JPH0678451A - Method and apparatus for detecting abnormality of thyristor - Google Patents

Abstract

PURPOSE:To identify a defective thyristor without disassembling an apparatus, by applying an AC voltage to a built-in thyristor, measuring a current across the thyristor, and detecting a defective built-in thyristor on the basis of a difference in current that is in accord with a difference in impedance of the thyristor circuit. CONSTITUTION:After an AC voltage is applied to terminals 16A and 16B connected to both ends of a built-in thyristor, a current across the thyristor is measured with selected ammeters 17A and 17B. In a cycle-converter circuit including a transformer, a current in the circuit is decreased due to a reactance factor of the transformer, so a difference in impedance in a circuit to be checked corresponds to a position of a deteriorated or defective thyristor. Consequently, the deteriorated or defective thyristor is discriminated on the basis of a difference in measured current values, and the defective thyristor can be specified without disassembling an overall apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thyristor element abnormality detecting method and apparatus used in a cycloconverter.

[0002]

2. Description of the Related Art A cycloconverter is a power supply device for controlling the speed of an AC motor, which directly exchanges a commercial frequency with an alternating current of a different frequency without exchanging it with a direct current. Due to the recent technological trends, the introduction of cycloconverter devices for large electric motors tends to be promoted in the future.

Conventionally, the following method has been known as a method for discriminating an abnormality of the thyristor element itself used in a cycloconverter of this type, for example, a deteriorated product or a defective product.

(1) A method of directly measuring resistance with a tester. (2) A method of measuring the megΩ value (meguohm) with an insulation resistance meter (megger). (3) A curve tracer method in which a DC voltage is applied to the thyristor element alone to measure the change in leakage current. (4) The method disclosed in JP-A-62-80567. (5) The method disclosed in JP-A-1-278227.

[0005]

However, the above (1)
With the method, if there is a circuit around a transformer with low DC resistance, such as a cycloconverter, measurement cannot be performed without disassembling the device. In the method (2), the scale scale was too large, the pointer was almost 0, and there was no difference, making it impossible to determine. The method (3) requires disassembling the device, and requires a great deal of time because the structure of the cycloconverter is complicated.

On the other hand, in the method (4), when a complicated circuit such as a cycloconverter is provided and a circuit around the transformer is provided, the number of measurement points is large and the applied voltage is high. It is difficult and it is expected that the measurement will take a lot of time. Further, in the method (5), the detection circuit is incorporated in a state where the power source of the device is activated, and therefore, it is necessary to attach the detection circuit to each device, which further complicates the circuit of the cycloconverter having a complicated circuit. That means a major remodeling is necessary.

Therefore, the main problems of the present invention are to identify a defective thyristor without disassembling the device, to enable measurement with a simple device, to simplify the measuring method and to shorten the measuring time, to stress the circuit components. It is to be able to measure safely without giving.

[0008]

According to the method of the present invention which has solved the above-mentioned problems, when an abnormality of a thyristor element group in a cycloconverter is detected, an AC voltage is applied to both ends of a certain thyristor in a built-in state so that both ends flow. It is characterized in that the current value is measured and the abnormal thyristor element is detected based on the difference in the current value based on the difference in the impedance of the circuit including the thyristor.

Further, the device of the present invention includes a plug terminal to a commercial AC power source, an AC voltage transformer, a voltmeter after transformation, and a connection terminal for applying the transformed AC voltage to both ends of the thyristor element. And an ammeter for measuring a current flowing through both ends of the thyristor element, which are integrated with each other.

[0010]

FIG. 1 shows an example of a main circuit of a cycloconverter device. After transformation by a transformer T, UA to ZB drive an induction motor M through a circuit composed of a thyristor element group. There is.

Here, in order to discriminate the abnormal thyristor element, the thyristor element UA is now used without disassembling the device and using the conventional tester or insulation resistance tester as it is.
Suppose you have measured both ends of. At this time, there are some phenomena of element failure, but the phenomenon that the resistance between A (anode) and K (cathode) decreases to 50-60Ω or less is often seen, and if this is detected, it can be immediately identified. However, even if there is an abnormality in the thyristor element ZB, since the circuit around the transformer T is formed,
After all, the above tester or insulation resistance tester cannot identify the abnormal thyristor element. The same applies when an abnormality occurs in another element.

In order to identify this intentionally, it is necessary to disassemble and measure each thyristor element, and at that time, at least one side must be trimmed. In this case, the cycloconverter has a complicated structure, which requires a great deal of trouble.

On the other hand, according to the present invention, when an AC voltage is applied to both ends of a certain thyristor in the assembled state and the value of the current flowing through the both ends is measured, the reactance component of the transformer in the circuit around the transformer of the cycloconverter is measured. Therefore, the current value decreases, so that the impedance of the circuit including the thyristor being measured is deteriorated depending on the location of the deterioration or defective thyristor.
As a result, which thyristor is deteriorated or defective can be determined based on the difference in the measured current value.

[0014]

The present invention will be described in more detail by way of examples with reference to the drawings. FIG. 3 is a circuit diagram of the abnormality detecting device of the present invention, and FIG. 4 is a front view showing the outer shape of the device. The voltage of the commercial power supply 10 is transformed into a low voltage of, for example, about 10 V by the transformer 12 via the two-pole snap switch 11. The primary side 13 is a fuse, 14 is a resistor, and 15 is an indicator lamp for determining whether or not the power is turned on. On the secondary side, connection terminals 16A and 16B for applying an AC voltage after transformation to both ends of the target thyristor, and a wide range ammeter 17A for measuring a current flowing across the thyristor element, A narrow range ammeter 17B is provided in parallel, and push buttons 18A and 1 for selection are provided on the way.
8B is provided. Reference numeral 19 is a resistance, and 20 is a voltmeter for displaying the applied voltage.

In the present invention, using such a detection device, the connection terminals 16A and 16B are connected to both ends of the target thyristor element, and the current value is read while selecting the ammeters 17A and 17B. This makes it possible to determine which thyristor element is deteriorated or defective.

The measuring principle will be described below. That is,
As shown in FIG. 2, differences between the abnormal thyristor parts when the connection terminals of the detection device of the present invention are respectively connected to both ends of the thyristor element UA will now be described with reference to equivalent circuits.

A) When all thyristors are normal (FIG. 5) The equivalent circuit in this case can be expressed as (B) in FIG. 5, where the impedance in the circuit is Za and the measured current value of the device of the present invention is Letting Ia, Za and Ia are respectively expressed by the following equations.

Za = R−j · 1 / ωC Ia = ACV / Za where ACV is the applied voltage, R is the impedance of the resistor R, and ωC is the capacitive reactance of the capacitor C (ω = 2).
πf, f is the frequency of the output voltage), and j is a complex number.

B) When only the UA or XB thyristor element (or) is abnormal (FIG. 6) Zb = r × (R−j · 1 / ωC) / (r + R−j · 1 / ωC) Ib = ACV / Zb However, r represents the internal resistance of the abnormal thyristor element.

C) When only the UA or XB thyristor element (or) is abnormal (FIG. 7) Zc = 1 / [1 / r + (R−j · 1 / ωC) × 2] Ic = ACV / Zc d) VA When any of the thyristor elements (~ or ~ (12)) of ~ ZB is abnormal (Fig. 8)

[0021]

[Equation 1]

Thus, it is found that the measured current value differs depending on the abnormal portion of the thyristor element. Therefore, conversely, it is possible to check these relationships in advance and determine the abnormal portion of the thyristor element according to the measured current value.

(Experimental example) Incidentally, in the cycloconverter equipment to be tested of the present invention, C = 10 [μF], R = 4
0 [Ω], and the transformer Rt≈0 [Ω], Lt≈6
When the impedances Za to Zd of a) to d) are calculated with 6 [mH] and r = 20 [Ω], Za = 320 [Ω], Zb = 19.82 [Ω] Zc = 19.3 [Ω] ], And Zd = 29.33 [Ω].

Subsequently, the output voltage of the measuring instrument is AC10V, f
= 50HZ, current values Ia to Id of a) to d) are calculated as follows: Ia = 0.03 [A], Ib = 0.50 [A] Ic = 0.52 [A], Id = 0.34 [A], which is almost in agreement with the experimental result.

On the other hand, the time until the abnormality of the thyristor is detected and repaired by using the present invention is compared with the time until the abnormality of the thyristor which is performed without using the present invention is detected and repaired. As a result, when the present invention was not used, it took an average of 1 hour and 49 minutes, whereas when the present invention was used, it was an average of 4 hours.
The repair time was reduced to 0 minutes and 69 minutes on average, and the repair time could be greatly shortened.

[0026]

As is apparent from the above description, even in a cycloconverter having a complicated internal structure, a defective thyristor can be identified without disassembling the device, and measurement can be performed with a simple device. Can be simplified and the measurement time can be shortened, and advantages such as safe measurement without applying stress to circuit components are brought about.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a main circuit of a cycloconverter device.

FIG. 2 is an explanatory diagram of a state in which a main portion of the detection apparatus of the present invention is measuring.

FIG. 3 is a circuit diagram of the device of the present invention.

FIG. 4 is a front view showing the outer shape of the device of the present invention.

5A is an explanatory diagram of an abnormal state measurement state of a thyristor element, and FIG. 5B is an equivalent circuit diagram.

FIG. 6A is another explanatory diagram of the abnormal state measurement state of the thyristor element, and FIG. 6B is an equivalent circuit diagram.

FIG. 7A is another explanatory diagram of the abnormal state measurement state of the thyristor element, and FIG. 7B is an equivalent circuit diagram.

8A and 8B are different explanatory views for measuring an abnormal state of the thyristor element, and FIG. 8B is an equivalent circuit diagram.

[Explanation of symbols]

10 ... Commercial power supply, 12 ... Transformer, 15 ... Indicator lamp,
16A, 16B ... Connection terminals, 17A, 17B ... Ammeter,
20 ... Voltmeter, T ... Transformer, M ... Induction motor.

Claims (2)

[Claims] 1. When detecting an abnormality of a thyristor element group in a cycloconverter, an AC voltage is applied to both ends of a certain thyristor in a built-in state, a current value flowing through the both ends is measured, and impedance of a circuit including the thyristor is measured. A method for detecting an abnormality in a thyristor element, comprising detecting an abnormal thyristor element based on a difference in current value based on the difference. 2. Detecting an abnormality of a thyristor element group in a cycloconverter, which is a plug-in terminal to a commercial AC power supply, an AC voltage transformer, a voltmeter after transformation, and an AC voltage after transformation. A thyristor element abnormality detection device comprising a connection terminal for applying a voltage to both ends of the thyristor element and an ammeter for measuring a current flowing through both ends of the thyristor element, which are integrated.