JPH11128771A - Pulse power supply device for electric dust collector and operating method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the crossectional area of a magnetic core in a pulse transformer by detecting the magnetic density of the transformer due to the excitation of ripple voltage between a dust collection electrode and an electric discharge electrode and applying a control signal to a power control switch on a high voltage pulse generation circuit for making the switch when the magnetic flux density is reduced from a maximum value by a specified value. SOLUTION: A power control switch S2 on a high voltage pulse generation circuit 5 is turned ON by a control signal from a control part 5B, and in this case, the magnetic flux density of a magnetic core in a pulse transformer PT is detected, in terms of voltage, by voltage detection resistor R1 and R2. Further, the detected voltage is integrated by an integrating circuit IN to obtain a voltage time product corresponding to the actual magnetic flux density. Then, in a comparator CP, a voltage signal from a subtraction circuit SS is compared to a voltage corresponding to the magnetic flux density of the magnetic core in the pulse transformer PT. When the latter is lower than the former, an output signal is sent to a control signal generator CC. The control generator CC receives the output signal and supplies a control signal to the power control switch S2 so that the switch S2 is turned ON.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse power supply used in a pulse-charged electric precipitator and an operation method thereof, and more particularly to a timing of applying a high voltage pulse between a precipitating electrode and a discharge electrode.

[0002]

2. Description of the Related Art A pulse charging type electric dust collector uses a dust collection chamber having a dust collection electrode and a discharge electrode as a capacitor, and uses a LC series resonance with a resonance inductance or a leakage inductance of a pulse transformer to transmit a high voltage pulse. It is superimposed on the DC high voltage and applied between the dust collection electrode and the discharge electrode. Such a pulse-charged electric precipitator can increase the dust collection efficiency against the reverse ionization action of high-resistance dust, and has high efficiency because the resonance energy is recovered as a feedback current by the power supply.

A power supply device for such a pulse-charged electric collector is the same as a conventional device except for a control unit 5B for generating a high-voltage pulse in FIG. 1 for explaining an embodiment of the present invention. ), The high voltage pulse is superimposed on the DC high voltage via the pulse transformer PT and the discharge electrode 2A and the dust collection electrode are superimposed.
Charge between 2B. Since the higher the ripple voltage, the higher the dust collection efficiency, a DC voltage with a large ripple voltage is applied between the dust collection electrode and the discharge electrode, and corona discharge occurs between the discharge electrode 2A and the dust collection electrode 2B. Therefore, the voltage between these electrodes includes a considerably large ripple voltage. Therefore, a ripple voltage is applied to the secondary winding of the pulse transformer PT via the DC blocking capacitor C2, so that a large voltage in which the ripple voltage and the high-voltage pulse are superimposed is applied to the pulse transformer PT. Is generated.

Here, in FIG. 1, a DC high-voltage power supply 1
Assuming an average output voltage of 50 kV, a ripple voltage of 5 kV (0 V peak), a ripple frequency of 100 Hz, a pulse width of 100 μs (width at half the peak value time), and a pulse height of 60 kV, ripple Voltage is sinusoidal, pulse voltage is (1-
Approximate to the COS waveform, the amount of magnetic flux (voltage-time product VT) is a combination of the ripple voltage component (5 kV x 2 x 10 ms / 3.14 = 31.8 Vs) and the high voltage pulse voltage component (60 kV x 100 μs = 6 Vs) become.

Here, when a grain-oriented silicon steel sheet is used for the magnetic core of the pulse transformer PT, the frequency component (5
kHz), the change in magnetic flux density of the high voltage pulse component is selected to be 0.6 Tesla. At this time, the amount of change in the magnetic flux density of the ripple component is 3.18 Tesla (the maximum magnetic flux density is 1.59 Tesla).

When a high-voltage pulse is generated irrespective of the phase of the commercial power supply of the DC high-voltage power supply 1, in the worst case, the magnetic flux density of the selected core of the pulse transformer PT becomes 2.19 Tesla and saturates. In order to limit the maximum magnetic flux density to about 1.6 Tesla or less, which is equal to the maximum magnetic flux density of the ripple component, the cross-sectional area of the core of the pulse transformer PT must be increased by 1.4 times. Is not preferred.

[0007]

As can be seen from the above, since a pulse transformer is applied with a voltage obtained by superimposing a ripple voltage and a high-voltage pulse, the magnetic flux of the core of the pulse transformer is equal to the sum of the two voltages. Determined by the voltage, the pulse transformer had to be large.

In the present invention, after the magnetic flux density of the pulse transformer changes due to the ripple voltage and reaches a magnetic flux level at which the magnetic flux density decreases from the maximum value to the magnetic flux density increase substantially corresponding to the magnetic flux density increase by the high-voltage pulse, First, a high voltage pulse is applied between the dust collecting electrode and the discharge electrode during a period during which the bidirectional power control switch is not turned on for a certain period of time, that is, a period immediately before the dead time ends. Another feature is that a high voltage pulse is applied between the dust collecting electrode and the discharge electrode immediately before the end of the dead time. With this operation, the actual maximum value of the magnetic flux density of the pulse transformer does not become larger than the maximum value due to the ripple voltage in a state where the high voltage pulse is not applied.

The present invention reduces the size of the pulse transformer by appropriately setting the generation timing of the high voltage pulse so that the high voltage pulse is generated when the magnetic flux density of the pulse transformer becomes lower than a certain level. The main purpose is to

[0010]

Means for Solving the Problems In order to solve the above problems, the invention according to claim 1 controls a bidirectional power control switch for controlling AC power and the operation of the bidirectional power control switch. A first DC high-voltage power supply, a second DC high-voltage power supply, and a second DC high-voltage power supply that includes a control unit, a step-up transformer, and a high-voltage rectifier circuit and that applies a DC high voltage between a dust collection electrode and a discharge electrode; A high-voltage pulse generation circuit for pulsing a high-voltage DC from a high-voltage DC power supply, wherein the high-voltage pulse generation circuit superimposes a high-voltage pulse on the high-voltage DC from the first DC high-voltage power supply. A pulse power supply for an electric precipitator applied between the dust collecting electrode and the discharge electrode, wherein a magnetic flux density detector for detecting a magnetic flux density of the transformer by exciting a ripple voltage between the dust collecting electrode and the discharge electrode; The magnetic flux density of the vessel is determined from the maximum value A magnetic flux density setting level detector for generating a detection signal when the value decreases, a detection signal from the magnetic flux density setting level detector, receiving a detection signal from the magnetic flux density setting level detector, and applying a control signal to a power control switch of the high voltage pulse generation circuit to conduct the signal. A pulse power supply device for an electric precipitator, comprising: a control signal generator.

[0011] In order to solve the above-described problem, according to a second aspect of the present invention, in the first aspect, the magnetic flux density detector includes a voltage applied to a winding of the transformer and a time of each cycle. A magnetic flux density setting level detector, wherein the magnetic flux density setting level detector peak-holds an integrated value of the integration circuit, a setting voltage source that presents a voltage corresponding to a setting magnetic flux, and the peak holding circuit And a comparator for comparing a voltage signal from the subtraction circuit with an integration value of the integration circuit, the pulse power supply for an electrostatic precipitator, comprising: To provide.

[0012] In order to solve the above-described problem, the invention according to claim 3 provides a bidirectional power control switch for controlling AC power with a dead time that does not turn on for a fixed period in each cycle, and a bidirectional power control switch for the bidirectional power control switch. A first DC high-voltage power supply, a second DC high-voltage power supply, including a control unit for controlling operation, a step-up transformer, and a high-voltage rectifier circuit for applying a DC high voltage between the dust collection electrode and the discharge electrode; A high-voltage pulse generating circuit for pulsing a DC high voltage from the second high-voltage power supply, wherein the high-voltage pulse generating circuit superimposes a high-voltage pulse on the DC high voltage from the first DC high-voltage power supply The method for operating a pulse power supply for an electric precipitator applied between the dust collection electrode and the discharge electrode in such a manner that the predetermined value is determined from the maximum value of the magnetic flux density of the transformer by exciting the ripple voltage between the dust collection electrode and the discharge electrode. Value decreased A method of operating a pulse power supply for an electric dust collector, wherein the high voltage pulse is applied between the dust collecting electrode and the discharge electrode during a period from the time of a bell to immediately before the dead time of the bidirectional power control switch ends. Is provided.

[0013] In order to solve the above-described problem, the invention according to claim 4 provides a bidirectional power control switch that controls AC power with a dead time that does not turn on for a predetermined period in each cycle, and a bidirectional power control switch for the bidirectional power control switch. A first DC high-voltage power supply, a second DC high-voltage power supply, including a control unit for controlling operation, a step-up transformer, and a high-voltage rectifier circuit for applying a DC high voltage between the dust collection electrode and the discharge electrode; A high-voltage pulse generating circuit for pulsing the high-voltage DC from the second high-voltage power supply, wherein the high-voltage pulse generating circuit converts the high-voltage pulse to a high-voltage DC from the first high-voltage DC power supply. In the method of operating a pulse power supply for an electric precipitator applied between the dust collecting electrode and the discharge electrode so as to overlap, the high voltage pulse is collected at a set time before a dead time of the bidirectional power control switch ends. The present invention provides a method for operating a pulse power supply device for an electrostatic precipitator, wherein a pulse voltage is applied between a pole and a discharge electrode.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and Examples of the Invention A pulse power supply for an electric precipitator will be described with reference to FIG.
1A is a main circuit part of the first DC high-voltage power supply 1, and is a bidirectional power control comprising an AC input terminals U and V connected to a commercial AC power supply and a power control switch such as a thyristor connected in anti-parallel. It comprises a switch S1, a current limiting inductance L1, a step-up transformer T, and a full-wave rectifier circuit Re connected to the secondary winding of the step-up transformer T. 1B is a normal control unit that controls the bidirectional power control switch S1 of the main circuit unit 1A of the DC high-voltage power supply 1, detects input voltage and output voltage, and controls conduction of the bidirectional power control switch S1. I do. 1st DC high voltage power supply 1
Is a normal circuit.

Here, the DC high-voltage power supply 1 applies a predetermined voltage controlled by the bidirectional power control switch S 1 to the dust collection chamber 2.
Is applied between the discharge electrode 2A and the dust collection electrode 2B, but this voltage is not smoothed, and a corona discharge current flows between the discharge electrode 2A and the dust collection electrode 2B of the dust collection chamber 2. For this reason, the voltage between the discharge electrode 2A and the dust collection electrode 2B of the dust collection chamber 2 includes a considerably large ripple voltage.

Reference numeral 3 denotes a second high-voltage power supply that supplies power to the high-voltage pulse generating circuit 5 through a current-limiting impedance 4 which is usually an inductor. High voltage pulse generation circuit
5 is composed of a main circuit section 5A and a control section 5B.The main circuit section 5A is an energy storage capacitor C1, which also acts as a resonance capacitor, and a power control switch in which a semiconductor switch such as a thyristor and a diode are connected in anti-parallel. S2, resonance inductor L2, pulse transformer P for boosting pulse voltage
T and DC blocking capacitor C2.
The main circuit section 5A has a normal circuit configuration.

The control unit 5B of the high voltage pulse generation circuit 5
An integration circuit IN for integrating the detected voltage of the primary winding voltage of the pulse transformer PT with time, a peak hold circuit PH for detecting a peak value of the integrated value, and a conventional control signal generation circuit CC.
A set voltage source RP having a predetermined voltage, a subtraction circuit SS for outputting a voltage signal obtained by subtracting the set voltage from the peak voltage of the peak hold circuit PH, an integration voltage from the integration circuit IN, and a voltage from the subtraction circuit SS It is characterized by adding a comparator CP for comparing a detection signal and generating a signal when the integrated voltage becomes smaller than the voltage detection signal.

Here, since the integral value of the voltage between the primary windings of the pulse transformer PT and time indicates the magnetic flux density of the core of the pulse transformer PT, the integrating circuit IN calculates the magnetic flux density of the core of the pulse transformer PT. It works as a magnetic flux density detector to detect. Then, the peak hold circuit PH detects the maximum magnetic flux density of the magnetic core of the pulse transformer PT, and supplies a voltage signal corresponding to the maximum magnetic flux density to the subtraction circuit SS. The set voltage source RP has a voltage corresponding to a predetermined appropriate set magnetic flux density Bd as shown in FIG. The subtraction circuit SS outputs a voltage signal corresponding to the magnetic flux density obtained by subtracting a predetermined appropriate set magnetic flux density Bd from the maximum magnetic flux density of the magnetic core of the pulse transformer PT, and outputs a voltage signal corresponding to the comparator CP.
Compares the magnetic flux density obtained by subtracting a predetermined appropriate set magnetic flux density Bd from the maximum magnetic flux density of the magnetic core of the pulse transformer PT with the actual magnetic flux density of the magnetic core of the pulse transformer PT. Therefore, the peak hold circuit PH, the set voltage source RP, and the subtraction circuit SS
The comparator CP works as a magnetic flux density setting level detector.

What is important here is that a predetermined appropriate set magnetic flux density Bd is determined as follows. Explaining also with reference to FIG. 2, the minimum value of the set magnetic flux density Bd is such that the magnetic flux density B1 of the high voltage pulse HP from the high voltage pulse generation circuit 5 is equal to the magnetic flux density B1 of the core of the pulse transformer PT due to the ripple voltage. It is preferable that the magnetic flux density is set so as not to exceed the maximum magnetic flux density Bp even if they are superimposed. In addition, since the current flows due to the inductance of the circuit, the non-conduction angle at which the bidirectional power control switch S1 is not turned on by design in each cycle of the commercial power supply voltage until the current stops flowing, that is, the dead angle. Although a time is provided, the maximum value of the set magnetic flux density Bd is preferably a magnetic flux density obtained by subtracting the magnetic flux density at a time substantially corresponding to the dead time from the maximum magnetic flux density. Therefore, the set magnetic flux density Bd is arbitrarily set in the range from the minimum value to the maximum value.

Next, the operation of this device will be described.
As described above, the ripple voltage is applied to the pulse transformer PT, and the power control switch of the high-voltage pulse generation circuit 5
When S2 is turned on by the control signal from the control unit 5B,
Capacitor C1-Pulse transformer PT-Inductor for resonance L2-
Resonant current in closed circuit of power control switch S2-capacitor C1
i1 flows. At the same time, due to the action of the pulse transformer PT, the resonance current i2 also flows through the closed circuit of the pulse transformer PT, the capacitance of the dust collection chamber 2, the capacitor C2, and the pulse transformer PT. In the positive half cycle of the resonance current i2, the voltage of the discharge electrode 2A of the dust collection chamber 2 increases in the negative direction, and in the negative half cycle of the resonance current i2, the negative voltage of the discharge electrode 2A of the dust collection chamber 2 increases. Decreases and returns to the starting voltage.

The magnetic flux density of the magnetic core of the pulse transformer PT is detected as a voltage by voltage detecting resistors R1 and R2 connected between the primary windings. The detected voltage is integrated by the integration circuit IN of the control unit 5B of the high-voltage pulse generation circuit 5, and a voltage-time product (VT) corresponding to the actual magnetic flux density is obtained. The peak hold circuit PH peak-holds the voltage-time product (VT) signal from the integration circuit IN, and generates a voltage peak value (for example, 1.9 Tesla) corresponding to the maximum magnetic flux density (for example, 1.9 Tesla) of the magnetic core of the pulse transformer PT.
t1) is detected and sent to the subtraction circuit SS. The subtraction circuit SS
From the voltage peak value corresponding to the maximum magnetic flux density of the core of the pulse transformer PT, the DC voltage corresponding to the set magnetic flux density Bd (for example, 0.6 Tesla) determined as described above from the set voltage source RP is subtracted. A voltage signal corresponding to the difference is sent to the comparator CP. The comparator CP compares the voltage signal with a voltage corresponding to the magnetic flux density of the core of the pulse transformer PT from the integration circuit IN, and sends an output signal to the control signal generator CC when the latter is lower than the former ( Time t2). The control signal generator CC receives the output signal and supplies a control signal to the power control switch S2 to turn it on.

Therefore, the high-voltage pulse generating circuit 5 generates the high-voltage pulse HP through the pulse transformer PT at substantially the same time t3 as the time t2, and the high-voltage pulse HP is connected to the capacitor C2.
Is applied between the discharge electrode 2A and the dust collection electrode 2B via By generating the high-voltage pulse HP at such a timing, as is clear from FIG. 2, the high-voltage pulse HP is generated when the ripple voltage drops to some extent, and the high voltage is applied to the ripple voltage in the pulse transformer PT. It can be seen that the magnetic flux density B2 corresponding to the voltage on which the pulse HP is superimposed does not exceed the maximum magnetic flux density.

Next, another embodiment of the present invention will be described with reference to FIG. As described above, the bidirectional power control switch S1 is not turned on by design in each cycle of the commercial power supply voltage until the current stops flowing because the current flows due to the inductance of the circuit and the like. This time is called dead time. If the power control switch S2 of the high voltage pulse generation circuit 5 is turned on at a set time before the end of the dead time, the high voltage pulse HP is turned on before the bidirectional power control switch S1 is turned on. Can be generated and terminated.

As can be seen from FIG. 3, the pulse transformer PT
Since the magnetic flux density of the magnetic core has a tendency to decrease until the conduction of the bidirectional power control switch S1, the set magnetic flux density Bd becomes maximum at the set time before the end of the dead time, but in this embodiment, the bidirectional power control The dead time during which the switch S1 is not turned on is determined from the design, and the pulse width of the high-voltage pulse HP and the conduction delay of the power control switch S2 of the high-voltage pulse generation circuit 5 can be known in advance from circuit constants. Considering this, the conduction time of the power control switch S2 can be fixed.

In this case, a voltage zero point in each cycle of the commercial power supply voltage is detected, and at an appropriate constant time within the dead time based on the voltage zero point, the control signal generator CC turns on the conduction control signal. Should be generated. For example, if the dead time is in the angle range from the voltage zero point to 20 degrees, it is preferable that the control signal generator CC generates the conduction control signal at an angle of about 15 degrees.

In the case of this embodiment, the integration circuit IN, the peak hold circuit PH, the subtraction circuit SS, the set voltage source RP, the comparator CP, or the functions corresponding to the functions of these circuits are omitted from the control unit 5B. Can be.

Although not shown, the integrating circuit IN of FIG. 1 includes a reset switch for resetting the integrated value to almost zero in each half cycle of the commercial power supply voltage. 2 and 3, the magnetic flux density of the pulse transformer, the ripple voltage component of the voltage applied to the dust collection chamber, and the polarity of the high-voltage pulse are displayed in reverse for convenience of explanation.

[0028]

The present invention has the features as described above, and can reduce the cross-sectional area of the magnetic core of the pulse transformer significantly by optimizing the generation timing of the high voltage pulse with respect to the ripple voltage. In addition, the size of the transformer can be reduced.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a pulse power supply for an electric dust collector according to the present invention.

FIG. 2 is a waveform diagram for explaining a pulse power supply device for an electric dust collector according to the present invention.

FIG. 3 is a waveform diagram for explaining a control method of the pulse power supply device for an electric dust collector according to the present invention.

[Explanation of symbols]

1 直流 DC high voltage power supply PT ──
Pulse transformer 2 ── Electric precipitator IN ──
Integrator 2A ── Discharge electrode PH ──
Peak hold circuit 2B 塵 Dust collection electrode RP ──
Set voltage source 3 高 DC high voltage power supply SS ──
Subtraction circuit 4 ── Current limiting impedance CP ──
Comparator 5 ── High-voltage pulse generator circuit CC ──
Control signal generator S1 双方 向 Bidirectional power control switch S2 電力 Power control switch

Claims (4)

[Claims] 1. A bidirectional power control switch for controlling AC power, a control unit for controlling the operation of the bidirectional power control switch, a step-up transformer, and a high voltage rectifier circuit. A first DC high-voltage power supply applied between discharge electrodes,
A second DC high-voltage power supply; and a high-voltage pulse generation circuit for pulsating the DC high voltage from the second DC high-voltage power supply, wherein the high-voltage pulse generation circuit generates a high-voltage pulse from the first DC high-voltage power supply. In a pulse power supply device for an electric precipitator applied between the dust collecting electrode and the discharge electrode so as to be superimposed on a DC high voltage from a high voltage power supply, the transformer is configured by exciting a ripple voltage between the dust collecting electrode and the discharge electrode. A magnetic flux density detector for detecting a magnetic flux density, a magnetic flux density setting level detector for generating a detection signal when the magnetic flux density of the transformer decreases from a maximum value by a predetermined value, and a detection from the magnetic flux density setting level detector And a control signal generator for receiving a signal and supplying a control signal to a power control switch of the high-voltage pulse generation circuit to make the power control switch conductive. 2. The magnetic flux density setting level detector according to claim 1, wherein the magnetic flux density detector is an integration circuit for detecting a product of a voltage applied to a winding of the transformer and a time of each cycle. A peak hold circuit for peak-holding the integrated value of the integration circuit, a set voltage source presenting a voltage corresponding to a set magnetic flux, a subtraction circuit for subtracting the voltage of the set voltage source from the voltage of the peak hold circuit, A pulse power supply for an electrostatic precipitator, comprising: a comparator for comparing a voltage signal from a subtraction circuit with an integration value of the integration circuit. 3. A bidirectional power control switch for controlling AC power with a dead time that does not turn on for a fixed period in each cycle, a control unit for controlling the operation of the bidirectional power control switch, a step-up transformer, and a high-voltage rectifier circuit. A first DC high-voltage power supply for applying a DC high voltage between the collection electrode and the discharge electrode,
DC high voltage power supply, and a high voltage pulse generating circuit for pulsing the DC high voltage from the second high voltage power supply,
The method of operating a pulse power supply for an electric precipitator, wherein the high voltage pulse generating circuit applies a high voltage pulse between the dust collecting electrode and the discharge electrode so as to superimpose a high voltage pulse on a DC high voltage from the first DC high voltage power supply. The period from the time point of the level reduced by a predetermined value from the maximum value of the magnetic flux density of the transformer due to the excitation of the ripple voltage between the dust collection electrode and the discharge electrode until immediately before the end of the dead time of the bidirectional power control switch, A method for operating a pulse power supply for an electric dust collector, wherein a high voltage pulse is applied between the dust collecting electrode and the discharge electrode. 4. A bidirectional power control switch for controlling AC power with a dead time that does not turn on for a fixed period in each cycle, a control unit for controlling the operation of the bidirectional power control switch, a step-up transformer, and a high-voltage rectifier circuit. A first DC high-voltage power supply for applying a DC high voltage between the collection electrode and the discharge electrode,
And a high-voltage pulse generating circuit for pulsing a high-voltage DC from the second high-voltage power supply, wherein the high-voltage pulse generating circuit generates a high-voltage pulse from the first high-voltage power supply.
A method of operating a pulse power supply for an electric precipitator applied between the dust collection electrode and the discharge electrode so as to be superimposed on a DC high voltage from a DC high voltage power supply, wherein the dead time of the bidirectional power control switch before the end is over. A method of operating a pulse power supply for an electric dust collector, wherein the high voltage pulse is applied between the dust collecting electrode and the discharge electrode at a set time.