JPS58119773A - Misfire detector for thyristor converter - Google Patents

Abstract

PURPOSE:To detect the misfire of a thyristor converter with high reliability by providing a filter which cuts off the main component of a midpoint voltage waveform at the normal firing time of the converter between the positive electrode and the negative electrode of the converter and detecting the misfire based on the output of the filter. CONSTITUTION:The armature 1 of an AC generator is connected through an exiciting transformer 3 to a thyristor converter 4 of 3-phase pure bridge, and a thyristor 4a is controlled by a firing pulse unit 6, thereby controlling the current of the field coil 2. A fundamental wave is passed between the positive electrode and the negative electrode of the converter 4, a filter 10 which has characteristics for cutting off the tertiary harmonic wave, and a field ground relay 112 in a unit 11 is operated in response to the output. Accordingly, the misfire due to the malfunction of the thyristor or a gate pulse failure can be detected with high reliability by utilizing the fact that, when one phase is misfired, the main waveform component of a midpoint voltage varies from tertiary harmonic wave to fundamental wave.

Description

[Detailed Description of the Invention] The present invention relates to a misfire detection device for a thyristor converter. As a method for detecting misfire of a thyristor, conventional methods include (a) a method of substituting gate pulse loss detection; A current transformer is installed on the AC and DC sides of the thyristor converter, and a ratio tilting protection relay is used to detect converter internal failures such as commutation failure and DC short circuit. There were methods such as installing advanced equipment to judge the situation. FIG. 1 shows an example of a thyristor conversion device implementing method 0) above. In the figure, 1 is the armature of the alternator, 2 is the field coil, 3 is the excitation transformer, 4 is the three-phase pure bridge thyristor converter, 4α is the thyristor, 5 is the field breaker, and 6 is the dot. Arc pulse unit, 1 is a pulse amplifier, 8 is a gate pulse loss detection device, and 9 is a field grounding relay. With this method, even the gate pulse is lost! Can it be detected? Abnormalities in the thyristor or signal line beyond this point cannot be detected, and are treated as internal failures. With the method [batch detection ←], it may not be possible to detect only the failure of the negative thyristor, or it may be that the thyristor has failed. The current method has the disadvantage of being complicated and expensive.

This invention was made in order to eliminate the above-mentioned conventional drawbacks, and since the main component of the midpoint potential waveform of a three-phase pure bridge thyristor converter differs between normal firing and misfire, By inserting a filter that cuts off the main component t during normal ignition between the positive and negative electrodes of the thyristor converter, and detecting the output of the filter with a device that responds to this, thyristor abnormalities and loss of gate pulses can be prevented. An object of the present invention is to provide a loss-of-arc detection device for a thyristor converter that is highly reliable, has a simple configuration, and is inexpensive. Before going into the explanation of this invention, first, we will explain the waveform VGZ diagram of each part during normal firing operation of a three-phase full-wave pure bridge thyristor converter. A diagram showing the ignition sequence. The figure shows the midpoint potential waveform, and the figure C shows the rectified output waveform. As is clear from the figure, the waveform of the midpoint potential is the third harmonic of the input frequency, that is, the trademark frequency in this case.

The waveforms of this midpoint potential are the firing sequence and the rectified output waveform when the -phase thyristor goes out of firing, respectively.

The waveform of this midpoint potential is mainly composed of the fundamental wave component of the commercial frequency. As described above, when the -phase is lost, the main waveform component of the midpoint potential waveform changes from the third harmonic to the fundamental wave. FIG. 4 shows an embodiment of the present invention.

In FIG. 4, 10 is a filter inserted between the positive terminal and the negative terminal 0 on the DC side of the three-phase pure bridge thyristor converter 4. 11 is a device that responds to the filter output. As shown in FIG. 5, the filter 10 has a characteristic of passing the above-mentioned fundamental wave and inputting it into the device 11, and blocking the above-mentioned third harmonic. It is equipped with a voltage divider 2111 and a relay 112v. × is a normally closed contact of the relay. Since the field grounding relay 9 in Fig. 1 also responds to the neutral point potential, if a filter 10t is provided before the field grounding relay 9, the field grounding relay 9 9, it is possible to detect arc loss, and it is also possible to cut off unnecessary signals of the field grounding relay due to the third harmonic.

As described above, according to the present invention, a filter is inserted between the positive and negative electrodes of a three-phase pure bridge thyristor converter to cut off the main component t of the midpoint potential waveform during normal firing. It does not output when it is arcing, but it outputs when it misfires, and this filter output is detected by a device that responds to this.Since the misfiring is reliably detected on the output side of the thyristor converter, it is possible to detect thyristor abnormalities and It is possible to detect loss of arc due to loss of gate pulse with high reliability, and it can be manufactured at low cost with a simple configuration.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram for explaining the conventional method for detecting a loss of arc in a thyristor converter, and Figures 2 and 3 are diagrams showing normal firing and failure of a three-phase full-wave bridge thyristor converter, respectively. Fig. 4 is a circuit diagram of an embodiment of the thyristor converter misfire detection device of the present invention, and Fig. 5 is a characteristic diagram of the filter in the above embodiment. In the figure, %10...filter, 11...device that responds to the filter output. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent: Shin Kuzuno -

Claims (2)

[Claims] (1) A filter inserted between the positive and negative electrodes of a three-phase pure bridge thyristor converter, and 7. A mis-ignition detection device for a thyristor converter, comprising a device that responds to the filter output, and wherein the filter cuts off the main component t of a midpoint potential waveform during normal firing of the thyristor converter. (2) A field grounding relay provided in a device or a synchronous machine that responds to a filter output, and a filter is inserted before the field grounding relay, Claim 1 A mis-arc detection device for a thyristor converter as described in .