JPH0599979A - Detecting apparatus of deterioration of thyristor - Google Patents

Abstract

PURPOSE:To inexpensively, easily and correctly detect the on-state of a thyristor element dependent on the temperature that has conventionally been difficult to be detected. CONSTITUTION:This apparatus is comprised of a current detector 11 which detects the current difference flowing in parallel thyristor elements, a resistance 12 which converts the current difference detected by the detector 11 to a positive or a negative voltage, a comparator 14 which outputs a 1 or -1 signal to a logic circuit 15 for judgement when the converted positive or negative voltage exceeds a predetermined absolute value, a comparator 16 which detects an alternating current voltage impressed to the thyristor and outputs a 1 or -1 signal to the logic circuit 15 depending on whether the voltage is positive or negative, and the logic circuit 15 which detects the thyristor element in the on-state based on the combination of the 1 or -1 signals input from the comparators 14 and 16. Accordingly, the thyristor element which is in the on- state can be easily detected at low costs while the element is made conductive. Even the phenomenon of the on-state dependent on the temperature can be correctly detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the presence or absence of deterioration of a thyristor element used in an AC voltage regulator or the like.

[0002]

2. Description of the Related Art An AC voltage regulator such as a high frequency welding machine is made by controlling the phase using a thyristor element and converting it to another voltage. An example of the main circuit and the current detection circuit are shown in FIGS. Generally, an AC voltage regulator often uses thyristor elements in parallel to increase the current, and has a circuit configuration that detects the maximum current in each phase. Thyristor elements used in AC voltage regulators, etc. have a bending stress in silicon due to the difference in thermal expansion of copper, silicon, etc. due to the increase in contact heat due to the decrease in the pressure contact force of the silicon wafer and the increase in the allowable junction temperature due to the heat cycle. This causes cracks in the silicon, which increases the leakage current and causes deterioration.

The deterioration of the thyristor element causes the following problems. That is, when an imbalance occurs in the current in each phase, the current detects the maximum value, so that the total current in the phase is suppressed to be lower than when the imbalance does not occur. As a result, the output of the entire device is reduced. Further, even if the thyristor element is ignited to cause an overcurrent fault, unlike the thyristor Leonard device, an AC short circuit does not cause a fuse blow, so that the cause of the fault cannot be easily determined. Among the above problems, in order to reduce the overall output, it is possible to periodically measure the thyristor current in each phase and, if there is an abnormal imbalance, take measures such as replacing the thyristor element. However, the arcing of the thyristor element occurs suddenly and cannot be easily detected.

Generally, as a method for diagnosing deterioration of a thyristor element, a thyristor element incorporated in a circuit is taken out, a variable DC power source is connected between its cathode and anode, and a DC voltage is applied to the thyristor element. Is increased sequentially, the leakage current flowing in the thyristor element at that time is measured through a resistor, and the calculated value of the applied voltage / leakage current is detected as an insulation resistance value.
In this case, in order to perform the deterioration diagnosis, it is determined that the leakage current value when the rated voltage of the thyristor is applied is within the predetermined control value, and that the leakage current value is within the predetermined control value. There is a method and a method of determining whether or not the state is normal based on the increase pattern of the leakage current with respect to the value of the applied voltage. However, in the method for diagnosing deterioration of the thyristor element, it is necessary to remove each thyristor element from the circuit in which it is incorporated,
Therefore, it is troublesome, and troubles due to misconnections are likely to occur during removal and installation, and moreover, the thyristor element may be damaged during removal of the thyristor element, or troubles such as overheating due to improper tightening during installation are likely to occur. There was a problem.

As a method for solving the above-mentioned problems of the method for diagnosing the deterioration of the thyristor element, the thyristor element connected in the circuit is kept in the connected state and made non-conductive,
A single-phase voltage is applied between both terminals of the thyristor element, and a leak current generated by the single-phase voltage is detected in a non-contact state by a current transformer, and deterioration of the thyristor element is diagnosed based on the detected current. Method (JP-A-62-80567)
No. gazette) is proposed.

[0006]

The arcing of the thyristor element depends on the temperature of the thyristor, and does not arc even if a voltage is applied at a low temperature (room temperature) such as when the apparatus is stopped,
There are many phenomena in which the temperature of the thyristor element gradually rises after the start of use of the device and an arc starts. For this reason, JP-A-62
As in the method disclosed in Japanese Unexamined Patent Publication No. -80567, a single-phase voltage is applied between both terminals in a non-conducting state, and a leak current generated by the single-phase voltage is detected by a current transformer in a non-contact state, If the deterioration is determined based on the detected current, it may be difficult to determine that the thyristor element is deteriorated, and the arcing phenomenon cannot be prevented.

Further, in the current apparatus, even if an arc occurs and an overcurrent fault occurs, the fuse is not blown. Therefore, the cause of the fault is difficult to understand, and the fault occurs for a long time, resulting in operational loss. It becomes extremely large. On the other hand, some devices always detect the thyristor gate waveform and the thyristor current, and if the current is detected before the gate waveform appears, it detects that it is an arc, but it is necessary to replace the existing device. Yes, it is not a cost-effective method.

An object of the present invention is to provide a thyristor deterioration detecting device capable of inexpensively detecting the arcing of a thyristor element, which was difficult to detect by the conventional device.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies to achieve the above object. As a result, the difference between the currents flowing in the parallel thyristor elements connected in the circuit and the AC voltage applied to the thyristor are detected, and when the detected current difference exceeds a certain absolute value, the positive and negative voltages and the AC voltage are detected. Based on the positive / negative of, it was clarified that the arc thyristor element in the circuit can be detected, and the present invention was reached.

That is, according to the present invention, in an AC voltage regulator for converting an AC voltage into another AC voltage by phase control, a current detector for detecting a difference between currents flowing in each parallel thyristor and a current detector for detecting the difference. A resistor that converts the current difference into a positive or negative voltage, and 1 or -1 when the positive or negative voltage value input from the resistor exceeds a certain absolute value.
, A comparator for outputting the signal to the decision logic circuit, a comparator for detecting the AC voltage applied to the thyristor and outputting a signal of 1 or -1 to the decision logic circuit depending on whether the thyristor is positive or negative, and each comparator. It is a deterioration detecting device for a thyristor, which comprises a judgment logic circuit for judging a thyristor that has ignited based on a signal of 1 or -1 input from.

[0011]

According to the present invention, the difference in current flowing through each parallel thyristor element is detected by the current detector, converted into a positive or negative voltage by the resistor, and then the positive or negative voltage value is detected by the comparator as an absolute value. When the current difference corresponding to 10% to 20% of the thyristor rated current is detected, a signal of 1 or -1 is output to the decision logic circuit. Further, the comparator outputs a signal of 1 or -1 to the decision logic circuit according to the positive or negative of the AC voltage of each parallel thyristor. The decision logic circuit decides which thyristor element has fired in accordance with the combination of the signal of 1 or -1 according to the current difference or the alternating voltage input from each comparator.

Therefore, according to the device of the present invention, it is possible to detect the arcing of the parallel thyristor element in the normal conducting state without bringing the thyristor device into the non-conducting state. It is possible to easily detect the arcing phenomenon of the thyristor element depending on the temperature. The device of the present invention is also effective for detecting the current imbalance of each parallel thyristor element, and the periodic inspection for determining the current imbalance can be omitted.

[0013]

EXAMPLE A parallel thyristor element U of the main circuit in an AC voltage control circuit using a thyristor device as shown in FIG.
The difference between the currents flowing through -U 'and XX' is detected by the current detector 11 of the device of the present invention shown in FIG. Then, the resistor 12 converts the current flowing in the U thyristor element into a positive voltage, for example. A filter 13 has a function of preventing a current difference due to a slight deviation of the firing timing of each thyristor element U-U ', XX' from being detected. For example, at a commercial frequency of about 1 msec. Have a constant. Reference numeral 14 is a comparator, which outputs 1 or -1 when the input positive or negative voltage value exceeds a certain absolute value.
The signal is output as a logical value to the judgment logic circuit 15. 1
Reference numeral 6 denotes a comparator which outputs a signal of 1 or -1 to the decision logic circuit 15 depending on whether the UV voltage is positive or negative. The decision logic circuit 15 determines whether the positive or negative voltage value based on the current difference input from the comparator 14 and the signal of 1 or -1 according to the positive or negative of the U-V voltage input from the comparator 16. Depending on the combination of 1 or -1 signals when a certain absolute value is exceeded, which thyristor element U, based on the criteria shown in FIG.
It is configured to determine whether U ', X, and X'have passed.

Because of the above-mentioned structure, for example, when the thyristor element U arcs, a parallel thyristor element U'is formed.
There is a current difference between and. This thyristor element U-
The current difference between U'is detected by the current detector 11 and the resistance 1
It is converted into a positive voltage by 2 and is output to the comparator 14 via the filter -13. Then, the comparator 14 sends 1 to the decision logic circuit 15 when a current difference corresponding to an input positive voltage value of 10 to 20% of the thyristor rated current is detected.
The signal of is output. On the other hand, since the UV voltage is positive, the signal of 1 is output from the comparator 16 to the decision logic circuit 15. The determination logic circuit 15 can determine from the 1 signal input from the comparator 14 and the 1 signal input from the comparator 16 that the thyristor element U has made an arc according to FIG. Although the above description has been given for the thyristor elements U and X, this circuit is referred to as a thyristor element V,
By using Y, W, or Z, it is possible to similarly determine which thyristor element has fired. In the above description, the case where the number of parallel thyristor elements is two has been described, but the case of three or more parallel thyristor elements can be determined by adding a similar circuit.

[0015]

As described above, according to the device of the present invention, it is possible to easily detect a thyristor element which is arced at low cost and to accurately determine the arcing phenomenon depending on the temperature of the thyristor element. it can. Further, the device of the present invention is
Since the current imbalance can be detected, there is also an effect that the periodical inspection for determining the current imbalance can be omitted.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an arc thyristor element detection circuit according to the present invention.

FIG. 2 is an explanatory diagram showing an example of the arc thyristor determination of the determination logic circuit in the embodiment.

FIG. 3 is a main circuit diagram of an AC voltage regulator.

FIG. 4 is a current detection circuit diagram of a main circuit of the AC voltage regulator.

[Explanation of symbols]

 11 current detector 12 resistance 13 filter 14 and 16 comparator 15 decision logic circuit

Claims (1)

[Claims] 1. In an AC voltage regulator for converting an AC voltage into another AC voltage by phase control, a current detector for detecting a current difference flowing in each parallel thyristor element and a current difference detected by the current detector. To a positive or negative voltage, a comparator for outputting a 1 or -1 signal to the decision logic circuit when the positive or negative voltage value input from the resistance exceeds a certain absolute value, and the thyristor. A comparator that detects the AC voltage applied to the comparator and outputs a 1 or -1 signal to the judgment logic circuit according to whether it is positive or negative, and an arc based on the 1 or -1 signal input from each comparator. A deterioration detecting device for a thyristor comprising a judgment logic circuit for judging a thyristor element.