JPH11114448A - Pulse charge type electric precipitator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a proper pulse wave form without repeated sparking while using a rotary spark gap though its rotational speed is low by a method in which charge accumulated in the electrode of a precipitator is recovered temporarily to a recovery capacitor without back-flowing to a powder source. SOLUTION: A timing control means CNT brings a thyristor S into a non- conductive state immediately before the time t1 . At the time t1 , when a switch SW is turned on the side of a fixed contact point T1 , a voltage exchange is carried out between an accumulation capacitor CS and a dust collecting capacitor CEP. At the time t2 , the backflow of current is hindered by a diode D1 . After the time t2 , the current passes only through an LC resonance circuit I2 , and a voltage exchange takes place between the dust collecting capacitor CEP and a recovery capacitor CR. At the time t4 , when the switch SW is turned on the side of a fixed contact point T2 , the charge of CR is transferred to CS. After the time t1 +T3 , the thyristor S1 is brought into a conductive state, and CS is charged to return to the state of the time t1 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic precipitator, and more particularly to a pulse-charge type electric precipitator.

[0002] The pulse charging method of an electric dust collector has a great effect on miniaturization of the dust collector. However, pulse charging devices are generally expensive. In particular, when the dust collector body is of a medium size or less, the cost of the dust collector body is not so high, and the advantage of downsizing the dust collector body is often offset by the disadvantage of increasing the cost of the charging device. Therefore, cost reduction of the pulse charging device is desired.

[0003]

2. Description of the Related Art As a pulse power source for an electric precipitator, those using a semiconductor element such as a thyristor as a switch element and those using a rotary spark gap are known.

FIG. 5 shows a pulse power source using a rotary spark gap according to the prior art. FIG. 5A shows a circuit configuration, and FIG. 5B shows its electrical characteristics.

In FIG. 5A, a DC power supply DC is constituted by a transformer supplied with AC current from an AC power supply and a diode bridge. The anode of the DC power source is grounded, the cathode is connected to one of the stationary electrode of the rotary spark gap RSG ₃ via the impedance Z.

Further, the interconnection point of rotation between the impedance Z spark gap RSG ₃ is connected to one electrode of the storage capacitor C _S. The other electrode of the storage capacitor C _S is grounded.

The rotary spark gap RSG ₃ forms a spark gap between a stationary electrode and a rotary electrode, and the rotary electrode is driven to rotate by a motor M. The other stationary electrode of the rotary spark gap RSG ₃ is connected to one electrode (called discharge electrode) of precipitating capacitor EP through the inductor L _10. Dust collector electrode EP
The other electrode (called a dust collecting electrode) is grounded. The discharge electrode and the dust collection electrode are arranged with a gap therebetween, and a capacitor is formed by the two. Hereinafter, a capacitor formed by the discharge electrode and the dust collecting electrode is referred to as a dust collecting capacitor.

If the voltage applied between the discharge electrode and the dust collecting electrode is equal to or higher than the corona discharge starting voltage of the dust collector electrode EP, corona discharge occurs between both electrodes. Dust charged by corona discharge is collected on the surface of the dust collection electrode by electrostatic force.

When the rotary spark gap RSG ₃ becomes conductive, an LC resonance circuit composed of the storage capacitor C _S , the inductor L ₁₀ and the dust collector electrode EP is formed. By the negative charges accumulated in the storage capacitor C _S, the resonance current is excited in the LC resonance circuit.

FIG. 5B shows the characteristics of the rotary spark gap type pulse power supply shown in FIG. In the figure, the horizontal axis represents time t, and the vertical axis represents a negative voltage generated at the dust collector electrode EP. Period rotary spark gap RSG ₃ is conductive, a current having a natural resonance frequency LC resonant circuit is excited. In the characteristics shown, the oscillation period is several hundred μ.
s, and several periods of vibration occur during this period.

[0011] rotary spark gap RSG ₃ is becomes nonconductive, no longer resonant current flows through the LC resonant circuit, oscillation is stopped. At this time, if the voltage remaining on the dust collector electrode EP is equal to or higher than the corona discharge starting voltage, the dust collector electrode EP
Is reduced by corona discharge, and the negative voltage of the dust collector electrode EP decreases exponentially.

As described above, the rotary spark gap pulse power supply having the circuit configuration shown in FIG. 5A cannot form a single-shot pulse waveform, and vibrates for several cycles until the rotary spark gap becomes non-conductive. Only a multi-pulse waveform can be formed.

The voltage waveform desired for the electrostatic precipitator is a high negative voltage having a single-shot pulse shape and a constant negative voltage referred to as a base voltage in other periods. The voltage waveform shown in FIG. Not as appropriate.

FIG. 5C shows an electronic circuit comprising a thyristor and a diode which can be used in place of the rotary spark gap RSG ₃ of FIG. 5A. This circuit is formed by connecting the thyristor S ₁₀ and diode D ₁₀ in antiparallel. S ₁₀ is actually composed of a number of thyristor element to withstand a high voltage by connecting in series.

Thyristor S_TenIs made conductive, FIG.
As in the case of (A), a resonance current is excited in the LC resonance circuit.
It is. Thyristor S_TenAfter the current flows in the forward direction of
Aether D _TenA current flows in the forward direction of. Diode D_TenTo
Thyristor S while current is flowing_TenTo be non-conductive
And the resonance current flows for only about one cycle and then does not flow
Become.

[0016] However, actually produce things that do not fit rendered non-conductive in the number of thyristor elements constituting a thyristor S ₁₀ can not withstand high voltages as a whole,
Eventually, all of them must be turned on. As a result, a vibration waveform similar to that shown in FIG. 5B actually appears. Thyristors are also more expensive than rotary spark gaps.

FIG. 6 shows an embodiment of the present invention for solving the above problems.
Invented by the inventors and disclosed in Japanese Patent Laid-Open No. 6-343898.
FIG. 1 shows a circuit diagram of an electric precipitator disclosed in a column of an embodiment of the publication.
You. Rotary spark gap RSG_FourDiode in series with
D₁₂Is inserted, and the rotary spark gap RSG_FourAnd die
Aether D₁₂In parallel with the series circuit consisting of ₁₂
Diode D in the opposite direction₁₃Is connected.

[0018] Since a diode D ₁₂ and D ₁₃ are connected in antiparallel, excited resonance current flows through the diode D ₁₂ in the half cycle, the other half cycle through the diode D _13.

[0019] During the half cycle of the resonant current flows through the diode D _13, a current does not flow through the rotary spark gap RSG _4. At this time, an arc plasma occurring in rotary spark gap RSG ₄ disappears. In order to ensure the extinction of the arc plasma, air may be blown to the gap where the arc plasma is generated.

[0020]

With the circuit arrangement of FIG. 6 [0008], it is possible to resonance current is nonconductive the rotary spark gap RSG ₄ at the time of flowing half cycle. However, a forward voltage is generated for re diode D ₁₂ by the vibration due to the LC resonance circuit, rotary spark gap RSG ₄ will be re-ignition.

To prevent re-ignition, a diode D
Before the forward voltage of the second occurs for _12, the rotary electrode of the rotary spark gap RSG ₄ is sufficient angular rotation may be the gap length without sparking. One method for this is to increase the speed of the tip of the rotating electrode to several hundred m / s or more.

It is difficult to manufacture a rotating spark gap that rotates at such a high speed, driving power is increased, and noise increases because the tip of the rotating electrode exceeds the speed of sound.

An object of the present invention is to provide an electric precipitator which can generate a pulse waveform suitable for an electric precipitator without using re-ignition even at a low rotational speed while using an inexpensive rotary spark gap. It is.

[0024]

According to one aspect of the present invention, a DC voltage is intermittently applied, and the storage capacitor includes a storage capacitor charged by the DC voltage, a dust collecting electrode, and a discharge electrode.
A first switch means which forms a current closed circuit together with a dust collecting capacitor in which a corona discharge is generated between the two when a voltage equal to or higher than a corona discharge starting voltage is generated therebetween, and the storage capacitor and the dust collecting capacitor. , A first inductor, and a first diode in series, the first diode flowing a current in a direction to discharge the storage capacitor charged by the DC voltage, and the first diode and the first diode. A first current circuit connected so that the storage capacitor, the first diode, the first inductor, and the dust collection capacitor are arranged in this order, and a current closed circuit together with the dust collection capacitor A recovery capacitor, a second inductor, and a second
Wherein the second diode comprises:
A second current circuit for flowing a current in a direction for discharging the dust collection capacitor charged by discharging the storage capacitor, and a second switch capable of opening and closing, forming a current closed circuit together with the storage capacitor and the recovery capacitor means,
A third current circuit that includes a third inductor and a third diode in series, wherein the third diode flows a current in a direction to discharge the recovery capacitor charged by discharging the dust collection capacitor; Said dust collection capacitor,
Together with the first inductor, a current closed circuit that does not include the first diode and the storage capacitor is configured, and a fourth diode and a protection resistance element are included in series,
When the storage capacitor charged by the DC voltage discharges, the current flows in the current closed circuit including the fourth diode in the same direction as the direction of the current flowing through the first inductor. And a fourth current circuit to which a diode is connected.

When the first switch is closed after the storage capacitor is charged, the electric charge moves from the storage capacitor to the dust collection capacitor via the first current circuit. First
Because the first diode is connected to the current circuit of
The charge flowing into the dust collection capacitor does not flow back to the storage capacitor side. The charge stored in the dust collection capacitor is
To the recovery capacitor via the current circuit. Second
Because the second diode is connected to the current circuit of
The electric charge accumulated in the recovery capacitor does not flow back to the dust collector electrode side.

The first switch is opened during a period when no current flows in the first current circuit. Thereafter, when the second switch is closed, the electric charge stored in the recovery capacitor is returned to the storage capacitor via the third current circuit. Since the third diode is connected to the third current circuit, the charge returned to the storage capacitor does not flow back to the recovery capacitor.

The dust collection capacitor is charged by discharging the storage capacitor, and then the dust collection capacitor is discharged and the recovery capacitor is charged. During the period from when the dust collecting capacitor is charged to when it is discharged, a pulse voltage is generated in the dust collecting capacitor.

When a spark is generated between the dust collecting electrode and the discharge electrode, the storage capacitor is discharged through the first current circuit, and a large current may flow. Due to this large current, the first
Energy is stored in the inductors of the first and second inductors. Energy stored in the first inductor is consumed through the fourth current circuit. This current for energy consumption does not flow through the first diode. Therefore, damage to the first diode due to an overcurrent can be prevented.

[0029]

FIG. 1A shows a circuit configuration of an electric precipitator according to a first embodiment of the present invention. DC power supply DC
Are composed of a transformer and a diode bridge connected to the secondary winding of the transformer. The primary winding of the transformer is connected to the AC power source through the thyristor S _1. Thyristor S ₁ is controlled by the timing control means CNT. The anode of the DC power source is grounded, the cathode is connected through an input resistor element R _i to the power input terminal T _in the electrostatic precipitator circuit PG.

The dust collector electrode EP of the electric dust collector is composed of a discharge electrode and a dust collection electrode, between which gas such as air to be dust-free passes. The dust collecting electrode is grounded, and the discharge electrode is connected to the output terminal T _out of the electric dust collector circuit PG. A capacitor is composed of the dust collection electrode and the discharge electrode. In this specification, this capacitor is referred to as a dust collecting capacitor C _EP .

The electric precipitator circuit PG includes a storage capacitor C _S and a recovery capacitor C _R whose one electrode is grounded, and a current path connecting these capacitors or between these capacitors and the output terminal T _out. It consists of.

Storage capacitor C_SIs the input terminal T_inContact with
Input terminal T _inDC applied to
Charged by voltage. Storage capacitor C_SUngrounded
Movable contact T of switch SW₀It is connected to the.
The switch SW has a movable contact T ₀Two fixed that can conduct with
Contact T₁, T_TwoAnd the timing control means CNT
Is controlled and the contact T₀And T₁The state of conduction between the contacts
T₀And T_TwoThe state of conducting between the contacts, the contact T₀Any solid
One of the states that does not conduct with the constant contact
You.

The fixed contact T _{1 of the} switch SW is connected to the output terminal T via a series circuit of a diode D ₁ and an inductor L _1.
connected to _out . The diode D ₁ is connected to the output terminal T
_The direction in which current flows from _out to the switch SW is defined as the forward direction.

The output terminal T _out is connected to the ungrounded electrode of the recovery capacitor C _R through the series circuit of the inductor L ₂ and the diode D _2. Diode D ₂ is the recovery capacitor C current from _R to the output terminal T _out flow direction as the forward direction.

The non-ground electrode of the recovery capacitor C _R is connected to the fixed contact T ₂ of the switch SW via a series circuit of the inductor L ₃ and the diode D ₃ . Diode D _3, the orientation of the fixed contact T ₂ the current flows to the recovery capacitor C _R and a forward direction.

The non-ground electrode of the storage capacitor C _S and the output terminal T _out are connected by a resistor R. The resistance value of the resistor R is about several tens MΩ, and almost no current flows in a normal operation state. Interconnection point between the inductor L ₁ and the diode D ₁ via a series circuit of a diode D ₄ and the protective resistance element R ₄ is grounded. Diode D ₄ is a direction from the interconnection point between the inductor L ₁ and the diode D ₁ supplying a current to the ground in a forward direction. Under normal operating conditions, since the mutual connection point between the inductor L ₁ and the diode D ₁ is a negative voltage, the diode D ₄ does not conduct.

Switch SW is fixed contact T₁When you pull it to the side,
Storage capacitor C_S, Inductor L ₁And dust collection capacity
TA C_EPLC resonance circuit I consisting of₁Is closed and the fixed contact
T_TwoTo the storage capacitor C_S, Inductor L_Three
And recovery capacitor C_RLC resonance circuit I consisting of_ThreeIs closed
Is done. Also, the dust collection capacitor C_EP, Inductor L _Two
And recovery capacitor C_RLC resonance circuit I_TwoIs shaped
Has been established.

That is, the diode D₁And inductor L
₁The series circuit of the switch SW and the storage capacitor C_S
And dust collection capacitor C_EPWith current closed circuit I₁Make up
You. Diode L₁Was charged by DC power supply DC
Storage capacitor C_SA current in the direction in which is discharged. This
Dust collection capacitor C_EPIs charged. Ma
The diode D₁And inductor L₁Is the storage capacity
TA C_S, Diode D ₁, Inductor L₁, Dust collection capacity
Sita C_EPAre connected so that they are arranged in this order.

The series circuit of the recovery capacitor C _R , the inductor L ₂ and the diode D ₂ forms a current closing circuit I ₂ together with the dust collection capacitor C _EP . The diode D ₂ allows a current to flow in a direction to discharge the dust collection capacitor C _EP charged by discharging the storage capacitor C _S. Recovery capacitor C _R is charged by the discharge current.

The series circuit of the switch SW and the inductor L ₃ and a diode D ₃ constitute a current closed circuit I ₃ with the storage capacitor C _S and the recovery capacitor C _R. Diode D ₃ flows the current in a direction to discharge the recovery capacitor C _R, which is charged by the discharge of the dust-collecting capacitor C _EP.
Storage capacitor C _S is recharged by the discharge current.

The series circuit of the diode D ₄ and the protection resistance element R ₄ constitutes a current closing circuit I ₄ together with the dust collecting capacitor C _EP and the inductor L ₁ . The current closed circuit I _4, does not include the diode D ₁ and the storage capacitor C _S. The polarity of the diode D ₄ is, current through the inductor L ₁ is set to flow branches to the diode D ₁ and the diode D _4.

Hereinafter, a case where the respective capacitances of the storage capacitor C _S , the recovery capacitor C _R, and the dust collection capacitor C _EP are substantially equal will be described. Inductance of the inductor L ₁ is, for example half period T ₁ of the resonance frequency of the LC resonance circuit I ₁ is selected to be about 10 [mu] s. That is,

[0043]

T ₁ = π (L ₁ C _S C _EP / (C _S + C _EP ))
^1/2 = about 10 μs.

The inductance of the inductor L ₂ is, for example, half cycle T ₂ of the resonance frequency of the LC resonance circuit I ₂ of about 10
0 μs. That is,

[0045]

T ₂ = π (L ₂ C _EP C _R / (C _EP + C _R ))
^1/2 = about 100 μs. In this case, L ₂ is about 100 times that of L _1.

Next, referring to FIG.
The operation of the circuit of FIG. FIG. 1B shows a time change of the voltage of the non-ground electrode of each capacitor of the electric precipitator circuit PG of FIG. 1A. The horizontal axis represents time, and the vertical axis represents negative voltage. Curves V _S , V _EP , and V _R indicate voltages between the electrodes of the storage capacitor C _S , the dust collection capacitor C _EP , and the recovery capacitor C _R , respectively.

Prior to time t ₁ , switch SW is off. The storage capacitor _CS is a DC power supply D
The battery is charged up to the output voltage of C, and the voltage V _S has reached the initial value V _SO . The absolute value of this voltage is sufficiently higher than the corona discharge starting voltage of the dust collector electrode EP. At this time, negative charges are accumulated in the dust collection capacitor C _EP by the operation until time t ₁ . Since this negative charge is lost by corona discharge, in a steady state, the voltage V _EP is almost equal to the corona discharge starting voltage, and has an initial value V _EPO .

When the voltage V _R becomes higher than the voltage V _EP (the absolute value becomes smaller), the diode D ₂ conducts, and a current flows from the recovery capacitor C _R to the dust collection capacitor C _EP . Voltage V _R is slightly lower than voltage V _EP (absolute value is large) and has initial value V _RO .

The timing control means CNT brings the thyristor S ₁ into a non-conductive state immediately before the time t ₁ .

[0050] The timing control means at time t ₁ CN
T is defeat the switch SW to the fixed contact T ₁ side. Closed LC resonance circuit I _1, forward current of the diode D ₁ flows. That is, the electric charge stored in the storage capacitor C _S flows into the dust collection capacitor C _EP . Therefore, the voltage V _S
Decreases, and the absolute value of the voltage V _EP increases. That is, voltage exchange is performed between the storage capacitor C _S and the dust collection capacitor C _EP . Since the capacitance of the storage capacitor C _S and the dust collecting capacitor C _EP is approximately equal, the amount of increase in the absolute value of the voltage V _EP is approximately equal to the decrease of the absolute value of the voltage V _S.

[0051] When there is no energy loss due to electrical resistance, LC resonant circuit at the point of time t ₂ to a half period T ₁ is passed the resonance frequency of the I _1, the absolute value of the voltage V _EP voltage V _S
To the initial value V _EPO, and the absolute value of the voltage V _EP
It increases to the initial value V _{SO of S.} Although current At time t ₂ is about to backflow, reverse current for the diode D ₁ is inserted does not flow.

When the absolute value of the voltage V _EP becomes larger than the absolute value of the voltage V _R , the diode D ₂ conducts, so that a part of the negative charges accumulated in the dust collecting capacitor C _EP flows into the collecting capacitor C _R. . However, since the half cycle T ₂ of the resonance frequency of the LC resonance circuit I ₂ is about 10 times the half cycle T ₁ of the LC resonance circuit I ₁ , the rise time of the resonance current excited by the LC resonance circuit I ₂ becomes enough long compared to the time T _1. Therefore, during the period from time t _{1 to} time t ₂ , the LC resonance circuit I
The change in the voltage V _EP due to the current flowing through ₂ is very small.

After time t ₂ , the current in the LC resonance circuit I ₁ stops flowing, the current flows only in the LC resonance circuit I ₂ ,
Negative charge accumulated in the dust collecting capacitor C _EP is moved to the recovery capacitor C _R. Therefore, the absolute value decreases the voltage V _EP, the absolute value of the voltage V _R is increased. That is, voltage exchange is performed between the dust collection capacitor C _EP and the collection capacitor C _R. Since the capacitances of the dust collection capacitor C _EP and the collection capacitor C _R are substantially equal, the amount of decrease in the absolute value of the voltage V _EP is substantially equal to the amount of increase in the absolute value of the voltage V _R.

[0054] When there is no energy loss due to electrical resistance, the absolute value of the voltage V _EP is decreased to the initial value V _RO of the voltage V _R, the absolute value of the voltage V _R is increased to the initial value V _SO voltage V _S . The half period T ₂ is the time t ₃ has elapsed, since a reverse bias is generated in the diode D _2, a current does not flow. At this point, the absolute value of voltage V _EP is equal to its initial value V
Since the drops to voltage V _RO close to the _EPO, pulse waveform falling edge of the voltage V _EP becomes sharp, the base voltage becomes almost flat.

[0055] time t ₂ subsequent to the timing control means CNT
Returns the switch SW to the neutral position. At this time, almost no current flows through the switch SW.
W can be easily turned off.

After time t ₁ , thyristor S ₁ is in a non-conductive state, so that after time t ₂ , voltage V _S remains substantially at initial value _VEPO . The time t ₃ after, for diodes D _1, D ₂ is nonconductive both the voltage V _EP and V _R is substantially maintains a constant value.

At time t ₄ , the timing control means CN
T is defeat the switch SW to the fixed contact T ₂ side. The LC resonance circuit I ₃ is closed, and a forward current of the diode D ₃ flows,
The charge stored in the recovery capacitor C _R moves to the storage capacitor C _S. Therefore, the absolute value of the voltage V _R decreases and the absolute value of the voltage V _S increases. That is, voltage exchange is performed between the recovery capacitor C _R and the storage capacitor C _S.

The storage capacitor C _S and the recovery capacitor C _R
And the voltage V _S remains at a value close to the initial value V _EPO after time t ₂ , so that if there is no loss due to electrical resistance, the absolute value of the voltage V _R is close to the initial value V _EPO. To decrease. This value becomes the initial value V _RO of the next pulse. The absolute value of the voltage V _S is increased substantially to the initial value V _SO.

After time t ₁ , the absolute value of the voltage V _EP is gradually reduced by the corona discharge between the dust collector electrodes EP, superimposed on the above-described voltage change. Therefore, at time t ₄ +
When sufficient time has elapsed from T _3, the voltage V _EP is approximately equal to the corona discharge starting voltage.

After time t ₄ + T ₃ , the timing control means CNT makes the thyristor S ₁ conductive. When the absolute value of the voltage V _S is lower than the initial value V _SO ,
, The storage capacitor C _S is charged, and the voltage V _S recovers to the initial value V _SO . Thus, the voltages V _S , V _EP
And V _R return to the same state as at time t ₁ .

The voltage V _EP shown in FIG. 1 (B) has a base voltage that is substantially equal to the corona discharge starting voltage, and has a time t _1.
For a period of ~t ₃ having a negative waveform pulse voltage is superimposed. That is, it is possible to intermittently generate a single-pulse voltage that is almost ideal for the pulse-charged electric precipitator.

Next, a case where a spark occurs inside the dust collector electrode EP, that is, a case where the dust collecting capacitor C _EP is short-circuited will be described.

FIG. 2A shows an equivalent circuit diagram when the dust collecting capacitor C _EP is short-circuited. The diode bridge of the DC power supply shown in FIG.
It is represented by B. 2 (B), 2 (C), and 2
(D) shows an inductor L ₁ , a diode D ₁ ,
And showing the time variation of the current flowing through the diode D _4.

If a spark occurs when the contacts T ₀ and T _{1 of the} switch SW are conducting, the short-circuited dust collecting capacitor C _EP , inductor L ₁ , diode D ₁ , switch SW and storage capacitor C _S LC formed
Resonance circuit I ₁ is closed. Therefore, the discharge current of the storage capacitor C _S flows through the LC resonance circuit I _1. At this time, the thyristor S ₁ shown in FIG. 1 (A) is in a non-conductive state.

As shown in FIGS. 2B and 2C,
At the spark occurrence time u ₀ , a resonance current according to the natural oscillation of the LC resonance circuit I ₁ starts flowing through the inductor L ₁ and the diode D ₁ . At time u ₁ after 1/4 cycle of the natural vibration, resonance current showing a maximum value. Voltage between both electrodes of the storage capacitor C _S at this time is 0. In other words, the potential of the interconnection point between the inductor L ₁ and the diode D ₁ is also zero.

[0066] Time u ₀ electrical energy (1/2) accumulated in the storage capacitor C _S in C _S v _SO ² is the electric energy at the time u ₁ is accumulated in the inductor L ₁ (1/2) L _This means that it has been converted to ₁ i ₀ ² .
Here, v _SO is the storage capacitor C _{S at} time u ₀ .
Represents the voltage between both electrodes, and i ₀ represents the current flowing through the inductor L ₁ at time u ₁ . This current i
₀ usually reaches several hundred amps. Time u ₁ and later, the inductor L ₁ acts as a current source.

After time u ₁ , when the potential at the interconnection point between diode D ₁ and inductor L ₁ becomes negative, diode D 1
₄ is rendered conductive, current flows through the current closed circuit I _4. Therefore, as shown in FIG. 2 (D), a current starts to flow through the Daido D ₄ at time u _1. The current flowing through the current closing circuit I ₄ decreases exponentially with a time constant of approximately L ₁ / R ₄ .
Normally, each element is selected so that 1 / R ₄ C _S >> R ₄ / L ₁ , so that the current flowing through the current closing circuit I ₄ does not become oscillating. Some current is diode D
_The storage capacitor is charged to the opposite polarity through ₁ and flows through the diode bridge DB.

When there is no series circuit of the diode D ₄ and the resistance element R ₄ , the current using the inductor L ₁ as a current source is
Together through the series circuit of the input resistor element R _i and the diode bridge DB through the diode D _1, to charge the storage capacitor C _S in the opposite polarity. Therefore, a large current will flow for a long time diode D ₁ and the diode bridge DB. Therefore, it must be used large allowable current as the diode D ₁ and the diode bridge DB.

On the other hand, when the diode D ₄ and the resistor R ₄ are inserted, a current branches and flows into a series circuit including the diode D ₄ and the resistor R ₄ . Since the current closed circuit I ₄ does not include the diode D _1, the current flowing through the diode D ₁ is rapidly reduced as shown in FIG. 2 (C). Similarly, the current flowing through the diode bridge DB also decreases. As shown in FIG. 2 (B), the current flowing through the inductor L ₁ is the sum of the current flowing through the current and the diode D ₄ through the diode D _1.

The diode D ₁ and the diode bridge D
Since the current flowing through B can be reduced, the diodes D ₁ and the diode bridge DB having small allowable currents can be used, and the cost can be reduced.

[0071] Time u ₁ after the ratio of the current flowing through the current and the diode D ₄ through the diode bridge DB is approximately equal to the inverse ratio of the resistance values of the input resistance element R _i and the protective resistance element R _4. Therefore, in order to reduce the current through the diode bridge DB may be reducing the resistance value of the protective resistance element R ₄ to the resistance value of the input resistance element R _i. Specifically, it is preferable that the resistance value of the protective resistance element R ₄ and 1/100 of the resistance value of the input resistance element R _i.

The resistance element R shown in FIG. 1A restores the voltage _VEP to a normal base voltage within a few seconds after a spark is generated inside the dust collector electrode EP.

FIG. 3 shows a case where a rotary spark gap is used as the switch SW of FIG. Rotary spark gap RSG ₁ has substantially a rectangular four stationary electrodes ST ₁ ~ST ₄ arranged at vertexes of the two rotary electrodes RT _1, RT _2. Stationary electrode ST _1, ST ₂ are both connected to the contact T ₀ in FIG. 1 (A), the stationary electrode ST _3,
ST ₄ is connected to the fixed contacts T ₁ and T ₂ in FIG. The two rotating electrodes RT ₁ and RT ₂ are connected to each other by a rod-shaped member 21 and are electrically short-circuited, and the center thereof is attached to the rotating shaft 20. The rotation shaft 20 is
It is arranged at the center of a rectangle having _four stationary electrodes ST _{1 to} ST ₄ as vertices.

Rotating electrode RT₁, RT_TwoIs the rotation of the rotating shaft 20
When the electrode rotates and approaches the stationary electrode, it is released into the gap between them.
Electricity is generated and the electrodes are conducted. For example, the rotating electrode RT₁,
RT _TwoAre stationary electrodes ST₁, ST_ThreeWhen approaching
Contact T₀And T₁The connection is conducted. This is shown in FIG.
Switch SW is fixed contact T₁In a state of falling to the side
Corresponding.

From this state, when the rotating electrodes RT ₁ and RT ₂ rotate clockwise and approach the stationary electrodes ST ₄ and ST ₂ ,
The contacts T ₀ and T ₂ are turned on. This switch SW corresponds to the state lying in the fixed contact T ₂ side in FIG. 1 (A).

A fan-shaped light shielding plate 22 that is rotationally symmetric about the rotation shaft 20 is attached to the rod-shaped member 21. A light source and a rotating electrode position detecting means 23 for receiving light emitted from the light source and generating and outputting a light detection signal are arranged near the rotating shaft 20. The light-shielding plate 22 includes a rotating electrode R
It rotates together with T ₁ , RT ₂ and the rod-shaped member 21 to block the optical path of the rotating electrode position detecting means 23.

The light shielding plate 22 is arranged so as to shield the optical path of the rotating electrode position detecting means 23 before time t ₁ in FIG. 1B, and to release the light shielding after time t ₄ + T _3. I have. That is, the light shielding plate 22 is connected to the rotating electrodes RT ₁ and RT
₂ is shielding the light path of the rotary electrode position detecting means 23 before the spark is generated between approaching the stationary electrode ST _1, ST ₃ electrodes, rotary electrode RT _1, RT ₂ stationary electrode S
Approaching the T _4, ST ₂ to release the light blocking after the lapse of the time T ₃ from the point of generating a spark.

The output signal of the rotating electrode position detecting means 23 is input to the timing control means CNT shown in FIG. The timing control means CNT includes a rotating electrode position detecting means 23.
Period in which the optical path of is blinded to the thyristors S ₁ in a non-conductive state.

In the above embodiment, the storage capacitor C_S, Times
Capacitor C_RAnd dust collecting capacitor C_EPAre approximately equal
The case of having the capacitance has been described. But the reality
Has a dust collection capacitor C_EPPrecisely Predicts the Electrostatic Capacitance
It is difficult. Therefore, the storage capacitor C_SAnd recovery
Capacitor C_RThe capacitance of the dust collection capacitor C _EP
It is not easy to make the configuration almost equal to the capacitance of
Not easy. Ensure normal operation even in such cases
In order to be safe,_EP<C_RDesigned to be
Is preferred. Further, C_EP<C_SSo that
It is preferable to design.

FIG. 4A shows a circuit configuration of an electric precipitator according to a second embodiment of the present invention, and FIG.
(A) shows a time change of the voltage of each capacitor of the electrostatic precipitator.

The circuit PG for the electric precipitator shown in FIG.
It is Figure 1 (A) an LC resonance circuit I ₃ of the electrostatic precipitator circuit PG shown in removed is constructed by connecting a resistive element R ₂ in parallel with the diode D ₂ instead. Since having no LC resonance circuit I _3, rotary spark gap RS having two stationary electrodes in place of the switch SW in FIG. 1 (A)
G ₂ is used. Rotary spark gap RSG ₂
Is equivalent to excluding the stationary electrode ST ₂ and ST ₄ the rotary spark gap RSG ₁ shown in FIG. Other structures are the same as those of the electric dust collector circuit shown in FIG.

Time t in FIG. 4B₁Immediately after the voltage V_EPof
Absolute value is voltage V_RTime since the absolute value of
t_ThreeThe period until the diode D shown in FIG._TwoIs conductive
doing. For this reason, in FIG._Twoof
Voltage V with or without_S, V _EPAnd V_RFigure 1 (B)
Time t₁~ T_ThreeShows a change similar to that of the period.

After the time t ₃ , when a reverse bias is generated in the diode D ₂ , the negative charge of the recovery capacitor C _R gradually leaks to the dust collector electrode EP through the resistor R ₂ and is consumed by corona discharge of the dust collector electrode EP. . Therefore, the absolute value of the voltage V _R gradually decreases. That is, after the voltage V _EP shows a single pulse waveform in a period corresponding to the times t _{1 to} t ₃ in FIG. 4B, the absolute values of the base voltages of the voltages V _R and V _EP slowly decrease, and this is the next time. Pulse initial value V _RO ,
V _EPO .

When the circuit PG for the electric precipitator shown in FIG. 4A is employed, the voltage generated at the precipitator electrode cannot be an ideal waveform in which a single pulse is superimposed on the corona discharge starting voltage, but it is less. Reignition of the rotary spark gap can be prevented by the number of parts.

[0085] Also in the second embodiment, as in the case of the first embodiment shown in FIG. 1, the diode bridge diodes D ₁ and the DC power source when the spark occurs in the precipitator electrodes EP The flowing current can be reduced.

In the first and second embodiments, FIG.
In (B), the half cycle T ₁ is about 10 μs and T ₂ is about 10 μs.
Although the case of 0 μs has been described, other times may be used. However, in order to increase the pulse height of the voltage V _EP sufficient, the half period T ₂ sufficient longer than the half period T _1, for example 1
It is preferable to set it to 0 times or more.

Time T₁0.1 μs, time T_Two1 μs
To a short length, a long streamer
Gas is likely to be generated and chemically active
O radicals, OH radicals, and the like are easily generated. these
In the gas due to the radicals_TwoIs oxidized to H_TwoSO
_Fourbecome. NH in collected gas_ThreeAnd inject H_TwoSO _Four
To neutralize (NH_Four)_TwoSO_FourCan be collected as
Wear. Thus, by driving relatively short pulses,
Thus, it can be used as a desulfurization device.

Further, since H ₂ SO ₄ acts to lower the electrical resistance of the collected dust, the reverse ionization phenomenon caused by the high-resistance dust film adhered to the dust collector electrode surface can be suppressed.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0090]

As described above, according to the present invention,
The circuit for applying the pulse voltage can be easily opened after the single-pulse voltage is applied to the dust collector electrode by temporarily collecting the charge accumulated in the dust collector electrode to the power supply side without returning to the power supply side to the collection capacitor. . This makes it possible to apply a voltage having a waveform close to the ideal waveform to the dust collector electrode.

Further, since a bypass circuit for passing an abnormal current when a spark occurs in the dust collector electrode is provided,
The destruction of the electric element due to the abnormal current can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of an electric precipitator according to a first embodiment, and a graph showing a time change of a voltage generated in each capacitor of the electric precipitator.

FIG. 2 is an equivalent circuit diagram when a spark occurs in a dust collector electrode of the electric dust collector shown in FIG. 1, and a graph showing a time change of a current flowing through each element of the equivalent circuit.

3 is a diagram showing another configuration example of the switch of the electric dust collector circuit shown in FIG. 1. FIG.

FIG. 4 is a diagram showing a circuit configuration of an electric precipitator according to a second embodiment, and a graph showing a time change of a voltage generated in each capacitor of the electric precipitator.

FIG. 5 is a diagram showing a circuit for an electric precipitator according to a conventional example, a peripheral circuit thereof, and a circuit configuration of a precipitator electrode, a graph showing a time change of a voltage of the electric precipitator circuit, and a rotating spark gap portion of the electric precipitator circuit; FIG. 3 is a diagram showing an example of the configuration.

FIG. 6 is a diagram showing a conventional circuit for an electric precipitator, a peripheral circuit thereof, and a circuit configuration of a precipitator electrode.

[Explanation of symbols]

 Reference Signs List 20 rotating shaft 21 rod-shaped member 22 light shielding plate 23 rotating electrode position detecting means L inductor C capacitor RSG rotating spark gap D diode DB diode bridge R resistance DC DC power supply EP dust collector electrode S thyristor CNT timing control means SW switch PG circuit for electric dust collector RT Rotating electrode ST Stationary electrode

Claims (3)

[Claims] A DC voltage is intermittently applied, comprising a storage capacitor charged by the DC voltage, a dust collecting electrode, and a discharge electrode. A dust-collecting capacitor in which a corona discharge occurs in the current collector; a current-closing circuit comprising the storage capacitor and the dust-collecting capacitor;
And a first diode in series, the first diode flowing a current in a direction to discharge the storage capacitor charged by the DC voltage, and the first diode and the first inductor A first current circuit connected so as to be arranged in the order of the storage capacitor, the first diode, the first inductor, and the dust collection capacitor; A second current circuit including a capacitor, a second inductor, and a second diode in series, wherein the second diode flows a current in a direction to discharge the dust collection capacitor charged by discharging the storage capacitor. And a second switch means which forms a current closed circuit together with the storage capacitor and the recovery capacitor and is openable and closable;
A third current circuit, which includes an inductor and a third diode in series, the third diode flowing a current in a direction to discharge the recovery capacitor charged by discharging the dust collection capacitor; A dust capacitor, together with the first inductor,
Forming a current closed circuit that does not include the first diode and the storage capacitor, includes a fourth diode and a protection resistor element in series, and a current flowing through the first inductor is connected to the first diode and the fourth diode. And a fourth current circuit to which the fourth diode is connected so as to branch and flow to the diode. 2. The storage capacitor further includes an input resistance element inserted in a charging circuit charged by the DC power supply, wherein a resistance value of the protection resistance element is smaller than a resistance value of the input resistance element. 2. The pulse-charged electric precipitator according to 1. 3. The pulse charged type electrostatic precipitator according to claim 2, wherein a resistance value of the protection resistance element is 1/100 or less of the input resistance element.