JPH0253106B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormality processing device for an electrostatic precipitator, which is mainly used for environmental improvement, and the distance between the collecting electrode plates does not exceed 10 mm. This type of electrostatic precipitator generally has the possibility of heating the collected material due to abnormal sparks or high-resistance short circuits caused by solid foreign matter attached between the electrode plates. Appropriate preventive maintenance measures are required when handling flammable materials.

A method as shown in FIG. 1 is conventionally known as this type of preventive maintenance measure. This figure shows an example of a two-stage electrostatic precipitator in which the charging section and the dust collection section are electrically separated. In FIG. 1, reference numeral 1 denotes a step-up transformer, which outputs a high voltage necessary for dust collection by inputting a commercial line power supply voltage. This output is rectified by a rectifier unit _D1 to supply a high DC voltage to the corona discharge section, that is, the charging section 4 and the dust collection section 5 of the electrostatic precipitator. On the other hand, the opposite pole sides of these DC high voltages are coupled to path 7 via path 8 and path 9, and path 7 is connected to envelope 6 of the electrostatic precipitator and grounded here. With such a configuration, the current flowing through the charging section 4 and the dust collecting section 5 of the electrostatic precipitator main body becomes equal to the current flowing through the path 8 and the path 9, respectively. Therefore, as a means of detecting the current flowing through the charging section 4 and the dust collection section 5, the current value is converted into a voltage value by inserting resistors 10 and 11 into the circuit from path 8 and path 9 to path 7, respectively. , these voltage values are sent to the comparator 12
and 13 are compared with predetermined thresholds −v ₂ and −v ₁ , respectively, and if any of the absolute values of the voltages exceeds the absolute value of these thresholds, the output of each comparator causes transistor 1 to be
4 is activated, the relay 15 is activated, and the switch 16 of the main converter input circuit is released, thereby stopping the supply of high voltage to the electrostatic precipitator main body. Or to prevent fire accidents in the dust collection area.

However, this method has the following drawbacks.

In the electrostatic precipitator that is the subject of the present invention, where the spacing between the electrode plates is relatively small, electrical phenomena such as sparks that occur unavoidably and are not dangerous unless the frequency is too large, and the gap between the electrode plates. Since electrical phenomena such as short circuits that immediately lead to the risk of fire may occur, it is essentially impossible to judge the degree of danger simply by the magnitude of the current value.
and 11 are connected in parallel. These capacitors serve as a preventive maintenance circuit by absorbing the electrical energy that flows out through path 7 due to sparks and by absorbing the short circuit current for a certain period of time to create a delay between the occurrence of the short circuit current and the operation of the comparator. It is said that it is possible to prevent malfunctions. However, in order to increase the abnormal current detection sensitivity in this circuit configuration, for example, if the value of the resistor 11 is increased,
In order to keep the delay time unchanged, the capacitance of the capacitor 18 must be reduced, and if the capacitance of the capacitor 18 is reduced, the capacitor will be charged to the set voltage value with a smaller amount of charge, resulting in malfunction due to the generation of sparks. Resistance is reduced. Conversely, if the capacitance of the capacitor is not reduced in order to prevent the spark malfunction resistance from decreasing, the delay time will become too short and malfunction will occur, resulting in contradictory requirements for the capacitor's capacity.
Therefore, it has the disadvantage that malfunctions often occur in practical devices.

The object of the present invention is to eliminate the above-mentioned drawbacks and provide an electrostatic precipitator that is safer and less likely to malfunction.

FIG. 2 shows an embodiment of the present invention, and the configuration of the transformer 1, rectifier unit, charging section 4, dust collection section 5, envelope 6, paths 7, 8, and 9 is the same as in FIG. 1. It is. In this embodiment, a photocoupler 20 is inserted between paths 7 and 8, and a photocoupler 21 is inserted between paths 7 and 9. The emitters of the output transistors of the photocoupler are grounded via resistors 22 and 35, and the anti-ground ends of each resistor are connected to comparators 23 and 2, respectively.
4 and comparators 25 and 26. The output terminals of the comparators 23, 24, 25, and 26 are all connected to one of the input terminals of the microcomputer 27 on a one-to-one basis.

One of the output terminals of the microcomputer 27 is connected to the transistor 3 via a buffer inverter 28.
0, and the collector of the transistor 30 is connected to a DC power supply via a relay 32. The other one of the output terminals of the microcomputer 27 is connected to the base of the transistor 31 via the buffer inverter 29.
The collector is solid state photo relay 33
It is connected to a DC power supply via a trigger diode 33a. Next, the operating principle of this circuit configuration will be explained.

In this embodiment, photocouplers 20 and 21 are used as a means for detecting the current flowing through the charged part and the dust collecting part of the electrostatic precipitator, and the input current of these photocouplers is almost the same as the current flowing through the charged part and the dust collecting part of the electrostatic precipitator. corresponds to the current flowing through the part. Since the output current value of the photocoupler increases monotonically as the input current value increases, the emitter terminal voltage of the photocoupler 20 and 21 will eventually increase with respect to the increase in the current in the charged part and the dust collecting part of the electrostatic precipitator body. , initially increases in a monotonically increasing manner, and changes as follows when it is saturated at the value of the supplied DC voltage V+.

The current value flowing through the charging part and the dust collection part of the electrostatic precipitator main body has a range of appropriate values designed in advance, and the emitter terminal voltage of the photocouplers 20 and 21 corresponding to these upper and lower limits is lower than zero. It is easy to set the values of the resistors 22 and 35 so that the voltage is large and smaller than the saturation voltage. With this setting, it is easy to determine whether or not a current abnormality has occurred in the electrostatic precipitator by detecting the output states of the comparators 23, 24, 25, and 26. Now, the problem is when a current abnormality occurs in an electrostatic precipitator, it is necessary to accurately judge whether it is an abnormality that poses a risk of fire or the like, or whether it is an abnormality that should be tolerated as a mere transient electrical phenomenon.

In this respect, the present method has a distinctive feature.
According to the inventor's experiments, abnormalities that pose a danger such as ignition are, for example, when oil-based cutting oil and fiber dust are mixed on the dust collecting electrode plate and the frequency of spark generation exceeds a certain limit, and when the dust collecting electrode plate This is a case where a half-short circuit state caused by a foreign object between the two terminals occurs. Of these, the former is a known danger, but the latter is a danger that has become clear as a result of the inventor's various experiments, and based on the results, the inventor has determined that It was concluded that the current control of several milliamperes is insufficient, and that the detection sensitivity needs to be increased by at least an order of magnitude.
This purpose can be achieved by setting the value of resistor 35 to several tens of kilohms. On the other hand, when a spark occurs, the instantaneous value of the current may reach several kiloamperes, but this current does not flow directly into the photocoupler, but is temporarily stored in the capacitor 18 and then passed through the photocoupler 21 and resistor 36. is discharged. At this time, the resistor 36 is the photocoupler 2
1 serves as a protective resistor. Considering only the purpose of protecting the photocoupler, the higher the value of this resistor, the better; however, on the other hand, the short-circuit current that may occur when the dust collector plate is completely short-circuited (a protective resistor is generally installed in the main electric circuit of the dust collector, but the impedance There is a limit to this resistance value in order to prevent voltage drop, and it is usually unavoidable that several milliamps flow through the resistor 36.
The resistance value must be small enough to prevent high voltage from occurring across the terminal. For this reason, the value of the current flowing through the photocoupler input side when a spark occurs is usually larger than the detection limit for the aforementioned half-short circuit state. Therefore, the emitter terminal voltage of the photocoupler 21 reaches the saturation voltage every time a spark occurs. Therefore, the microcomputer 27 temporarily determines this to be abnormal, but this state is canceled almost at the same time as the spark ends, and the time required for this is less than 1 ms. On the other hand, if a half-short circuit occurs and continues, the output state of the comparator is the same as the former, but it continues for more than 1 ms, and it is possible that sparks were generated between the dust collecting plates due to the difference in time. It is possible to clearly determine whether the device is in a semi-short circuit state. Furthermore, by using the timer function and memory function built into the microcomputer, the frequency of spark occurrence can be quantitatively detected, and if the spark frequency exceeds a dangerous limit, this can also be clearly determined.

If the microcomputer recognizes the occurrence of a half-short circuit or excessive spark frequency, it will automatically shut down the power and display a maintenance request, but these dangerous conditions can be recovered by simply removing the voltage. To prepare for such a situation, turn off the power using the solid state photo relay 33, let the device rest, then turn it on again, and only if the situation does not recover, turn off the relay 32. The self-hold of the relay 34 is released, the device is stopped, and a maintenance request is displayed.

Next, the operation of the microcomputer 27 in the embodiment of the present invention will be explained based on the general flowchart shown in FIG. S1 to S33 indicate steps, starting at step S1,
After the necessary initialization is performed in step S2, the transistor 31 is made conductive via the buffer inverter 29 in order to turn on the solid state photorelay (SSR) 33 shown in FIG. 2 in step S3. Solid state photo relay (SSR) 3
3 is a well-known one, and is turned ON when a voltage is applied to the trigger diode 33a, and turned OFF when the voltage is applied to the trigger diode 33a. Next, in step S4, a predetermined time period (100 ms in the embodiment) is set, and then, in step S5, a check is made to see if there is an abnormality in the current. Specifically, the outputs of the comparators 23 to 26 shown in FIG. 2 are checked at the same time. If there is no abnormality, this step S5 is repeated, but if there is an abnormality, check which comparator outputs it. First, in step S6, there is insufficient current in the dust collection section (there is an output from the comparator 26),
In step S7, excessive current in the dust collection section (with output from comparator 25) is checked.

If there is insufficient current in the dust collecting section, the process jumps to step S23, the signal is taken in again, and the presence or absence of outputs from the comparators 23 to 26 is checked in step S24. If there is no abnormality, the process returns to step S5. If there is an abnormality, "1" is subtracted from the register that is preset with the number of scheduled abnormality detections, and if it is not zero, the step is executed.
Return to S5. If it is zero, it is assumed that the number of abnormalities detected has reached a predetermined number, and the solid state photorelay (SSR) 33 is turned off in step S26, and after a predetermined period of time (1 second in the embodiment) is set in step S27, the process returns to step S28. Turn on SSR33 with .
A predetermined time (100 msec in the example) in step S29
After holding it, check whether the current abnormality still occurs in step 30. If no abnormality occurs, proceed to step
Return to S5, and if the abnormality still occurs, stop the device in step S32 (power off by relay 32), sound the buzzer, etc., and proceed to step S33.
It ends with.

If the current in the dust collection section is excessive, the step
Proceeding from S7 to step S8, if the excess condition is e.g.
Check to see if it continues for more than 20msec. If it continues, it is assumed that a short circuit has occurred and a solid state photo relay (SSR) is activated.
Turn 33 off. The subsequent steps S10 to S13 have the same concept as the above-mentioned steps S27 to S30, and are aimed at recovery by temporarily turning off the power. If the excessive current condition disappears in step S13, the process returns to step S5, but if it does not disappear, the process returns to step S32.
Jump to stop the device.

If the excessive current condition is a short-lived one (spark) of 20 msec or less in step S8, the spark frequency is checked based on a standard of, for example, about 5 times/second in step S14, and if the frequency is excessive, the device is stopped. , if the frequency is low, it is considered normal and returns to step S5.

If the current in the collecting part is neither insufficient nor excessive, there is an abnormality in the charging part, but if the current in the charging part is insufficient (step S15) or if there is no excess or deficiency in the current (an error in step S5 or a very short period of time). (in the case of current abnormality), the process jumps to step S23.

If it is determined in step S16 that the current in the charged part is excessive, in step S17 the excessive state is determined to be 20 m, for example.
It is checked to see if it continues for more than sec, and if it continues, it is assumed that a short circuit has occurred and the process proceeds to steps S18 to S21 (same subroutine as S26 to S29 and S9 to S12), and the recovery state after the power is turned off and then turned on again is checked. If it is determined in step S22 that recovery has occurred, the process returns to step S5, and if it is determined that the current is still excessive, the apparatus is stopped.

If the duration of the excess current in the charged section is 20 msec or less, the process jumps from step S17 to step S31 to check the spark frequency, and if the frequency is excessive, the device is stopped, and if the frequency is low, the process returns to step S5.

As can be seen from the above description, in the present invention, a photocoupler is inserted into the electric circuit of the dust collection part in an electrostatic precipitator, the output current of the photocoupler is converted into a voltage using a resistor, and this voltage is guided to a comparator. The structure distinguishes between sparks and short-circuit or semi-short-circuit conditions based on the characteristics of temporal changes in the output level of the comparator, and in the case of sparks, quantitatively recognizes the frequency of occurrence, which poses a risk of ignition. It is now possible to clearly identify whether short-circuit or semi-short-circuit conditions or excessive sparks have occurred, or whether there has been a single spark that is merely a transient and non-hazardous electrical phenomenon; It is also possible to increase the detection sensitivity of half-short circuit current. Therefore, due to these comprehensive effects, it is possible to realize electrostatic precipitator control that is much safer than the conventional method and has fewer malfunctions.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the conventional method, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is an example of a general flowchart of the embodiment of the present invention. 4: Charge section, 5: Dust collection section, 20, 21: Photo coupler, 23 to 26: Comparator, 27: Microcomputer, 33: Solid state photo relay (SSR).

Claims (1)

[Claims] 1. A photocoupler that detects the charged part of the electrostatic precipitator or the current of the precipitator and generates an output current;
means for converting the output current into voltage; comparison means for comparing the output voltage of the means with a set voltage; and determining the presence or absence of an output from the comparison means and the duration of the output, and determining that the duration of the output is predetermined. a microcomputer as a discriminating means for discriminating the occurrence frequency of the output when the output is less than the above value; 1. An abnormality processing device for an electrostatic precipitator, comprising means for permanently cutting off power to the electrostatic precipitator based on the determination result of a microcomputer.