JPH0767228B2 - Abnormality diagnosis device for thyristor element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thyristor element abnormality diagnosing apparatus for diagnosing abnormality of a thyristor element used in a power conversion device.

[Conventional technology]

Abnormalities of the thyristor element include a breakdown phenomenon and a breakover phenomenon. Among them, the breakdown phenomenon is a state in which the thyristor element is in a conductive or low state when the blocking ability of the thyristor element is lost on the forward side and the reverse side. It is a phenomenon that becomes equal to resistance, and the breakover phenomenon is
This is a phenomenon in which the thyristor element becomes equivalent to a diode operation when the forward blocking ability of the thyristor element is lost.

As a conventional example for diagnosing such abnormality of the thyristor element, a fuse is inserted in series with the thyristor element in the circuit,
A method of blowing a fuse with a large current that flows when a breakdown phenomenon or a breakover phenomenon occurs, or the leakage current in the blocking state of a thyristor element is measured, and the magnitude of this leakage current determines the breakdown phenomenon or the breakover phenomenon. There is a method for detecting the occurrence (for example, JP-A-62-80567).

However, in the method of diagnosing the abnormality of the thyristor element due to the blow of the fuse, if the impedance of the circuit is high even if the breakdown and breakover phenomena of the thyristor element occur, the current flowing in the circuit is small and the fuse is blown. There was an unsolved problem of not doing it. Further, in the method of detecting an abnormality in the thyristor element based on the leakage current, it is necessary to disconnect the thyristor element from the circuit, so that there is an unsolved problem that it is inevitable that the circuit will be out of power for a long time.

Therefore, in order to solve such an unsolved problem, current does not flow in the circuit before the thyristor element is ignited, but if a breakdown phenomenon and a breakover phenomenon occur in the thyristor element, before the ignition. There is a conventional example in which an abnormality of a thyristor element is detected by detecting this current because of the flow of the current.

[Problems to be Solved by the Invention]

However, in the conventional method of detecting the breakdown phenomenon and the breakover phenomenon from the ignition state of the thyristor element,
There is a problem in that a device for detecting the ignition state of the thyristor element is required in addition to the current detector.

Further, in the method of detecting the variation of the currents on the AC side and detecting the abnormality of the thyristor element, the current imbalance occurs when the control of the thyristor element changes suddenly (for example, during deceleration, when the current changes by 200%). As a result of erroneously recognizing this imbalance as a variation in phase currents on the AC power supply side, there is a problem that an abnormality in the thyristor element cannot be detected reliably.

In order to solve such conventional problems, the present invention aims to provide an abnormality diagnosing device for a thyristor element capable of reliably detecting an abnormality in a thyristor element without requiring a special device. And

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides an abnormality of a thyristor element for diagnosing an abnormality of a thyristor element in a power conversion device having a bridge circuit of thyristor elements 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 a phase delay angle of the thyristor element in a range in which an operating current does not flow in the power converter, and a current arranged in a line between an input side of the power converter and an AC power source. A detector, and an abnormality detecting unit that determines that the thyristor element is in an abnormal state when the current detected by the current detector is equal to or more than a predetermined set current in a state where the phase delay angle is set by the setting unit. It is characterized by that.

[Action]

According to the present invention, a thyristor of a power converter is provided in a phase delay angle range (for example, a range of 130 ° to 150 °) in which no current is supplied to the DC load of the power converter, that is, during a stop period when the DC load is a DC motor. When the elements are in a normal state, no current flows through these thyristor elements, so the detected current detected by the current detector is zero, but any one of the thyristor elements has a breakdown phenomenon or a breakover phenomenon. When they occur, an abnormal current resulting from these is detected by the current detector. When this abnormal current is greater than or equal to a predetermined current, the abnormality detecting means determines that the thyristor element is in an abnormal state. Therefore, it is possible to surely detect the abnormality of the thyristor element only by detecting the abnormal current without requiring a special device.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

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

In the figure, 1 and 2 are thyristor elements, and a rectifier circuit is configured by connecting three series circuits in which two sets of thyristor elements are connected in series to form a rectifier circuit, and connection points of the thyristor elements connected in series. A three-phase AC power supply 22 is connected to each. That, U-phase of the AC power supply to the connection point of the thyristor element U _P and U _N are connected, V-phase of the AC power supply to the connection point between the thyristor element V _P and V _N are connected, thyristor element W _P and W _N The W phase of the AC power supply is connected to the connection point with.

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. Among the thyristor elements, 1 is an abnormal thyristor element in which a breakdown phenomenon or 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 on the AC power supply side of the device of the above embodiment 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 is included in the rectifier 221 for rectifying the abnormal current detected by the coil 20, and the abnormal current. A noise filter 6 for removing noise components, an isolation amplifier 7 for preventing contact, a comparator 8 for comparing whether or not the detected abnormal current value is larger than a set value, and this comparator. 8
An abnormal current that exceeds the set value is detected with and the detection circuit 10 that records the current value and the alarm device 12 that generates an alarm sound when the abnormal current is detected by this detection circuit 10 are connected in series. ing. Reference numeral 9 connected to the detection circuit 8 is a current setting device that outputs a current setting value to be compared with the abnormal current, and reference numeral 11 is a reset circuit for erasing the abnormality detection content of the detection circuit 10.

In the device of this embodiment, an abnormal current is detected when the operating condition of the device is not established. That is, the abnormal current and the operating current are distinguished by setting the phase delay angle of each thyristor element by the gate control circuit of the thyristor element (not shown) so that the operating current due to the forward conversion or the reverse conversion does not flow in the circuit. In this state, the abnormal current is detected.

The inventors of the present invention have conducted various studies, and in three-phase rectification, if the phase delay angle α of the thyristor element is set between 130 ° and 150 °, current will flow in the circuit when all the thyristor elements are normal. Although it does not flow, it has been found that when an abnormality occurs in the thyristor element, an abnormal current flows within the above range.

Next, the operation of this embodiment will be described with reference to FIG. 2 which is a motion wave diagram of FIG.

In FIG. 1, a gate control circuit (not shown) sets the phase delay angle α to 150 ° at which the operating condition is not satisfied. At this time, if the breakdown phenomenon occurs in the thyristor element 1 and the other thyristor elements 2 are normal, as shown in FIG. 2, when the thyristor element V _P is in the ignition state (FIG. 2A), Since the V-phase voltage is higher than the U-phase voltage and the thyristor element 1 is a conductor, the breakdown current 4 flows from the V-phase side of the AC power supply 22 to the U-phase side. Similarly, if a breakover phenomenon occurs in the thyristor element, as shown in FIG. 2, when the thyristor element V _N is in the ignition state (FIG. 2B), the U-phase voltage is larger than the V-phase voltage, Moreover, since the thyristor element 1 operates as a diode, it can be seen that the breakover current 5 flows from the U phase side to the V phase side.

The abnormal currents 4 and 5 flowing through each phase side of the AC power supply 22 are detected by the detection coil 20 and rectified by the rectifier 21 to reach the noise filter 6, and the noise component is removed, and then the insulation amplifier 7 is passed through. It reaches the comparison circuit 8. The abnormal current may be detected by the peak hold method or the RMS method.

In the comparison circuit 8, the current value set by the current setting device 9 is compared with the detected abnormal current value. As a result of this comparison, an abnormal current exceeding the set value is detected by the detection circuit 10, and this abnormal current value is recorded. Detection circuit
In 10, when an abnormal current is detected, the alarm circuit 12 sounds an alarm for a predetermined time.

The content of the abnormal current detection of the detection circuit 10 is the reset circuit 11
It is more erasable. That is, it is possible to prepare for the next detection because the detection content is erased by a manual reset by a person's judgment or an automatic reset when the power conversion device enters the operating state.

According to the abnormality diagnosing device for a thyristor element according to the present embodiment, it is possible to reliably detect an abnormality in the thyristor element with a simple configuration without modifying any existing control circuit. Moreover, since it is not necessary to remove each thyristor element from the circuit in which it is incorporated, an abnormality in the thyristor element can be easily detected, and troubles due to incorrect connection of the removed thyristor element are eliminated.

Next, specific examples will be described.

Five sets of the diagnostic device according to the present embodiment were installed in a power converter of a cold rolled tandem mill motor and 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, the abnormality was detected twice, and as a result of the investigation, one breakdown element and one breakdown element were found.

This abnormality in the thyristor element occurred at the start of regular inspection and repair work, and because it was during roll preparation two hours before operation, the operating loss due to plate breakage due to abnormal current flow was avoided in advance. We were able to.

[Effects of the Invention] As described above, according to the present invention, since it is possible to diagnose an abnormality in a thyristor element by simply detecting an abnormal current flowing in the circuit based on an abnormality in the thyristor element, a special device is required. The abnormality of the thyristor element can be detected easily and surely.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an operation waveform diagram of FIG. 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. A setter, 10 is a detection circuit, 11 is a reset circuit, and 12 is an alarm device.

Claims (1)

[Claims] 1. A thyristor element abnormality diagnosing device for diagnosing abnormality of a thyristor element in a power converter having a bridge circuit of thyristor elements, the input side of which is connected to an AC power source and the output side of which is connected to a DC load. Setting means for setting the phase delay angle of the thyristor element within a range in which no operating current flows through the device, a current detector arranged on the line between the input side of the power converter and the AC power supply, and the setting means. The thyristor element is provided with an abnormality detecting means for determining that the thyristor element is in an abnormal state when the current detected by the current detector is equal to or more than a predetermined set current in a state where the phase delay angle is set. Abnormality diagnosis device.