JPH01278227A - Anomaly diagnostic device for thyristor element - Google Patents

Abstract

PURPOSE:To detect anomaly for sure without providing any special device, by judging that the thyristor elements are in an anomalous state when the detected current is not less than the predetermined value under the condition where the phase delay angle of thyristor elements are set within the range in which no driving current will flow. CONSTITUTION:By a gate control circuit the phase delay angle is set at 150 deg. where no driving condition holds. On this occasion, a breakdown phenomenon is observed to a thyristor element 1, where, suppose a thyristor element 2 is normal, the breakdown circuit 4 will flow from V-phase side to U-phase side of an AC power source 22, since the V-phase voltage is larger than the U-phase one and that the thyristor element 1 is a conductor when the thyristor element VP is in the ignition state. Anomalous current 4 is then detected by a detecting coil 20. After it is rectified by a rectifier 21, it gets to a comparator 8, where it is compared with the current value set by a current setter 9, so that the anomaly is detected by a detection circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thyristor element abnormality diagnosing device for diagnosing an abnormality in a thyristor element used in a power conversion device.

[Conventional technology]

Abnormalities in thyristor elements include breakdown phenomenon and breakover phenomenon. Of these, breakdown phenomenon is a state in which the thyristor element has lost its stopping ability on both the forward and reverse sides, and the thyristor element is a conductor or The breakover phenomenon is a phenomenon in which the thyristor element loses its forward blocking ability and the thyristor element behaves like a diode.

As a conventional example of diagnosing abnormalities in such thyristor elements, a fuse is inserted in series with the thyristor element in the circuit,
There are methods for blowing fuses using large currents that flow when breakdown and breakover phenomena occur, and methods for measuring leakage current in the blocking state of thyristor elements, and determining whether breakdown and breakover phenomena occur based on the magnitude of this leakage current. There are methods for detecting the occurrence (for example, Japanese Patent Laid-Open No. 62-80567).

However, in the method of diagnosing abnormalities in thyristor elements due to fuse blowouts, if the impedance of the circuit is large even if the breakdown or breakover phenomenon of the thyristor elements occurs, the current flowing in the circuit is small, so the fuse will blow. There was an unresolved issue of not doing so.

Furthermore, in the method of detecting abnormality in a thyristor element based on leakage current, it is necessary to disconnect the thyristor element from the circuit, so there is an unresolved problem that the circuit inevitably experiences a long power outage.

Therefore, in order to solve such unresolved issues, no current flows in the circuit before the thyristor element is fired, but when a breakdown phenomenon or breakover phenomenon occurs in the thyristor element, the current flows before the thyristor element is fired. Because of the current flow, there is a conventional example of detecting this current to diagnose abnormalities in the thyristor element.

[Problem to be solved by the invention]

However, with the conventional method of detecting breakdown and breakover phenomena from the firing status of the thyristor element,
There is a problem in that, in addition to the current detector, a separate device for detecting the firing status of the thyristor element is required.

In addition, in the method of detecting abnormalities in the thyristor element by detecting variations in the current of each phase on the AC side, current imbalance occurs when the control of the thyristor element suddenly changes (for example, during deceleration, when the current changes by 200%, etc.). As a result of misinterpreting this imbalance as a variation in the current of each phase on the AC power supply side, there is a problem in that abnormalities in the thyristor elements cannot be reliably detected.

In order to solve such conventional problems, an object of the present invention is to provide a thyristor element abnormality diagnostic device that can reliably detect abnormalities in a thyristor element without requiring a special device. shall be.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for diagnosing an abnormality in a thyristor element in a power conversion device having a bridge circuit of a thyristor element whose input side is connected to an AC power source and whose output side is connected to a DC load. In the diagnostic device, a setting means for setting the phase delay angle of the thyristor element within a range in which no operating current flows through the power converter, and a current disposed in a line between the input side of the power converter and the AC power supply. a detector; and abnormality detection means that determines that the thyristor element is in an abnormal state when the current detected by the current detector is equal to or higher than a predetermined set current while the phase delay angle is set by the setting means. It is characterized by this.

[Effect]

In this invention, the phase delay angle range (for example, 130° to 150°
° range), that is, during a stop period when the DC load is a DC motor, no current flows through the thyristor elements of the power conversion device when they are in a normal state, and therefore no current is detected by the current detector. Although the detected current is zero, if a breakdown phenomenon or breakover phenomenon occurs in any of the thyristor elements, the abnormal current caused by this is detected by the current detector. When this abnormal current is equal to or higher than a predetermined current, the abnormality detection means determines that the thyristor element is in an abnormal state. Therefore, an abnormality in the thyristor element can be reliably detected simply by detecting the abnormal current without requiring any special equipment.

〔Example〕

Next, one embodiment of the present invention will be described based on the accompanying drawings.

FIG. 1 shows a circuit diagram of a power conversion device according to an embodiment of the present invention.

In the figure, 1.2 is a thyristor element, and a series circuit in which two sets of thyristor elements are connected in series is connected in parallel to form a rectifier circuit. A three-phase AC power source 22 is connected to each. That is, the U phase of the AC power supply is connected to the connection point between the thyristor elements U, and the thyristor elements V,
The V-phase of the AC power supply is connected to the connection point between and ■8, and the thyristor element WPl! :The W phase of the AC power supply is connected to the connection point with WN.

A DC load (for example, a DC motor) 3 is connected between the cathode side of each thyristor element and the anode side of each thyristor element. One of the thyristor elements is an abnormal thyristor element in which a breakdown phenomenon or a breakover phenomenon has occurred, and 2 is a normal thyristor element in which such a phenomenon has not occurred.

A thyristor abnormality diagnosis circuit 30 is connected to each phase of the AC power supply side of the above embodiment device via a current detection coil 20.

This thyristor abnormality diagnosis circuit 30 detects an abnormal current flowing to the AC power supply 22 side when the thyristor element is abnormal, and includes a rectifier 21 for rectifying the abnormal current detected by the coil 20, and a rectifier 21 for rectifying the abnormal current detected by the coil 20. A noise filter 6 for removing noise components, an isolation amplifier 7 for preventing cross contact, a comparator 8 for comparing whether the detected abnormal current value is larger than a set value, and this comparator. A detection circuit 10 detects an abnormal current exceeding a set value at 8 and records the current value, and an alarm 1 generates an alarm when the abnormal current is detected by this detection circuit 10.
2 are connected in series.

Note that 9 connected to the detection circuit 8 is a current setter that outputs a current setting value to be compared with the abnormal current, and 1) is a reset circuit for erasing the contents of abnormality detection in the detection circuit 10. .

In the device of this embodiment, abnormal current is detected in a state where the operating state of the device is not established. That is, in order to prevent the operating current associated with forward conversion or inverse conversion from flowing through the circuit, the abnormal current and the operating current are distinguished by setting the phase delay angle of each thyristor element using a gate control circuit for the thyristor element (not shown). abnormal current is detected.

The present inventors conducted various studies and found that in three-phase rectification, the phase delay angle α of the thyristor element was set to 130 @ ~ 1
It has been found that when the thyristor elements are set between 50'' and all the thyristor elements are normal, no current flows through the circuit, but when an abnormality occurs in the thyristor elements, an abnormal current flows within the above range.

Next, the operation of this embodiment will be explained using FIG. 2, which is a dynamic wave diagram of FIG. 1.

In FIG. 1, a gate control circuit (not shown) sets the phase delay angle α to 150°, at which the operating conditions are not met. At this time, a breakdown phenomenon occurs in the thyristor element 1,
Assuming that this thyristor element 2 is normal, as shown in FIG. 2, when the thyristor element V is in the firing state (
Figure 2 A), the V-phase voltage is greater than the U-phase voltage, and
Since the thyristor element 1 is a conductor, a breakdown current 4 flows from the "■ phase" side of the AC power supply 22 to the U phase side.Similarly, if a breakover phenomenon occurs in the thyristor element, the breakdown current 4 is shown in FIG. As shown, when the thyristor elements V and 4 are in the firing state (Fig. 2B), the U-phase voltage is larger than the V-phase voltage, and the thyristor element 1 is in diode operation, so there is no breakover. It can be seen that current 5 flows from the U-phase side to the V-phase side.

The abnormal current 4.5 flowing through each phase side of the AC power supply 22 is detected by the detection coil 20, rectified by the rectifier 21, then reaches the noise filter 6, and after the noise component is removed, it is passed through the insulation amplifier 7. The comparison circuit 8 is reached. Note that abnormal current detection may be performed using a peak hold method or an RMS method.

This comparison circuit 8 compares the current value set by the current setting device 9 and the current value of the detected abnormal current. As a result of this comparison, an abnormal current exceeding the set value is detected in the detection circuit IO, and this abnormal current value is recorded. When the detection circuit 10 detects an abnormal current, the alarm circuit 12 emits an alarm sound for a predetermined period of time.

The contents of abnormal current detection by the detection circuit 10 can be erased by a reset circuit 1). That is, the detected contents are erased by manual reset based on human judgment or automatic reset when the power conversion device enters the operating state, making it possible to prepare for the next detection.

According to the thyristor element abnormality diagnosing device according to this embodiment, there is no need to modify existing various control circuits, and an abnormality in a thyristor element can be reliably detected with a simple configuration. Furthermore, since there is no need to remove the thyristor element from the circuit in which it is incorporated, abnormalities in the thyristor element can be easily detected, and troubles due to incorrect connections of the removed thyristor element are eliminated.

Next, specific examples will be described.

Five sets of the diagnostic apparatus according to the present example were installed in a power converter for a cold-rolled tandem mill motor, and were used for one year.

The abnormal current setting value of the current setting device 9 was set as shown in Table 1.

As a result, two abnormalities were detected, and as a result of the investigation, one breakdown element and one breakover element were discovered.

This abnormality in the thyristor element occurred at the beginning of periodic inspection and repair work, and since it was during roll preparation two hours before operation, it was possible to avoid operational losses due to plate breakage due to abnormal current flow. We were able to.

Table 1 [Effects of the Invention] As explained above, according to the present invention, an abnormality in a thyristor element can be diagnosed simply by detecting an abnormal current flowing in a circuit based on an abnormality in the thyristor element, so a special device is not required. Abnormalities in thyristor elements can be easily and reliably detected without the need for

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an operational waveform diagram of FIG. 1. In the figure, 1 is an abnormal thyristor element, 2 is a normal thyristor element, 3 is a DC load, 4 is a breakdown current, 5 is a breakover current, 6 is a noise filter, 7 is an isolation amplifier, 8 is a comparator, and 9 is a current Setting device, 10 is a detection circuit, 1
) indicates a reset circuit, and 12 indicates an alarm.

Claims (1)

[Claims] (1) In a thyristor element abnormality diagnosing device for diagnosing an abnormality in a thyristor element in a power converter having a bridge circuit of a thyristor element whose input side is connected to an AC power source and whose output side is connected to a DC load, the power converter a setting means for setting the phase delay angle of the thyristor element in a range in which no operating current flows; a current detector disposed on the line between the input side of the power converter and the AC power supply; An abnormality in a thyristor element, comprising an abnormality detection means that determines that the thyristor element is in an abnormal state when the current detected by the current detector is equal to or higher than a predetermined set current with a delay angle set. Diagnostic equipment.