JPH0891808A - Ozonizer abnormality detection circuit - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an abnormality detection circuit for an ozonizer that can reliably detect an abnormality (arc discharge) in a cell of the ozonizer. [Arrangement] When an arc discharge is generated in the cell 6 of the ozone generator, the output voltage of the power supply unit 11 is greatly reduced even if there is no failure of commutation of the thyristor of the power supply unit 11. According to the present invention, the voltage drop is detected to detect an abnormality in the ozone generating portion of the ozonizer. That is, the comparison circuits 14a, 1
After the output voltage of the power supply unit 11 is inverted, 4b compares the output voltage of the waveform shaping circuit 13 within the first predetermined time with the reference voltage ± Vr to detect an abnormality. Further, the comparison circuit 14c compares the output voltage of the waveform shaping circuit 13 after the lapse of the second predetermined time after the output voltage of the power supply unit 11 is inverted,
An abnormality is detected by comparing with the reference voltage ± Vr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ozonizer for generating ozone, and more particularly to an abnormality detecting circuit for detecting an abnormality in an ozone generating section.

[0002]

2. Description of the Related Art In recent years, the need for pollution control and environmental protection has been emphasized, and the standards for environmental protection have become strict in the processes of sterilization and bleaching. Therefore, in this sterilization process or a bleaching process, it is a substance normally present in nature, ozone having a strong oxidizing power (O ₃₎ now is used. An example of an apparatus that is most suitable for producing ozone on an industrial scale is an ozonizer that uses silent discharge (low temperature discharge). In this ozonizer, a dielectric is attached to one discharge surface of a pair of plate-shaped discharge electrodes, and high-frequency high-voltage power is applied between the electrodes. As a result, an infinite number of minute discharges are generated between both electrodes via the dielectric. When oxygen (O ₂ ) which is a raw material gas is passed through the discharge field, it is decomposed to generate ozone.

FIG. 3 is a schematic configuration diagram showing a configuration example of an ozonizer. In this figure, reference numeral 1 is a thyristor rectifier circuit for rectifying a three-phase AC voltage, 2 is a choke coil, and a DC power supply 7 is constituted by these. 3-
Reference numerals 1 to 3-4 are bridge-connected thyristors, and 4 is a control circuit unit for driving the gates G1 to G4 of the thyristors 3-1 to 3-4. With these, the output voltage of the DC power supply 7 is changed to a high frequency AC voltage. An inverter for conversion is configured.
5-1 to 5-n are fuses, 6-1 to 6-n are cells with silent discharge electrodes, and these constitute an ozone generating portion.

Each of the cells 6-1 to 6-n is equivalent to the capacitance in terms of its structure, so that when a current flows in, the voltage V between both electrodes is increased as shown from point A to point B in FIG.
R increases sequentially. At this time, when arc discharge (high temperature discharge) occurs in the cells 6-1 to 6-n, the discharge temperature rises and ozone is not generated. Therefore, the current flowing in the cells 6-1 to 6-n is set to a high frequency current to suppress the rise of the discharge voltage. Now, when an abnormality (for example, a dielectric defect) occurs in any of the cells 6, the cell 6 shifts from silent discharge to arc discharge with a relatively low discharge voltage. As described above, each cell 6 cannot generate ozone when the arc discharge is started. When each cell 6 shifts from silent discharge to arc discharge, a large current flows through the cell 6. As a result, the fuse 5 is blown, and the thyristors 3-1 to 3-4 fail to commutate, so that the AC voltage cannot be output. Symbol E in FIG. 5 indicates the time when the commutation failure occurs.

[0005]

As described above, in the conventional ozonizer, the blowout of the fuse corresponds to the commutation failure of the thyristor. Therefore, the number of defective cells can be determined by counting the number of commutation failures. It was possible to manage. However, in recent years, a larger amount of ozone generation capacity has been required, so that it is necessary to use more cells 6 connected in parallel. Therefore, a phenomenon occurred in which one cell 6 transitioned from silent discharge to arc discharge and the commutation failure of the thyristor did not occur even though the corresponding fuse 5 was blown. FIG. 6 is a diagram showing the change in the voltage VR across the cell 6 in this case, and the time point indicated by the symbol F in this figure is the time point when arc discharge occurs. The reason why this commutation failure does not occur is that each cell 6 is equivalently a capacitance as described above,
By increasing the number of cells 6 connected in parallel, the accumulated charges increased. Therefore, even if an arc discharge occurs in one cell 6, the electric charge stored in the other cell 6 is large, and the thyristor can be commutated by the electric charge.

The present invention has been made under such a background, and when an abnormality occurs in any cell of the ozonizer, the abnormality detection of the ozonizer can be surely detected. It is intended to provide a circuit.

[0007]

According to the first aspect of the present invention,
In an ozonizer including a power supply unit that generates a high-frequency voltage and an ozone generation unit to which an output voltage of the power supply unit is applied, a voltage detection unit that detects the output voltage of the power supply unit, and an output voltage of the power supply unit, After the inversion, a first comparison means for comparing the detection voltage of the voltage detection means with a reference voltage within a first predetermined time is provided, and the ozone generation is performed based on the output of the first comparison means. This is an abnormality detecting circuit for an ozonizer, which is characterized by detecting an abnormality in a part.

According to a second aspect of the present invention, in an ozonizer including a power supply section for generating a high frequency voltage and an ozone generation section to which the output voltage of the power supply section is applied, a voltage for detecting the output voltage of the power supply section. Output voltage of the power supply section; first comparing means for comparing the detection voltage of the voltage detection means with a reference voltage within a first predetermined time after the output voltage of the power supply section is inverted. The second after is reversed
A second comparing means for comparing the detected voltage of the voltage detecting means after a lapse of a predetermined time with a reference voltage,
An abnormality detecting circuit for an ozonizer, which detects an abnormality in the ozone generator based on outputs from the first and second comparing means. The invention described in claim 3 is claim 1
Alternatively, in the abnormality detecting circuit of the ozonizer according to claim 2, the power supply section has a DC-AC conversion section by a thyristor, and the first or second comparison means sets a predetermined time from a commutation time of the thyristor. Characterized by timing.

[0009]

When the arc discharge is generated in the cell of the ozone generating section, the output voltage of the power source section is greatly reduced even if the commutation failure of the thyristor does not occur. According to the present invention, the voltage drop is detected to detect an abnormality in the ozone generating portion of the ozonizer. That is, in the first aspect of the present invention, after the output voltage of the power supply unit is inverted, the detected voltage of the voltage detection means within the first predetermined time is compared with the reference voltage to detect the abnormality. Further, in the invention described in claim 2, in addition to the invention described in claim 1, further, a detection voltage of the voltage detection means after a second predetermined time has elapsed after the output voltage of the power supply section is inverted, Abnormality is detected by comparing with the reference voltage.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. A. Configuration FIG. 1 is a block diagram showing the configuration of an ozonizer according to an embodiment of the present invention, in which parts corresponding to the respective parts in FIG. In FIG. 1, 11 is the DC power supply 7, choke coil 2, thyristor 3-1 in FIG.
3-4, which is a power supply unit configured in the same manner as the control circuit unit 4, and has a high-frequency AC voltage VR (frequency: 2 KH
z) is output. Further, the power supply unit 11 outputs the pulse signal P at the timing when the thyristors 3-1 to 3-4 commutate, and when the thyristors 3-1 and 3-4 are turned on, "H (high)". When the thyristors 3-2 and 3-3 are turned on, the signal S which becomes "L (low)" is output.

Next, the abnormality detection circuit will be described. Reference numeral 12 is a transformer, which lowers the output voltage VR of the power supply unit 11 and outputs it. Reference numeral 13 is a waveform shaping circuit composed of a filter circuit such as CR. 14a to 14c are
Each is a comparison circuit, and compares the reference voltages + Vr and -Vr with the input signal. In this case, the comparator circuit 14a outputs an "H" level signal when the input signal voltage is lower than the reference voltage -Vr, and outputs an "L" level signal when the input signal voltage is higher than the reference voltage -Vr. Further, the comparison circuit 14b outputs an "L" level signal when the input signal voltage is lower than the reference voltage + Vr, and outputs an "H" level signal when the input signal voltage is higher than the reference voltage + Vr. Further, the comparison circuit 14c outputs an "H" level signal when the input signal voltage is between the reference voltages + Vr and -Vr, and outputs an "L" level signal otherwise.

Reference numeral 19 denotes a pulse generating circuit, which outputs a narrow pulse signal P1 after a time T4 (for example, 150 μsec) shown in FIG. 2B from the time when the pulse signal P is received. A monostable multivibrator 20 receives the pulse signal P and outputs a pulse signal P2 having a pulse width of time T3 (for example, 57 μsec) shown in FIG. 2A. 15a
15 to 15c are AND gates, 18 is an inverter, 16 is an OR gate, and 17a and 17b are memories.

B. Operation Next, the operation of the embodiment shown in FIG. 1 will be described. (1) When arc discharge occurs in the cell 6 and commutation failure of the thyristor does not occur FIG. 2A is a diagram showing a waveform of the interelectrode voltage VR of the cell 6 in this case. In this figure, a period T1 is a period in which the thyristors 3-1 and 3-4 shown in FIG. 3 are turned on, a period in which the signal S is at "H" level, and a period T2 is a period in which the thyristors 3-2 and 3-3 are turned on. This is the period when the signal is on, and the signal S is "L".
It is a period to reach the level. Further, in the figure, the broken line indicates a normal case, and the solid line L1 indicates a case where arc discharge occurs. As shown in this figure, in the normal case, the voltage VR becomes 0 after the time T3 from the commutation of the thyristor.
When arc discharge occurs, the voltage VR becomes a negative value before the time T3 elapses. Therefore, in this embodiment, the pulse width of the output pulse P2 of the monostable multivibrator 20 in FIG. 1 is set to T3, and when the signal S is at the "L" level, the voltage VR is the voltage − shown in FIG. When it is smaller than Vr, it is determined to be abnormal.

That is, when arc discharge occurs, the voltage VR attenuates as shown by the solid line L1 in the figure. And time tc
At, the voltage VR becomes smaller than the voltage -Vr. When the voltage VR becomes lower than the voltage -Vr, the output of the comparison circuit 14a becomes "
It becomes H "level and is supplied to the AND gate 15a.
At this time, the signal S is at "L" level, and therefore the output of the inverter 18 is at "H" level. The output of the monostable multivibrator 20 is also at "H" level. As a result, when the "H" level signal is output from the comparison circuit 14a, the "H" level signal is output from the AND gate 15a, and the memory 17 is supplied via the OR gate 16.
is supplied to a. As a result, the abnormality occurrence is written in the memory 17a. At this time, since the signal S is "L", the AND gate 15b is in the closed state, and the output of the comparison circuit 14b does not affect the circuit operation.

On the other hand, when the signal S is at "H" level and attenuation occurs due to arc discharge, the voltage V is increased while the output of the monostable multivibrator 20 is at "H" level.
A state occurs in which R exceeds the voltage + Vr. At this time, the output of the comparison circuit 14b becomes "H" level, and this "H" level signal is supplied to the memory 17a via the AND gate 15b and the OR gate 16.

(2) When arc discharge is generated in the cell 6 and commutation failure of the thyristor occurs due to this, FIG. 2 (b) is a diagram showing a change in the voltage VR in this case, and as shown in FIG. When the commutation failure occurs, the voltage VR becomes 0 thereafter (see the straight line L2). On the other hand, in the normal case, as shown by the broken line, the voltage VR never becomes 0 except at the time point 1. So, in this embodiment,
In a normal case, the voltage VR is checked at a time when it never becomes 0, that is, at a time td after (1/4) cycle + α after commutation, and if -Vr <VR <+ Vr, then commutation is performed. Judge as a failure.

That is, when commutation of the thyristor occurs,
The pulse signal P is output from the power supply unit 11 and supplied to the pulse generation circuit 19. The pulse generation circuit 19 receives the pulse signal P, starts the time measurement, and outputs the "H" level pulse signal P1 when the time T4 shown in FIG. 2B has elapsed. At this time, if the voltage VR is 0, the output of the comparison circuit 14c becomes "H" level. As a result, the pulse signal P1 is supplied to the memory 17b via the AND gate 15c, whereby the abnormality occurrence due to the commutation failure is written in the memory 17b. On the other hand, when the pulse signal P1 is output, the voltage VR is VR <−
If Vr or VR> + Vr, the comparison circuit 14
Since the output of c is at "L" level, the pulse signal P1 is not supplied to the memory 17b.

The above is the details of the embodiment shown in FIG. The reason why the comparison level is not set to 0 in the above-described comparison circuits 14a and 14b is that if it is set to 0, the commutation failure is detected. The present invention can also be used in the case where the power supply unit is composed of an element other than the thyristor.

[0019]

As described above, according to the abnormality detecting circuit of the ozonizer of the present invention, when the arc discharge occurs between the electrodes of the cells of the ozonizer, it can be surely detected. In particular, when it is used for an ozonizer using a thyristor, there is an advantage that the arc discharge can be reliably detected even when the commutation failure of the thyristor does not occur.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an electric circuit of an ozonizer according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a waveform of a voltage VR between electrodes of a cell in the example.

FIG. 3 is a schematic configuration diagram showing an example of an electric circuit of a conventional ozonizer.

FIG. 4 is a diagram showing an example of a voltage waveform between electrodes of a conventional ozonizer.

FIG. 5 is a diagram showing a voltage waveform between electrodes when commutation fails in the conventional ozonizer.

FIG. 6 is a diagram showing a voltage waveform between electrodes when commutation is performed in the conventional ozonizer despite the occurrence of abnormality in the cell.

[Explanation of symbols]

 6 cell 12 transformer 13 waveform shaping circuit 14a, 14b, 14c comparison circuit 17a, 17b memory 19 pulse generation circuit 20 monostable multivibrator

Claims (3)

[Claims] 1. An ozonizer comprising a power supply section for generating a high-frequency voltage and an ozone generation section to which an output voltage of the power supply section is applied, wherein the voltage detection means detects an output voltage of the power supply section, and the power supply. A first comparison means for comparing the detected voltage of the voltage detection means with a reference voltage within a first predetermined time after the output voltage of the section is inverted, and an output of the first comparison means is provided. An abnormality detecting circuit for an ozonizer, wherein the abnormality detecting circuit detects an abnormality in the ozone generating portion based on the abnormality detecting circuit. 2. An ozonizer comprising a power supply section for generating a high frequency voltage and an ozone generation section to which the output voltage of the power supply section is applied, wherein the voltage detection means detects the output voltage of the power supply section, and the power supply. A first comparing means for comparing the detection voltage of the voltage detecting means with a reference voltage within a first predetermined time after the output voltage of the power supply section is inverted; 2 is provided with second comparing means for comparing the detected voltage of the voltage detecting means after a lapse of a predetermined time with a reference voltage, and the ozone generator is based on the outputs of the first and second comparing means. An abnormality detection circuit for an ozonizer, which detects abnormality in the 3. The power supply unit has a DC-AC conversion unit using a thyristor, and the first and second comparing means count the predetermined time from a commutation point of the thyristor. The abnormality detection circuit for an ozonizer according to claim 1 or claim 2.