JP2001232241A - Electric dust collector and power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric dust collector suppressing spark discharge and having an enhanced efficiency of dust collection. SOLUTION: The electric dust collector 1 is composed of an electric dust collector main body 2 having a spark electrode 7 and a counter electrode 6, a power source device 3 and a control device 20 controlling the power source device 3. The output voltage Vo of the power source device 3 is detected by a voltmeter 13 and the power source current Io is detected by an ammeter 12. The control device 20 inputs a preset voltage Voset and a preset current Ioset to the power source device 3 in accordance with detected values. The power source device 3 is controlled so that the output voltage Vo or output current Io becomes the inputted preset voltage Voset or preset current Ioset. The control device 20 adjusts the preset voltage Voset at the neighborhood of the rated voltage Vb in such a manner that the power source keeps the constant value of the preset current Ioset. Thus, the increase of a flow of electricity is prevented at the generation of spark discharge and the development of spark discharge is prevented. And, thereby the efficiency of dust collection is also enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric precipitator for removing dust from air in a tunnel, for example, and a power supply for the same.

[0002]

2. Description of the Related Art A typical configuration of an electric dust collector is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-52381. The electric dust collector includes a dust collector body, a power supply device, and a control device. The dust collector body has a charging unit and a dust collecting unit. A high voltage is applied to an electrode provided on the charging unit by a power supply device, and the power supply device is controlled by a control device.

[0003] The electrode of the charging section to which a high voltage is applied generates corona discharge, and when the gas containing the dust flows between the electrodes, the dust is charged. Electrodes are also provided on the dust collecting portion disposed downstream of the charging portion, and the charged dust is attracted to the electrodes of the dust collecting portion by electrostatic force and collected. The adsorbed dust is removed by spraying water on the electrodes.

[0004] The power supply of the electric precipitator controls the output voltage Vo so as to be the set voltage Voset input from the control device. In a conventional electrostatic precipitator, the output voltage V
set voltage Vos so that o is kept constant at the rated voltage Vb.
Constant voltage control was performed with et = rated voltage Vb.

FIG. 15 is a graph showing the relationship between current and voltage during rated operation of a conventional electric precipitator that performs constant voltage control. As shown in this graph, Voset = Vb is set so that the output voltage Vo is always maintained at the rated voltage Vb.
When the output voltage is kept constant, the impedance (electrical resistance) of the discharge space of the electrostatic precipitator and the precipitator,
The output current is determined secondarily.

The impedance in the discharge space changes every moment due to changes in the discharge electrode such as deterioration and fouling of the electrode, and changes in the discharge space such as temperature, humidity, and dust amount. Due to the constant voltage control, it appears as a current fluctuation as shown by the range of the arrow in FIG.

Further, the power supply generally has a sufficient current capacity so that the voltage between the electrodes does not fluctuate due to the current fluctuation.

[0008]

However, when a spark discharge occurs in such a configuration, the current capacity causes the spark discharge to progress. FIG. 16 is a time chart showing the output voltage Vo and the output current Io when a spark discharge occurs.

The electric precipitator is controlled so as to be maintained at the set voltage Voset. When a spark discharge occurs at time t1, the electric precipitator attempts to maintain the voltage at Voset. And the output current Io
Increases to the maximum current Imax (time t2).

However, this increase in current causes an avalanche (formation of a streamer and a leader) in the discharge space, which causes a spark discharge to progress, and consequently, an arc discharge state (electrical conduction in the discharge space, insulation breakdown). State), and the voltage Vo drops (time t3).

When a spark discharge is detected based on an overcurrent and a voltage drop, the spark discharge protection function of the power supply temporarily sets the set voltage Voset to 0 V to extinguish the spark discharge. Then, the current Io also decreases (time t4).

Thereafter, the set voltage Voset is gradually increased to restore the power supply voltage, and the current is thereby restored, thereby recovering the normal state (time t5). Therefore, the operation region at the time of occurrence of spark discharge exists in the hatched region in FIG.

As described above, the conventional dust collector has a problem that when a spark discharge occurs, the spark discharge is advanced. In addition, when the spark discharge is extinguished and then returned to a normal state, the set voltage Voset is gradually increased, so that it takes time to return to the normal state, thereby reducing the dust collection efficiency. Have a problem.

An object of the present invention is to provide an electric precipitator in which spark discharge is quickly suppressed and dust collection efficiency is improved. Another object of the present invention is to provide a power supply device for an electric precipitator, which can suppress generation of spark discharge and can be downsized.

[0015]

According to the first aspect of the present invention, a dust-containing gas is passed between electrodes to which a predetermined rated voltage is applied by a power supply device to charge the dust, and the electrostatic force is applied to the dust. In an electrostatic precipitator for collecting dust, a voltmeter for detecting an output voltage of a power supply, an ammeter for detecting an output current of the power supply, an output voltage detected by the voltmeter, an output current detected by the ammeter, and a preset value. A control device that calculates a set voltage and a set current based on the rated voltage to be input to the power supply device, and the power supply device outputs the set voltage based on the output voltage detected by the voltmeter and the input set voltage. And a function of controlling the output current to be the set current based on the output current detected by the ammeter and the input set current. With the set current input to the power supply unit kept constant, calculate the set voltage so that the output current is kept at the set current and the output voltage becomes close to the rated voltage and input it to the power supply unit. It is an electric precipitator characterized by the above.

In the power control of the electric precipitator of the present invention, as shown in the graph of FIG. 1, the control device controls the set current Ios input to the power supply so that the output current Io is kept constant.
With the value of et maintained constant, the set voltage Voset is adjusted near the rated voltage Vb to perform constant current control. Therefore, as shown in the time chart of FIG. 2, when the spark discharge occurs at time t1, the current Io is maintained at the set current Ioset by the control of the power supply device, and the output current Io is prevented from increasing. This prevents the progress of spark discharge.
Therefore, even if a spark discharge occurs, as shown in FIG. 2, the output voltage Vo and the output current Io only slightly fluctuate, the arc is extinguished immediately, and the normal state can be quickly restored.

Further, at time t2 in FIG. 2, when the generated spark discharge is steep and immediately shifts to arc discharge,
By not allowing the current equal to or greater than the set current Ioset to flow by the constant current control, the output voltage Vo immediately drops. For this reason, the arc of the spark discharge is quickly extinguished, and the time required to return to a normal state is faster than that of the constant voltage control of the related art. Therefore, the operation region when the spark discharge occurs exists in the hatched region in FIG.

With these features, a reduction in dust collection efficiency due to the occurrence of spark discharge is suppressed to a minimum. Further, by suppressing the spark discharge, damage to the electrodes used in the charging unit and the dust collecting unit can be minimized.

Further, the spark discharge detection circuit operates mainly based on a voltage drop. When spark discharge is detected, the circuit is operated at a low voltage for a predetermined time to prevent spark generation. In the present invention, a large voltage drop does not occur in the slight spark discharge generated at time t1 in FIG.
Since only the severe spark discharge in No. 2 is detected, the operation time due to low voltage for preventing spark generation can be minimized, which also improves dust collection efficiency.

According to a second aspect of the present invention, there is provided the control device,
When the output voltage detected by the voltmeter becomes larger than the vicinity of the rated voltage, the set current is reduced by a reference current of a predetermined value, and when the detected output voltage becomes smaller than the vicinity of the rated voltage, The set current is increased by the reference current.

According to the present invention, the detected output voltage Vo
However, when the voltage exceeds the rated voltage Vb, the set current Ioset is decreased. As a result, the output voltage Vo decreases. Similarly, when the detected voltage Vo becomes lower than the rated voltage Vb, the set current Ioset is increased and the output voltage Vo
increase o.

In the constant current control, the power supply voltage is secondarily determined by the impedance of the discharge space, and changes every moment due to the change of the state of the discharge space. Regardless of
The constant current control can be performed with the power supply voltage substantially at the rated voltage.

According to a third aspect of the present invention, at the time of starting to increase the output voltage to the rated voltage, the control device includes:
The present invention is characterized in that the set voltage is set to be equal to or higher than the rated voltage, and the set current is changed based on an increase in the output current after a predetermined time from the input of the set current to the power supply device.

According to the present invention, at the start-up time when the power supply voltage is increased from 0 [V] to the rated voltage Vb [V], the set voltage Voset is set in advance to the rated voltage Vb or more, and the set current Ioset is supplied to the power supply device. input. Then, the power supply voltage starts to rise. Then, if the detected output voltage Vo does not reach the rated voltage Vb, for example, after the elapse of the predetermined time, it is determined that the set current Ioset is low, and the setting current Ioset is changed to be increased. In this way, it is possible to obtain an optimal set current Ioset such that the output voltage Vo is stabilized near the rated voltage Vb.

According to a fourth aspect of the present invention, there is provided the power supply device,
An inverter that converts low-voltage DC power into high-frequency AC power; a high-frequency transformer that is connected to the inverter and boosts the high-frequency AC output voltage of the inverter; and that is connected to the secondary side of the high-frequency transformer and boosts the high-frequency AC output voltage And a rectifier that rectifies and outputs the voltage to the main body of the electrostatic precipitator, and an inverter control device that controls the inverter so that the DC output voltage or DC output current of the voltage rectifier becomes the input set voltage or set current. It is characterized by the following.

According to the present invention, the power supply device once converts low-voltage DC power into high-frequency AC power, and then converts it into high-voltage DC power and supplies it to the main body of the electric dust collector. Since the rectification is performed after the DC power is once converted into the high-frequency AC power in this manner, the power supply frequency of Expression (1) described later increases, and the pulsation rate of the DC output voltage of the power supply device can be reduced. . That is, it is possible to reduce the ripple which is the AC component in the DC component output from the power supply device. Therefore, the peak value of the output voltage due to the ripple is unlikely to exceed the spark discharge generation voltage, and the occurrence of spark discharge can be suppressed. As described above, although the generation of spark discharge is suppressed by the constant current control of the control device, by reducing the ripple in this manner, the spark discharge suppression effect by the constant current control and the spark discharge suppression effect by the reduction of the ripple are reduced. Is added, and the spark discharge suppressing effect can be further enhanced.

According to a fifth aspect of the present invention, there is provided a rectifier for converting low-frequency low-voltage AC power into low-voltage DC power and outputting the low-voltage DC power to an inverter.

According to the present invention, since the low-frequency low-voltage AC power can be converted to the low-voltage DC power by the rectifier, a 50 Hz or 60 Hz commercial AC power supply can be used as a power source. Therefore, a power source can be easily and stably secured.

According to a sixth aspect of the present invention, there is provided a voltage comparison control circuit for determining a difference between an output voltage of a voltage doubler rectifier and a set voltage, and transmitting a signal corresponding to the determined difference to an inverter control device.
A current comparison control circuit that determines a difference between the output current of the voltage doubler rectifier and the set current, and sends a signal corresponding to the determined difference to an inverter control device, wherein the inverter control device outputs the voltage or the output of the current comparison control circuit. And controlling the inverter such that the DC output voltage or the DC output current of the voltage doubler rectifier becomes the input set voltage or set current.

According to the present invention, the voltage comparison control circuit determines the difference between the output voltage of the voltage doubler rectifier and the set voltage, generates a voltage control signal corresponding to the determined difference, sends it to the inverter control device, The comparison control circuit similarly generates a current control signal and sends it to the inverter control device. The inverter control device controls the inverter so that each control signal becomes zero. Thereby, the output voltage or the output current of the voltage doubler rectifier is quickly and accurately controlled to become the set voltage or the set current, so that the stability of the power supply device can be improved.

According to a seventh aspect of the present invention, the inverter control device is a pulse width modulator.

According to the present invention, since the inverter control device is a pulse width modulator, it is possible to control the inverter quickly and accurately so that the output voltage and the output current of the voltage doubler rectifier become the set voltage and the set current. Can be.

According to the present invention, the doubler rectifier is a Cockcroft-Walton circuit.

According to the present invention, the voltage doubler rectifier is a Cockcroft-Walton circuit, which is described in FIG.
Since a plurality of diodes and the same number of capacitors are arranged as shown in (1), when the number of capacitors is n, the output voltage can be set to n times the secondary voltage of the high-frequency transformer. Therefore, the output voltage can be easily increased to a high voltage. Also, in the Cockcroft-Walton circuit, the voltage applied to each capacitor is twice the secondary voltage of the high frequency transformer, so that a high voltage can be obtained with a capacitor of the same rating.

According to a ninth aspect of the present invention, there is provided an inverter for converting low-voltage DC power into high-frequency AC power, a high-frequency transformer connected to the inverter and boosting the high-frequency AC output voltage of the inverter, and a high-frequency transformer. Connected to the next side,
A doubler rectifier that boosts and rectifies the high-frequency AC output voltage and outputs it to the main body of the dust collector, and controls the inverter so that the DC output voltage or DC output current of the doubler rectifier becomes the input set voltage or set current. A power supply device for an electric dust collector, comprising: an inverter control device.

According to the present invention, the power supply device converts low-voltage DC power into high-frequency AC power by an inverter,
It is converted to high-voltage DC power by a high-frequency transformer and a doubler rectifier. Since the rectification is performed after the DC is once converted to the high-frequency AC, the pulsation rate of the DC output voltage of the power supply device can be reduced as described above, and the ripple can be reduced. Therefore, generation of spark discharge can be suppressed. In addition, the inverter control device controls the inverter by, for example, high-frequency pulse control, so that a high-voltage output can be obtained with high efficiency.
Power saving can be achieved. Since the output voltage of the power supply device is boosted in two stages by the high frequency transformer and the voltage doubler rectifier, a high voltage can be easily obtained and the secondary voltage of the high frequency transformer can be set low. In addition, the number of turns of the high-frequency transformer can be reduced by lowering the voltage and increasing the frequency, so that the number of turns of the high-frequency transformer can be reduced by once converting to high frequency and then rectifying. Therefore, the size and weight of the high-frequency transformer can be reduced.

[0037]

FIG. 3 is a diagram showing the overall configuration of an electric dust collector 1 according to an embodiment of the present invention. The electric dust collector 1 is used, for example, to remove dust in a tunnel, and is installed in a dust collection tunnel that bypasses a roadway tunnel. A blower is provided in the dust collection tunnel, and the air in the roadway tunnel containing the dust is drawn into the dust collection tunnel, passed through the electric dust collector 1 to remove the dust, and the dust-removed air is again used for the roadway. Return to the tunnel.

The electric dust collector 1 includes a dust collector main body 2 disposed in a dust collecting tunnel, a power supply device 3 as a power supply of the dust collector main body 2, and a control device 20 for controlling the power supply device 3. The dust collector main body 2 includes a charging unit 4 arranged on the upstream side in the blowing direction and a dust collecting unit 5 arranged on the downstream side in the blowing direction in the dust collecting tunnel.

The charging section 4 has a plurality of discharge electrodes 7 and a plate-like counter electrode 6 disposed between the discharge electrodes 7 and facing the discharge electrodes 7. The discharge electrode 7 has a sawtooth shape as shown in FIG. That is, a plurality of triangular teeth 8 are formed on both sides of the strip-shaped electrode body 9 in a longitudinal direction. The triangular teeth 8 are alternately bent, and are provided on two opposing electrodes 6 sandwiching the discharge electrode 7 so that the teeth 8 alternately face each other. In the present embodiment, the number of the teeth 8 is about 10 per inch, and the interval between the discharge electrode 7 and the counter electrode 6 is 5 to 30 mm, for example, 20 mm.

In the dust collecting part 5, a plurality of pairs of plate-shaped dust collecting electrodes 10 and 11 facing each other are arranged in parallel. The counter electrode 6 of the charging unit 4 and one of the dust collecting electrodes 10 of the dust collecting unit 5 are grounded, and the discharge electrode 7 of the charging unit 4 and the other dust collecting electrode 11 of the dust collecting unit 5 are connected to the power supply device 3. And a high voltage is applied.

In the charging section 4, a corona discharge occurs, and when dust-containing air flows through the charging section 4, the dust is charged by the corona discharge. When the charged dust flows through the dust collecting section 5, an electrostatic force is generated. Thereby, it is adsorbed to the dust collecting electrode 10. In this way, dust in the air is removed. Further, the electrode on which the dust is adsorbed is removed by spraying water at regular intervals.

In this embodiment, since the discharge electrode 7 of the charging section 4 has a saw-tooth shape, dust can be charged efficiently. The output voltage Vo of the power supply 3, which is the voltage between the electrodes 6 and 7 of the charging unit 4, is detected by the voltmeter 13 and the output current I of the power supply 3 flowing to the discharge electrode 7 is output.
o is detected by the ammeter 12.

FIG. 5 is a block diagram showing an electrical configuration of the control device 20 and the power supply device 3 of the electric precipitator 1. The power supply 3 receives the set voltage Vos input from the controller 20.
Based on et and the output voltage Vo detected by the voltmeter 13, the power supply voltage is controlled so that the output voltage Vo becomes the set voltage Voset, and the output current Io detected by the ammeter 12 and the setting input from the control device 20. The power supply current is controlled based on the current Ioset so that the output current Io becomes the set current Ioset.

The power supply device 3 includes a current comparison control circuit 21, a voltage comparison control circuit 22, a phase control device 3, and a thyristor 2.
5. It is composed of a transformer 26 and a rectifier 27. The thyristor 25 controls the phase of the commercial AC power supply 29 at 50 Hz or 60 Hz according to the control signal C from the phase control device 23. The phase-controlled power supply voltage is applied to the transformer 2
6 and rectified by the rectifier 27 to obtain a high-voltage DC power supply. The high voltage thus obtained is output and applied to the discharge electrode 7 of the dust collector main body 2.

The output current Io detected by the ammeter 12 is supplied to a current comparison control circuit 21 and a control device 20. The output voltage Vo detected by the voltmeter 13 is
It is provided to voltage comparison control circuit 22 and control device 20. The control device 20 sets the set voltage Voset and the set current Io based on the detected output voltage Vo and output current Io.
The set is calculated and input to the current comparison control circuit 21 and the voltage comparison control circuit 22.

The current comparison control circuit 21 supplies a signal corresponding to the difference between the input set current Ioset and the output current Io to the phase control device 23.
Is given to the thyristor 25. That is, the control signal C controls the phase of the thyristor 25 so that the output current Io becomes the set current Ioset. In this manner, the current control is performed by the current comparison control circuit 21. Further, the current control state signal CC indicating the current control state of the current comparison control
Is input to

Similarly, the voltage comparison control circuit 22 supplies a signal corresponding to the difference between the set voltage Voset and the output voltage Vo to the phase control device 23, and the phase control device 23 performs control so that this signal becomes zero. The signal C is given to the thyristor 25. As a result, the output voltage Vo is controlled so as to become the set voltage Voset. In this way, the voltage control is performed by the voltage comparison control circuit 22, and the voltage control state signal CV indicating the voltage control state is input to the control device 20.

Next, a power control method of the control device 20 when the electric precipitator 1 is started will be described with reference to a flowchart shown in FIG. In the control device 20, a maximum voltage Vomax, a maximum current Imax, a rated voltage Vb which is a voltage during a rated operation of the electrostatic precipitator, a reference voltage ΔV which is a predetermined voltage value, and a reference current ΔI which is a predetermined current value are set. I have. In this embodiment, for example, the rated voltage Vb is 1
5 kV and the maximum current is 100 mA.

At the start of step a1, the set voltage Voset and the set current Ioset are 0 [V], respectively.
These are set to 0 [A], and these are input to the current comparison power supply 21 and the voltage comparison power supply 22, respectively.

In the next step a2, first, the maximum voltage Vomax is set to the set voltage Voset, and the set voltage Voset is input to the voltage comparison control circuit 22. At this time, the set current Ioset is 0
[A], the output voltage Vo becomes 0 [V]. In step a3, the current set current Ioset, here 0
A new set current Ioset obtained by adding the reference current ΔI to [A]
Is input to the current comparison control circuit 21. Then
The power supply 3 sets the maximum voltage Vmax at the set current Ioset.
And the output voltage Vo increases.

Then, in step a4, a predetermined time is counted by a timer.
It is determined whether or not the output voltage Vo has become equal to or higher than the rated voltage Vb. If the rated voltage Vb has not been reached, it is determined in step a6 whether or not the set current Ioset is equal to or greater than the maximum current Imax. If the set current Ioset has not reached the maximum current Imax, the process returns to step a3 again, and Current Δ
A new set current Iset to which I is added is set.

That is, if the set current Ioset is low, the output voltage Vo does not reach the rated voltage Vb, so the set current Ioset is increased in order. In this manner, the set current Ioset is increased until the set current Ioset corresponding to the state of the discharge space is obtained.

The above control is repeated, and step a5
When the output voltage Vo becomes equal to or higher than the rated voltage Vb, or when the set current Ioset becomes equal to or higher than the maximum current Imax in step a6, the process proceeds to the next step a7.

In step a7, the current set voltage Voset
A new set voltage Voset is set by subtracting the reference voltage ΔV from the reference voltage ΔV. Then, after a predetermined time is counted by the timer in step a8, in step a9, the set voltage Voset is changed to the rated voltage Vb.
It is determined whether or not it is below. If the set voltage Voset exceeds the rated voltage Vb, the process returns to step a7, and the reference voltage ΔV is further subtracted from the set voltage Voset to lower the set voltage Voset. In this way, when it is determined in step a9 that the set voltage Voset has dropped below the rated voltage Vb, in step 10, the reference voltage ΔV is added to the current set voltage Voset, and the start is completed in step a11. In this way, when the startup is completed, the set voltage V
Oset can be set to a state very close to the rated voltage Vb, and the set current Ioset can be set to an optimum value according to the state of the discharge space.

In this embodiment, the start-up control is performed so that the set voltage Voset becomes very close to the rated voltage when the start-up is completed.
Not limited to such an activation control method, for example, step a
When the output voltage Vo becomes equal to or more than the rated voltage Vb in step 5, or when the set current Ioset becomes equal to or more than the maximum current Imax in step a6, the start-up may be completed.
In 9, the startup may be completed when it is determined that the set voltage Voset has become equal to or lower than the rated voltage Vb.

Next, a power supply control method at the time of rated operation after the start-up is completed will be described with reference to a flowchart shown in FIG.

At the start of step b1, the set voltage Voset is set to the rated voltage Vb and the set current Iose
t is set to the set current Ioset at the time of completion of startup.

In the next step b 2, the control device 20 sets the set current I inputted to the current comparison control circuit 21.
With oset kept constant, the output current Io is determined based on the output voltage Vo detected by the voltmeter 13, the output current Io detected by the ammeter 12, and the voltage control state signal CV from the voltage comparison control circuit 22. A set voltage Voset maintained at the set current Ioset is calculated and input to the voltage comparison control circuit 22.

As described above, the control device 20 outputs the output current I
not only based on the voltage control state signal CV indicating the voltage control state of the voltage comparison control circuit 22 but also the set current Ios
Since the set voltage Voset is adjusted to be kept at et, the output current Io can be maintained at the set current Ioset with high accuracy.

In the constant current control in step b2, if the detected output voltage Vo is determined to be lower than the rated voltage Vb,
Proceeding to step b3, the output voltage Vo becomes the set voltage Voset,
That is, it is determined whether or not the voltage is near the rated voltage Vb. In the present embodiment, it is determined whether or not the output voltage Vo is within ± 5% of the rated voltage Vb. If the output voltage Vo is near the rated voltage Vb, the process returns to step b2, and the constant current control is continued. In this way, the output current Io is kept constant while the output voltage Vo is near the rated voltage Vb. By performing the constant current control in this manner, as described above, even if a spark discharge occurs, it is quickly suppressed, and the progress of the spark discharge is prevented.

In step b2, when the detected output voltage Vo becomes equal to or higher than the rated voltage Vb while the constant current control is being performed, the process proceeds to step b4.

For example, when the state of the discharge space changes and the output voltage Vo exceeds the rated voltage Vb by the constant current control, it is determined that the set current Ioset is high, and in step b4, the reference current ΔI is subtracted from the set current Ioset. New set current I
oset is calculated and input to the current comparison control circuit 21. In response to this, the output current Io is controlled to become the new set current Ioset, and the output voltage Vo also starts to decrease.

After a predetermined time is counted by the timer in the next step b5, the process returns to step b2, and the constant current control is performed again. Here, if the output voltage Vo is still higher than the rated voltage Vb, the process proceeds to step b4 again, and the set current Ioset is reduced.

If the output voltage Vo deviates from the vicinity of the set voltage Voset in step b3 described above, step b6
Then, a new set current Ioset obtained by adding the reference current ΔI to the set current Ioset is calculated and input to the current comparison control circuit 21. As a result, the output voltage Vo increases. Next, after a predetermined time is counted by the timer in step b5, the process returns to step b2, and constant current control is performed based on the new set current Ioset.

As described above, during the rated operation, the constant current control is performed by changing the set current Ioset in accordance with the change in the discharge space, so that the output voltage Vo is substantially equal to the rated voltage Vb.
Is kept.

Next, another control method of the control device 20 when the electric precipitator 1 is started will be described with reference to the flowchart of FIG.

At the start of step c1, the set voltage Voset is set to 0 [V], and the set current Ios
et is set to 0 [A]. In the next step c2, a new set voltage Voset obtained by adding the reference voltage ΔV to the current set voltage Voset is set, and the voltage comparison control circuit 2
Enter 2 Then, the power supply device 3 increases the power supply voltage.

After a predetermined time is counted by the timer in step c3, if the output voltage Vo exceeds the set voltage Voset in step c4, the process returns to step c2, and the set voltage V
The reference voltage ΔV is added to oset. Such control is repeated to set the set current Ioset constant, and first increase the power supply voltage.

If the set voltage Voset is equal to or higher than the output voltage Vo at step c4, the process proceeds to step c5, where the reference current ΔI is added to the set current Ioset, and the new set current Ioset is set.
oset is calculated. Then, the power supply device 3 increases the power supply current.

After a predetermined time is counted by the timer in the next step c6, the output current Io is changed to the set current Io in step c7.
If it exceeds set, the process returns to step c5, and the reference current ΔI is further added to the current set current Ioset to set a new set current Ioset. By repeating such control, the set voltage Voset is kept constant to increase the power supply current.

If the set current Ioset is equal to or more than the output current Io in step c7, the next step c8
It is determined whether the set voltage Voset is equal to or higher than the rated voltage Vb. Here, if the set voltage Voset is smaller than the rated voltage Vb, the process returns to step C2 to perform the voltage increase control and the current increase control.

In this way, the voltage is increased to make the set voltage Voset equal to or higher than the rated voltage Vb. If it is determined in step c8 that the set voltage Voset is equal to or higher than the rated voltage Vb, then in step c9, the set voltage Voset is increased to the set voltage Voset. The set voltage Voset is updated by adding the reference voltage ΔV. Then, the power supply device 3 raises the power supply voltage so as to become the updated set voltage Voset. After a predetermined time is measured by the timer in step c10, if the output voltage Vo exceeds the set voltage Voset in step c11, the process proceeds to step c9. Then, the reference voltage ΔV is added to the set voltage Voset for updating. Such a control is repeated to update the set voltage Voset. After a predetermined time has elapsed, if the set voltage Voset is equal to or higher than the output voltage Vo, it can be determined that the power supply voltage is in a stable state, and the process proceeds to step c12 to determine that the startup is completed. I do. Thus, the power supply voltage can be stably raised to the rated voltage Vb.

Next, another embodiment of the power supply device of the electric precipitator will be described with reference to FIG. FIG. 9 is a block diagram showing an electrical configuration of a power supply device 30 of an electric dust collector according to another embodiment of the present invention. The power supply device 30 includes a current comparison control circuit 21, a voltage comparison control circuit 22, an inverter control device 31, a rectifier 32, and an inverter 33.
, A high-frequency transformer 34 and a voltage doubler rectifier 35. Components corresponding to the power supply device 3 are denoted by the same reference numerals, and description thereof will be omitted. The other configuration of the electric precipitator in the present embodiment is the same as the configuration of the electric precipitator 1. That is, the control device 20 suppresses the generation of the spark discharge by the constant current control as described above.

In the power supply device 30, 50 Hz or 60 H
The low-frequency low-voltage AC power of the z commercial AC power supply 29 is rectified by the rectifier 32 and is once converted to low-voltage DC power. Rectifier 32 is formed of, for example, a diode. The converted low-voltage DC power is converted into high-frequency AC power by the inverter 33. The inverter 33 includes a switching circuit including a transistor, and generates a low-voltage high-frequency AC pulse. High frequency AC pulse frequency is 20 ~ 3
Preferably, the frequency is set to 5 kHz. Inverter 33
The high-frequency AC output voltage is converted to a medium-frequency high-frequency AC voltage by a high-frequency transformer 34 connected to the inverter 33. The high-frequency transformer 34 is, for example, a silicon transformer. Further, the medium-voltage high-frequency AC voltage of the high-frequency transformer 34 is supplied to the voltage doubler rectifier 3 connected to the secondary side of the high-frequency transformer 34.
5, the electric dust collector body 2 is rectified and rectified.
Is applied to the discharge electrodes 7.

As described above, since the commercial AC power source 29 is used as the low-frequency low-voltage AC power source, the power source can be easily and stably secured. The rectifier 32 may not be a diode, and the high-frequency transformer 34 may not be a silicon transformer.

The voltage comparison control circuit 22 includes a voltage doubler rectifier 35
And a voltage control signal corresponding to the determined difference is generated and sent to the inverter control device 31. The current comparison control circuit 21 The difference between the output current of 35 and the set current input from the control device 20 is obtained, and a current control signal corresponding to the obtained difference is generated and sent to the inverter control device 31. As a result, the output voltage and the output current of the voltage doubler rectifier 35 are quickly and accurately controlled to become the set voltage and the set current, so that the stability of the power supply device 30 can be improved.

The inverter control device 31 is a pulse width modulator. By applying a control signal C to the inverter 33, the inverter 33 modulates the pulse width of the high-frequency AC pulse of the inverter 33 to perform switching output control. The power supply output voltage and the power supply output current of the power supply 35 are controlled. Therefore, based on the voltage control signal from the voltage comparison control circuit 22, the inverter control device 31 gives the inverter 33 a control signal C such that the power supply output voltage becomes the set voltage Voset. Similarly,
Based on the current control signal from the current comparison control circuit 21,
The inverter control device 31 determines that the power supply output current is
A control signal C that is set to oset is given to the inverter 33.

Even in the power supply device 30 using such a high frequency, the constant current control is performed by the control device 20 in the same manner as described above, so that when a spark discharge occurs, the spark discharge is prevented from progressing. The arc can be extinguished quickly. In addition, by once converting to high-frequency AC and then rectifying, it is possible to reduce the voltage fluctuation rate and ripple, improve the stability, and suppress the occurrence of spark discharge.
The reason why the ripple can be reduced by once converting into a high-frequency AC and then rectifying it is as follows.

FIG. 10 is a graph showing the temporal transition of the DC output voltage E1, the AC secondary voltage E0 of the transformer, and the output current Ao of the transformer in the rectifier circuit. The rectifier circuit includes a transformer, a rectifier, and a capacitor. Transformer AC 2
When comparing the next voltage E0 and the DC output voltage E1, FIG.
As shown in (a), after the peak point a1 of the DC output voltage E1, the AC secondary voltage E0 of the transformer becomes lower than the DC output voltage E1, so that the charge of the capacitor charged between the points b1 and a1 is exponential. Discharges functionally. Further, after the point b2, the AC secondary voltage E0 of the transformer becomes higher than the DC output voltage E1, so that the capacitor is charged again by the transformer output current Ao as shown in FIG. This charging ends at the next peak point a2 of the DC output voltage E1.
Accordingly, the DC output voltage E1 gradually decreases between the points a1 and b2, and the DC output voltage E1 increases between the points b2 and a2.

Since the fluctuation of the DC output voltage E1 is periodically repeated, the DC output voltage E1 has a pulsating flow. The pulsation component (AC component) included in the DC component is called ripple. Here, the instantaneous maximum value of the DC output voltage E1 (a
1 point) and the instantaneous minimum value (point b2) is the pulsating voltage ΔE
Called. The smaller the pulsation voltage ΔE, the closer to the DC voltage, the pulsation rate (ripple rate) R is used as an index indicating the degree. The pulsation rate R is represented by i being the average value of the output current, C being the capacitance of the capacitor, f being the power supply frequency, Et
Is the average value of the output voltage, it is expressed by equation (1).

R = ΔE / Et = [i / (C · f · Et)] × 100 (%) (1) From equation (1), it can be seen that the pulsation rate R decreases as the power supply frequency f increases. I understand. In other words, ripples can be reduced by once converting to high-frequency AC and then rectifying.

Also, by reducing the ripple,
The reason why the spark discharge can be suppressed can be explained as follows. FIG. 11 is a graph showing input and output voltage waveforms when low-frequency low-voltage AC is rectified to high-voltage DC without being once converted to high-frequency low-voltage AC. FIG. 5 is a graph showing input and output voltage waveforms when the voltage is once converted to AC and then rectified to high voltage DC.

These input voltage waveforms are the same as shown in FIGS. 11A and 12A, and have a frequency of 50 Hz and a voltage of 200 V single-phase AC. As shown in FIG. 11 (b), the output voltage waveform when rectified without being converted into a high-frequency AC is a voltage: -100 kV, a ripple rate: 5% (pulsation voltage: 5 kV), and once every 0.1 second. Waveform appears. As shown in FIG. 12 (b), the output voltage waveform once converted to high-frequency AC and then rectified has a voltage of -100 kV and a ripple rate of 0.1% (pulsation voltage of 0.1 kV). When the frequency of the AC pulse is 20 kHz, 200
Zero waveforms appear. In general, the electric dust collector is operated at a high voltage immediately before the shift to the spark discharge, so that it is sensitive to the voltage fluctuation, and tends to immediately shift to the spark discharge even if the voltage is slightly increased.

From FIG. 11, it can be seen that when rectification is performed without once converting to high-frequency AC, the peak voltage due to ripple is high, and
Since it reaches 105 kV, it is understood that the frequency of occurrence of spark discharge increases. Also, it can be seen that when spark discharge occurs, the arc cannot be quickly extinguished due to the long voltage fluctuation cycle. From FIG.
When the current is once converted to a high-frequency AC and then rectified, the peak voltage due to the ripple is low and is -100.1 kV, which indicates that the frequency of spark discharge is low. Also, it can be seen that when a spark discharge occurs, the arc can be quickly extinguished because the voltage fluctuation cycle is short. Therefore, the occurrence of spark discharge can be suppressed by reducing the ripple.

As described above, the occurrence of spark discharge is suppressed by the constant current control of the control device 20, but by reducing the ripple in this manner, the spark discharge suppression effect by the constant current control and the spark by the reduction of the ripple are reduced. Since the discharge suppression effect is added, the spark discharge suppression effect can be further enhanced. Therefore, even when the humidity becomes abnormally high, spark discharge can be further suppressed, and reliability for suppressing spark discharge can be improved.

Further, since the inverter control device 31 controls the switching output of the inverter 33 by high frequency pulse width control, a high voltage output can be obtained from the voltage doubler rectifier 35 with high efficiency, and power saving can be achieved. Also,
Since the output voltage of the power supply 30 is boosted in two stages by the high frequency transformer 34 and the voltage doubler rectifier 35, a high voltage can be easily obtained and the secondary voltage of the high frequency transformer 34 can be set low. it can. The number of windings of the high-frequency transformer 34 becomes smaller as the electromotive force (voltage) becomes lower.
In addition, since the higher the frequency, the lower the number of turns, it is possible to reduce the number of windings of the high frequency transformer 34 by once converting to high frequency alternating current and then rectifying. Therefore, the high-frequency transformer 34 can be reduced in size and weight.

Further, since the high-frequency transformer 34 can be downsized, replacement of the power supply unit is facilitated and maintainability is improved. Further, the configuration of the electric dust collector can be reduced in size, which facilitates installation and carrying, and saves space.

As described above, it is preferable to set the frequency of the high-frequency AC pulse of the inverter 33 to 20 to 35 kHz because, at a frequency of less than 20 kHz, the frequency is once converted to such high-frequency AC and then rectified. This is because the effect cannot be exhibited, and such a high-frequency effect is saturated at a frequency exceeding 35 kHz.

Next, the configuration of the voltage doubler rectifier 35 of this embodiment will be described with reference to FIG. Doubler rectifier 3
Numeral 5 is configured by connecting a capacitor and a diode (rectifier) in parallel, and boosts the secondary voltage of the high-frequency transformer 34 by a plurality of times. In this embodiment, a doubler rectifier called a Cockcroft-Walton circuit as shown in FIG. 13 is used.

In the Cockcroft-Walton circuit, a diode K and a capacitor C connected in parallel are alternately and alternately connected in a plurality of stages (eight stages in the example shown in FIG. 13). Charging starts with the positive half-wave of the secondary voltage of the high-frequency transformer 34,
Diode K1 ignites and charges capacitor C1, and in the next half-wave diode K2 ignites and charges capacitor C2 with the sum of capacitor C1 and the secondary voltage of transformer 34. Hereinafter, similarly, the capacitors C3, C4,..., C8 are successively charged. When the number of capacitors is n and the peak value of the secondary voltage of the transformer 34 is E, the output voltage is n
E (8E in the example of FIG. 13). In this way, the secondary voltage of the high-frequency transformer 34 can be boosted to an integral multiple, so that the output power can be easily boosted to a high voltage. In the Cockcroft-Walton circuit, the voltage applied to each capacitor is twice the secondary voltage of the high-frequency transformer 34, so that a high voltage can be obtained with a capacitor of the same standard. The power supply device 30 of the present embodiment includes:
For example, a voltage of 5 kW or more can be output at 1 kW or more.

FIG. 14 is a diagram showing another embodiment of the voltage doubler rectifier. The doubler rectifier is not limited to the Cockcroft-Walton circuit described above, but may be any as long as it generates a DC voltage that is an integral multiple of the secondary voltage of the transformer using a rectifier and a capacitor, and is shown in FIG. It may be a Delon-Grainacher circuit, a billard circuit shown in FIG. 14B, a Timmelman circuit shown in FIG. 14C, or a Schenkel circuit shown in FIG. There may be.

As described above, the power supply device 30 is provided in the electric precipitator together with the control device 20, and is configured to further enhance the spark discharge suppressing effect by the constant current control of the control device 20 by reducing the ripple. However, as still another embodiment of the present invention, a power supply device having the same configuration as the power supply device 30 may be provided in an electric dust collector in which the control device 20 is not provided. In this case, the set voltage and the set current are set to predetermined values at which no spark discharge occurs.

Although the DC power received by the inverter 33 is supplied by converting the low-voltage AC power from the commercial AC power supply by the rectifier 32, the DC power is directly supplied from the DC power supply such as a battery to the inverter 33. You may comprise so that it may supply. Further, although the voltage and current comparison control circuits 21 and 22 are provided, these circuits may be omitted. Further, although the inverter control device is a pulse width modulator, it is not limited to this, and may be a pulse amplitude modulator,
Other configurations may be used.

[0094]

As described above, according to the first aspect of the present invention, even if a spark discharge occurs, the progress of the spark discharge can be prevented and the normal state can be quickly restored by performing the constant current control. Can be. This also minimizes the reduction in dust collection efficiency due to spark discharge. Further, by suppressing the spark discharge, damage to the electrodes used in the charging unit and the dust collecting unit can be minimized. Further, since the spark discharge detection circuit does not detect the light with a small spark discharge, it is possible to minimize the operation time of a low voltage for preventing the generation of the spark, thereby improving the dust collection efficiency.

According to the second aspect of the present invention, by changing the set current in accordance with the output voltage, the power supply voltage can be maintained substantially at the rated voltage with the optimum set current in accordance with the discharge state. it can.

According to the third aspect of the present invention, at the time of start-up, after the set voltage is set, the set voltage is changed based on the rise of the output voltage after the elapse of a predetermined time, so that the start-up is completed. The set voltage can be set to an optimum voltage according to the state of the discharge space.

According to the present invention, since DC power is once converted to high-frequency AC power and rectification is performed, ripples can be reduced and generation of spark discharge can be suppressed. it can. Thus, the spark discharge suppressing effect due to the reduction of the ripple is added to the spark discharge suppressing effect by the constant current control of the control device, so that the spark discharge suppressing effect can be further enhanced.

According to the fifth aspect of the present invention, since the low-frequency low-voltage AC power can be converted to the low-voltage DC power by the rectifier, a commercial AC power supply can be used as a power source. Can be easily and stably secured.

Further, according to the present invention, the voltage or current comparison control circuit quickly controls the output voltage or output current of the voltage doubler rectifier so as to become the set voltage or the set current. Stability can be improved.

According to the present invention, since the inverter control device is a pulse width modulator, the output voltage or output current of the voltage doubler rectifier can be quickly and accurately adjusted to the set voltage or current. Can control the inverter.

According to the present invention, since the voltage doubler rectifier is a Cockcroft-Walton circuit,
The output voltage can be easily increased to a high voltage. Further, in the Cockcroft-Walton circuit, the voltage applied to each capacitor is twice as high as the secondary voltage of the high-frequency transformer, so that a high voltage can be obtained with a capacitor of the same rating.

According to the ninth aspect of the present invention, since DC is once converted to high-frequency AC and then rectification is performed, ripples can be reduced and generation of spark discharge can be suppressed. . The output voltage of the power supply is
Since the boosting is performed in two stages by the high frequency transformer and the voltage doubler rectifier, a high voltage can be easily obtained and the secondary voltage of the high frequency transformer can be set low. Therefore, the number of windings of the high-frequency transformer can be reduced, and the size and weight of the transformer can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between voltage and current showing constant current control according to the present invention.

FIG. 2 is a time chart showing an output voltage Vo and an output current Io when a spark discharge occurs in constant current control.

FIG. 3 is a diagram showing a configuration of an electric precipitator 1 according to one embodiment of the present invention.

FIG. 4 is a view showing a discharge electrode 7;

FIG. 5 is a block diagram showing a configuration of a power supply device 3 of the electric dust collector 1;

FIG. 6 is a flowchart showing a power control method by the control device 20 at the time of startup.

FIG. 7 is a flowchart illustrating a power control method by the control device 20 during rated operation.

FIG. 8 is a flowchart illustrating another power control method by the control device 20 at the time of startup.

FIG. 9 is a block diagram illustrating a configuration of a power supply device 30.

FIG. 10 is a graph showing temporal transitions of the DC output voltage E1, the AC secondary voltage E0 of the transformer, and the output current Ao of the transformer in the rectifier circuit.

FIG. 11 is a graph showing input and output voltage waveforms when low-frequency low-voltage AC is rectified into high-voltage DC without being once converted to high-frequency low-voltage AC.

FIG. 12 is a graph showing input and output voltage waveforms when low-frequency low-voltage AC is once converted to high-frequency low-voltage AC and then rectified to high-voltage DC.

FIG. 13 is a Cockcroft-Walton circuit diagram.

FIG. 14 is a circuit diagram showing another embodiment of the voltage doubler rectifier circuit.

FIG. 15 is a graph showing a relationship between a voltage and a current in constant voltage control of a conventional electric precipitator.

FIG. 16 is a time chart showing an output voltage Vo and an output current Io when a spark occurs in the constant voltage control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric dust collector 2 Dust collector main body 3, 30 Power supply device 4 Charging part 5 Dust collecting part 6 Counter electrode 7 Discharge electrode 12 Ammeter 13 Voltmeter 20 Controller 21 Current comparison control circuit 22 Voltage comparison control circuit 29 Commercial AC power supply 31 Inverter control Device 32 Rectifier 33 Inverter 34 High-frequency transformer 35 Doubler rectifier

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D054 AA07 BA01 BB06 BC03 CA09 CA16 CA17 CA18 CA19 DA06 5H730 AS00 AS04 BB23 BB43 BB57 CC01 CC28 DD05 EE05 EE06 EE74 EE78 FD01 FD31 FF09 FG07

Claims (9)

[Claims] 1. An electric precipitator for charging a dust by flowing a gas containing the dust between electrodes to which a predetermined rated voltage is applied by a power supply device and collecting the dust by electrostatic force. A voltmeter to detect, an ammeter to detect the output current of the power supply unit, and a set voltage and set current are calculated based on the output voltage detected by the voltmeter, the output current detected by the ammeter, and the preset rated voltage And a control device for inputting to the power supply device. The power supply device controls the output voltage to be the set voltage based on the output voltage detected by the voltmeter and the input set voltage, and detects the output voltage by the ammeter. The control device has a function of controlling the output current to be the set current based on the output current and the input set current, and the control device keeps the set current input to the power supply device at the rated operation constant. In a state of Tsu, electrostatic precipitator, characterized in that as the output current is kept set current and the output voltage is input to the power supply device calculates the set voltage such that the vicinity of the rated voltage. 2. The control device according to claim 1, wherein when the output voltage detected by the voltmeter becomes larger than the vicinity of the rated voltage, the set current is reduced by a reference current having a predetermined value. When it becomes smaller than near the voltage,
The electric dust collector according to claim 1, wherein the set current is increased by the reference current. 3. The control device according to claim 1, wherein the control device sets the set voltage to be equal to or higher than the rated voltage and increases the output current after a predetermined time from inputting the set current to the power supply device. The electric current collector according to claim 1 or 2, wherein the set current is changed based on the following. 4. The power supply device comprises: an inverter for converting low-voltage DC power into high-frequency AC power; a high-frequency transformer connected to the inverter for boosting a high-frequency AC output voltage of the inverter; and a secondary side of the high-frequency transformer. And a voltage doubler rectifier that boosts and rectifies the high-frequency AC output voltage and outputs it to the main body of the electrostatic precipitator, so that the DC output voltage or DC output current of the doubler rectifier becomes the input voltage or current. The electric dust collector according to any one of claims 1 to 3, further comprising an inverter control device that controls the inverter. 5. The dust collector according to claim 4, further comprising a rectifier for converting low-frequency low-voltage AC power into low-voltage DC power and outputting the converted low-voltage DC power to an inverter. 6. A voltage comparison control circuit for determining a difference between an output voltage of the voltage doubler rectifier and a set voltage and sending a signal corresponding to the determined difference to an inverter control device. And a current comparison control circuit for sending a signal corresponding to the obtained difference to an inverter control device. The inverter control device responds to the output of the voltage or current comparison control circuit, and outputs the DC output of the voltage doubler rectifier. The electric dust collector according to claim 4 or 5, wherein the inverter is controlled so that the voltage or the DC output current becomes the set voltage or the set current. 7. The electrostatic precipitator according to claim 4, wherein the inverter control device is a pulse width modulator. 8. The electrostatic precipitator according to claim 4, wherein the voltage doubler rectifier is a Cockcroft-Walton circuit. 9. An inverter for converting low-voltage DC power into high-frequency AC power, a high-frequency transformer connected to the inverter for boosting a high-frequency AC output voltage of the inverter, and a high-frequency transformer connected to a secondary side of the high-frequency transformer. A voltage doubler rectifier that boosts and rectifies the AC output voltage and outputs it to the main body of the electrostatic precipitator, and an inverter that controls the inverter so that the DC output voltage or DC output current of the voltage doubler rectifier becomes the input voltage or current. A power supply device for an electric dust collector, comprising: a control device.