JPS5981919A - Method and device for protecting thyristor of pulse generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and a device for protecting switching elements of a pulse generator from overloading due to spark overs occurring in an electrostatic precipitator.

It has been demonstrated that the efficiency of known two-electrode precipitators can be improved by superimposing high voltage pulses of appropriate duration and repetition rate on the operating DC voltage. The initial pulsing action is reliable enough to transfer the significant amount of charge required to charge the capacitance of the precipitator to the required high constant 1 mopulse level many times per second. This was hampered by the lack of high-constant isolation elements. This problem was solved by using Cyrisk for the switch element.

However, if a spark occurs while the thyristor is in the on-state, the thyristor experiences a spark-over current whose peak value can exceed 5 to 10 times the normal on-state current. Generally, a thyristor can withstand temporary overloads of such short duration, but if the short-term overloads occur at very small intervals, the overload will cause the temperature to rise and the thyristor will fail. It turns out.

According to the present invention, in order to protect the thyristor by controlling the incidence of spark overs in the precipitator, the number of spark overs and the number of spark overs and the predetermined number of spark overs after the first spark over Start measuring the difference between the number of times the cooling period has elapsed, and the difference is O
The measurement is stopped when the next spark over occurs, and the measurement is restarted when the next spark over occurs, and when the difference exceeds a predetermined number, the measurement is performed to reduce the possibility of further spark overs occurring. controlling one or more relevant operating parameters of the duster;

A series of numerical values are defined for the difference values, each numerical value corresponding to a different effect that exerts a modification on the operating parameter. The effect on the operating parameters of the precipitator is numerically dependent; the higher the value the less spark over occurs.

The present invention utilizes a spark over incidence control system with a well-known pulse detector and spark over detector to detect pulse and spark over occurrences by measuring changes in precipitator voltage or pulse current. To detect.

Spark over occurrence rate control is accomplished by means of generating a control voltage that increases by one step voltage each time a spark over occurs and decreases linearly over time at a rate corresponding to the required or desired cooling period. ,1
A signal is provided that triggers control over the operating parameters of the precipitator when the control voltage exceeds a predetermined level or one of a number of predetermined levels.

The action taken when the first level is exceeded is to temporarily reduce the height of the pulse (eg by 10%). After this temporary reduction, the pulse height is increased to its previous magnitude or to a level controlled by a pulse height controller as described in UK Patent Application No. 0054878.

Beyond the second level, the reduction in pulse height is twice as high (20%) as at the first level, after which the pulse is returned to its original or adjusted level.

Above the third level, the trigger signal to the thyristor of the pulse circuit is blocked at the reed where the control signal falls below this eighth level.

When the fourth level is exceeded, the control voltage drops below the fourth level, and not only the pulse but also the circuit case that sends out the DC voltage on which the pulse is superimposed is stopped, and the trigger signal to the thyristor is stopped. becomes 1 inch blocked by a trench where the control signal drops below the third level.

The spark rate control device described above can also be used to control the spark rate in a conventional electrostatic precipitator powered by a simple DC voltage. In such a precipitator, the DC voltage rises slowly until spark over occurs, at which point the voltage immediately drops by a certain value and then rises slowly again.

The rate at which it increases and the value at which the voltage decreases can be made dependent on the number of sparks and the time interval at which the spark over occurs by means of the above-mentioned snow overflow rate control device.

The present invention will be explained in detail below according to examples.

In FIG. 1, normally the spark over control voltage VC
is 0. However, spark over occurs when the precipitator is being pulsed at time TI. This initiates the observation of the difference between the number of pulses (including the first pulse) and the number of passages of a certain cooling period. For observation, increase the control voltage by one step voltage V8 -Vs/1
This is done by linearly decreasing the temperature at a rate of k (tk is a predetermined cooling period). If no spark over occurs again before the cooling period has elapsed, the control voltage becomes 0, the aforementioned difference becomes 0, and the measurement of the difference starts from the beginning when the next new spark over occurs. Ru.

It is shown that another observation begins at time T2.

Before the cooling period has elapsed, a new spark over occurs at time T3, which causes the control voltage to increase in steps KEVs
only rises. After the cooling period from the previous spark over (Ta), further spark over occurs (T4
), a new step voltage Vs is added to the control voltage before the difference between the number of spark oats and the number of cooling periods becomes zero, and the observation does not end. The observation ends when the control voltage becomes 0 at time T, that is, when the difference becomes 0.

At time T6, a spark occurs during pulse generation and a new measurement sequence begins. As shown, a series of spark overs causes the control voltage to rise stepwise until time T
At level 7, it exceeds level "α". This indicates that precautions must be taken to reduce the possibility of further spark over during pulsing.

The preventive measure is to reduce the pulse voltage (for example by 10 cm). After being adjusted to be lower,
The pulse voltage is increased to a predetermined value or to a value regulated by an automatic control device.

Despite this adjustment, it is shown that a new spark over occurred at time r"8. This new spark over caused the control voltage to rise to level "b".
” will be exceeded. This indicates that more powerful preventive measures are required than when level "α" is exceeded. The means for this is, for example, to reduce the pulse voltage by 20%. The pulse voltage is returned to the initial setting value or adjusted value again.

In the example shown here, even with this second precaution, spark over occurs and the control voltage increases by Vs;
Although it decreases at a constant rate with a slope determined by a predetermined cooling period, the control voltage exceeds level "C" at time Tg. This indicates that more stringent precautionary measures are required, 5 for example to stop the pulse by blocking all trigger signals to the thyristor controlling the pulse.

As a result, spark over is prevented at time Tlo, the control voltage is lowered below the level r6J that instructs the blocking of the trigger signal to the thyristor, and the preventive measure is cancelled.

However, at time T, 1, blocking of the trigger signal becomes necessary, and although the trigger signal is blocked, spark over occurs due to a noise signal or other reasons and furthermore, the level rdJ is reached at time It exceeds at T1□. This emergency preventive measure can, for example, stop the regulator for the DC voltage and completely terminate the spark over. When the control voltage falls below level "d" at time T13, the emergency preventive measure is canceled, but the stoppage of the trigger signal to the thyristor is maintained until the control voltage falls below level "c" at time T14.

As shown, the control voltage continues to decrease after passing level "c". Nothing happens even if the control voltage exceeds level "b" from above, but at time T1. If a spark over occurs and the level "b" is exceeded from below, preventive measures corresponding to the level "b" (reducing the pulse voltage by a factor of 20) are taken.

FIG. 2 is a block diagram of an apparatus used in the method described above in connection with an electrostatic precipitator energized by pulses superimposed on a high DC voltage. The precipitator power supply has a control unit that provides high DC voltage and pulsed voltage, and a thyristor that performs pulse switching. Additionally, a spark over detector is provided.

The spark rate control device receives a signal from the spark over detector via line 9 when a spark over occurs. This signal is converted into a pulse of a predetermined width by the device 1 and sent to the line 10. This signal is fed to a device 2 which integrates the signal generating the step voltage to generate an output signal, where the built-in fixed integration reduces the output voltage by -Vs/lk. Integration stops when the output 1 word on line 11 reaches 0.

In device 3.4.5.6 the voltage on line 11 is compared with the set voltages corresponding to said levels "a", "b", "C" and "d". The radial specific force signals from devices 3 to 6 throttle the precipitator power supply unit as described above. For example, the DC power supply of the precipitator is turned on and off when a signal is present on line d. Similarly, the triggering of the thyristor is blocked when a signal appears on line C.

Precautions taken when levels "c" and "d" are exceeded remain in place while the levels are exceeded;
Preventive measures when exceeding a,'' or [J are taken each time the level is passed from below. The signal that controls the pulse voltage unit to temporarily reduce the pulse voltage can be obtained by triggering each one-shot multivibrator with a lfJ force signal on lines α and b to provide a signal pulse. The one-shot multivibrators are designated 7 and 8.

As mentioned above, there are two types of preventive measures. One is temporary, in which the precautionary measure is taken temporarily and removed as soon as the control voltage falls below the level that initiated the measure. The other one is long-term, which is taken when the control yv pressure exceeds the trigger level and is not released even if the control voltage falls below the trigger level.

The number of levels and types of preventive measures mentioned above do not limit the invention. The number of levels selected for the types of preventive measures to be taken for different levels can be higher or lower as appropriate to the situation.

[Brief explanation of drawings]

FIG. 1 shows the spark over control voltage as a function of time. FIG. 2 is a block diagram of the control device. Patent Applicant: F.L. Smith & Kanno°
Ni Ni Nis (4 others) Procedural amendment (method) Showa f! December 7, 2015 Kazuo Wakasugi, Commissioner of the Japan Patent Office, Ministry of Health, Labor and Welfare (E)
-Relationship with the Nanako'n'e and βψ' cases Applicant's address % Ura, Air fl-shi, Sumitomo Ann/"47>Ha0neeeeee ≦S4, Agent

Claims (1)

[Scope of Claims] (1) In a method for protecting a thyristor switch of a pulse generator from overload due to spark over occurring in an electrostatic precipitator, the initial no spark over is equal to the spark over number and the first spark.・Start measuring the difference between the number of times a predetermined cooling period has elapsed after the overflow, and when the difference becomes zero, the a! IJ constant is stopped and restarted when the fifth spark over occurs, and when the difference exceeds a predetermined number,
One or more relevant operating parameters of the precipitator are controlled. A method characterized in that the possibility of further spark over is reduced. (2. In the method according to claim 1, a series of numerical values are established for the reference value, each numerical value corresponding to a different or modified effect on the operating parameter of the precipitator. A method in which the effect varies depending on the numerical value, and a higher numerical value corresponds to an effect in which spark over is less likely to occur. (3) In the method according to claim 1 or 2, the parameter to be controlled is One of them is the height of the pulse. (4) A method according to any one of claims 1 to 3, in which the controllable parameter is the superposition of pulses. (5) Claims The method according to any one of Items 1 to 4, wherein the parameter to be controlled is a DC voltage.・A spark generation rate control device that protects the switch, with a pulse that supplies a control voltage that increases by a step voltage every time a spark over occurs and decreases linearly over time at a rate corresponding to a predetermined cooling period. a detector and a pulse-over detector and a signal that triggers control over one or more operating parameters of the precipitator when the control voltage thereof exceeds a predetermined level or one of a plurality of levels; A device (7) comprising: a control device according to claim 6;
Apparatus for temporarily reducing the height of the pulse by a predetermined amount or percentage when the control voltage exceeds a first level. (8) In the control device according to claim 7,
Apparatus for further reducing the pulse height by a predetermined amount or percentage when the side voltage exceeds a second level. (9) A control device according to any one of claims 6 to 8, in which the trigger signal for the pulse circuit's sirisk is blocked while the control voltage is higher than the third level. (10)! 10. A control device according to any one of claims 6 to 9, in which DC voltage is blocked from being sent to the circuit while the control voltage is higher than the fourth level.