 204).

As a result, thereafter, the output current of the rectifier 2 increases following the set value of the current setter 4 (step 205). FIG. 4 shows the relationship between the set value at the start of the operation and the actual current. Even when the operation is started in this manner, the output current of the rectifier 2 immediately changes from zero to A [kA], so that the operation is started without passing through the small current operation state, and the intermittent phenomenon does not occur. Disappears. The current value at which the intermittent phenomenon occurs depends on the rated output current of the rectifier.
Since it is a very small value of 5 to 10%, there is no problem even if the operation at A [kA] or less cannot be performed.

[0012]

As described above, according to the present invention, when the range of the current set value is in the range of the small current operation, the phase angle of the gate trigger pulse becomes maximum and the output current becomes zero. This prevents element destruction during small current operation.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation of an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a set value and an actual current in the case of FIG.

FIG. 4 is a graph showing a relationship between a set value and an actual current in the case of FIG.

FIG. 5 is a diagram showing a basic configuration of a thyristor rectifier according to the embodiment.

FIG. 6 is a graph showing the operation of the conventional example.

FIG. 7 is a graph showing the operation of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectifier transformer 2 Rectifier 3 Current control device 4 Current setting device

Claims (1)

[Claims] 1. A thyristor element, a current setting device for setting an output current value from the thyristor device, and a current for controlling a phase angle of a gate trigger pulse to the thyristor element based on the setting of the current setting device A thyristor rectifier having a control device and means for storing a current lower limit set value that is equal to or greater than a preset small current operation range; and whether a set value to the current setter is equal to or less than the current lower limit set value. Means for judging whether or not the phase angle of the gate trigger pulse is shifted to the maximum angle at which the rectified output becomes zero in the following cases: