JP2010104937A - Electrostatic dust collector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it is necessary to provide a complicated feedback circuit composed of a circuit for detecting a discharge current, a circuit for comparatively discriminating between the detected discharge current and a set current and a circuit for controlling an output voltage after the comparative discrimination of the detected discharge current and the set current conventionally in order to limit a discharge current flowing between a discharge electrode and an opposing electrode. <P>SOLUTION: The gate and the source of an FET 4 are short-circuited and inserted between a discharge electrode 1 and a high voltage power source 3. As a result, a current limiting circuit simple in configuration can be obtained that requires no complicated feedback circuit for detection of a discharge current, comparative discrimination of the detected current, and limitation of the discharge current by controlling an output voltage on the basis of the comparative discrimination result. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric dust collector that collects atmospheric dust, indoor dust, dust and the like in air conditioning and industrial fields.

  2. Description of the Related Art Conventionally, an electrostatic precipitator that collects particles is composed of two electrodes that are a pair of a discharge electrode and a counter electrode, and a positive or negative high voltage is applied to the discharge electrode to ground the counter electrode. When a high voltage is applied between the discharge electrode and the counter electrode, the gas insulation between the electrodes is broken and a current flows. This is called corona discharge. When suspended particles pass through the region where the corona discharge current flows, the particles collide with electrons moving in the corona discharge region, and the suspended particles are charged. Charged suspended particles receive the force of an electric field formed by a high voltage applied between the discharge electrode and the counter electrode, and are attracted and adhered to the counter electrode, whereby the suspended particles are removed.

  In a state where a high voltage is applied between the discharge electrode and the counter electrode, a corona discharge current flows between the discharge electrode and the counter electrode, but the impedance between the discharge electrode and the counter electrode (hereinafter referred to as load impedance). As the value decreases, the discharge current increases.

  The load impedance increases or decreases depending on the temperature and humidity of the air between the discharge electrode and the counter electrode. However, the load impedance does not vary greatly and the corona discharge is sustained when the temperature and humidity of the gas vary. However, when the discharge electrode and the counter electrode are wet with the cleaning water and do not dry, or when the collected substances are deposited on the discharge electrode and the counter electrode, the distance between the discharge electrode and the counter electrode is shortened, or floating particles are trapped. When the conductive substance that has been concentrated and contacts either the discharge electrode or the counter electrode, and the distance between the discharge electrode and the counter electrode is shortened, the load impedance is extremely reduced.

  When a high voltage is applied in a state where the load impedance is extremely lowered, the discharge current becomes extremely large, increasing the burden on the electric circuit system, and a large power source capacity is required. Therefore, in a situation where the load impedance is low, the electric circuit system is protected by limiting the flowing discharge current to a certain value or less, and the required power capacity is reduced.

  Conventionally, as a method of maintaining such a discharge current below a certain value, there is an electrostatic precipitator as shown in FIG.

  The electric dust collector shown in FIG. 4 includes a constant voltage circuit 102 that controls the voltage applied to the dust collection load 101 at a constant level, a high-voltage transformer 103 that generates the voltage applied to the load 101, a secondary side voltage doubler circuit 104, It comprises a secondary semiconductor element 105, a current detection resistor 106 for detecting the current to the dust collection load, and a constant current circuit 107 for controlling the current to the dust collection load to be constant.

  In a steady state, a high voltage is applied to the dust collection load 101 to constantly generate a corona discharge between the poles of the dust collection load, so that the voltage applied to the load 101 is kept constant by the control of the constant voltage circuit 102. ing. However, the discharge current increases when the load impedance decreases due to the wetness of the dust collection load 101, the shortening of the insulation distance between the dust collection load electrodes due to the accumulation of the collected substance, the short circuit between the electrodes due to the flying conductive substance, and the like.

  When the discharge current increases, the voltage across the current detection resistor 106 increases. As the voltage rises, an increase in discharge current is detected by the constant current circuit 107. The constant current circuit 107 that detects the increase in the discharge current controls the constant voltage circuit 102 and the primary side semiconductor element 105 to reduce the input voltage to the high voltage transformer 103. When the input voltage to the high voltage transformer 103 decreases, the output voltage of the high voltage transformer 103 also decreases, and the voltage applied to the load 101 via the secondary side voltage doubler circuit 104 decreases. The constant current circuit 107 reduces the voltage input to the high-voltage transformer 104 until the current value detected by the current detection resistor 106 becomes equal to or less than the constant current set value set by the constant current circuit 107.

When the load impedance of the dust collection load 101 returns to a high state and the current value detected from the current detection resistor 106 is equal to or less than the constant current set value set by the constant current 108, the control of the constant current circuit 107 is lost. The voltage applied to the dust collection load 101 becomes constant again under the control of the constant voltage circuit 102 (see, for example, Patent Document 1).
JP 05-304770 A

  In such a conventional method of limiting the discharge current, there are a circuit for detecting the discharge current, a circuit for comparing and detecting the detected discharge current and the set current, and a circuit for controlling the output voltage after comparing and determining the detected current and the set current. All are necessary, and there is a problem that a complicated feedback control circuit is required to control the discharge current below a certain value.

  Therefore, there is a demand for an electrostatic precipitator that can limit the discharge current without using a complicated feedback circuit.

  As a method of realizing current limitation without using a complicated feedback circuit, the discharge current value is less than the Idss value of the field effect transistor by short-circuiting the gate and source of the field effect transistor and inserting it in the line through which the discharge current flows. Can be suppressed.

  Considering the withstand voltage of the control circuit, the normal feedback circuit is arranged on the low voltage side because it is easier and more reliable to arrange the detection circuit on the low voltage side. When this occurs, there is a problem that a control circuit with a high withstand voltage is required.

  Therefore, there is a need for an electrostatic precipitator equipped with a current limiting means that can be arranged on both the high-pressure side and the low-pressure side without considering the withstand voltage against the control circuit even when arranged on the high-voltage side.

  When the discharge electrode and the counter electrode are short-circuited, there is a problem that a high voltage may be applied to both ends of the current limiting unit and the use withstand voltage may be exceeded only by arranging the current limiting unit.

  Therefore, an electric current limiting means is inserted in series with the current limiting means, and even when the discharge electrode and the counter electrode are short-circuited, the current limiting means bears the applied voltage, and the current limiting means does not impose a voltage burden. A dust collector is required.

  By using multiple low-voltage, low-priced, general-purpose resistors in series as current-limiting means, it is not necessary to use special high-voltage resistors even when the current-limiting means is placed on the high-voltage side. In addition, it can be easily applied to high power circuits. Moreover, it can be arranged on the low pressure side with no problem with the same configuration.

  The current limiting means is inserted between the smoothing element of the high-voltage output circuit and the dust collecting means, so that the current limiting means effectively acts against the transient discharge of the current charged in the smoothing element. be able to.

  Further, by inserting the current limiting means in the middle of the current limiting means or at the end of the current limiting means, the voltage applied to the current limiting means can be reduced, and it is advantageous to ensure the withstand voltage of the current limiting means.

  Further, since the Idss characteristic of the current limiting means is uniquely determined depending on the part, there is a problem that a single constant current limiting means may not ensure a desired constant current value in terms of dust collection performance.

  Therefore, there is a demand for an electrostatic precipitator capable of arranging a plurality of current limiting means in parallel and increasing the constant current value as necessary.

  In addition, in the unlikely event that the current limiting means is damaged in an open state for some reason, there is a problem that the discharge current does not flow through the dust collection load and the dust collection performance cannot be exhibited.

  Therefore, there is a demand for an electrostatic precipitator that can be determined to be abnormal when current detection means is added and when it is detected that the current is below a certain set value.

  In addition, an abnormality determination circuit can be realized with a simple configuration by assembling a circuit that drives the relay in accordance with the voltage across the detection resistor.

  Also, at the moment when the current limiting means is broken in the open state, the load on the high-voltage output circuit suddenly becomes lighter, so that the high-voltage output control cannot follow, and a very high voltage may be output even though it is instantaneous. There is a problem.

  Therefore, there is a demand for an electrostatic precipitator that can discharge a momentary overvoltage and protect the high voltage circuit by providing a space gap in the output stage of the high voltage output.

  In addition, when an abnormality occurs, the high voltage output is stopped and the state is output to the outside so that the status of the electrostatic precipitator can be informed to the outside.

  The present invention solves such a conventional problem, such as a conventional circuit for detecting a discharge current, a circuit for comparing and detecting a detected discharge current and a set current, and after comparing and determining a detected current and a set current. An object of the present invention is to provide an electrostatic precipitator that eliminates the need for a circuit that controls the output voltage and that can limit the discharge current using only electronic components.

  Another object of the present invention is to provide an electrostatic precipitator capable of suppressing the discharge current value to be equal to or less than the Idss value of the field effect transistor by short-circuiting the gate and source of the field effect transistor and inserting the same into a line through which the discharge current flows. It is said.

  It is another object of the present invention to provide an electrostatic precipitator equipped with current limiting means that can be arranged on both the high voltage side and the low voltage side without having to consider the withstand voltage against the control circuit even when arranged on the high voltage side. Yes.

  Also, when the discharge electrode and the counter electrode are short-circuited, the current limiting means alone is inserted in series with the current limiting means so that a high voltage is applied to both ends of the current limiting means and the withstand voltage is not exceeded. It is an object of the present invention to provide an electrostatic precipitator that bears an applied voltage by a current-limiting means even when the electrode and the counter electrode are short-circuited and does not place a voltage on the current-limiting means.

  In addition, it is necessary to use a special high withstand voltage resistor even when the current limiting means is arranged on the high voltage side by inserting a plurality of low-voltage inexpensive general-purpose resistors in series for the current limiting means. In addition, application to a high-power circuit is facilitated. Furthermore, it aims at providing the electrostatic precipitator which can be arrange | positioned without a problem also in the low voltage | pressure side by the same structure.

  In addition, the current limiting means is inserted between the smoothing element of the high-voltage output circuit and the dust collecting means, so that the current limiting means can be effectively used for transient discharge of the current charged in the smoothing element. It aims at providing the electric dust collector which can be made to act.

  In addition, by inserting the current limiting means in the middle of the current limiting means or at the end of the current limiting means, the voltage applied to the current limiting means can be reduced, and it is advantageous to ensure the withstand voltage of the current limiting means. The object is to provide a device.

  Moreover, since the Idss characteristic of the current limiting means is uniquely determined depending on the component, an object is to provide an electric dust collector that can increase the constant current value by arranging a plurality of current limiting means in parallel as necessary. It is said.

  Also, if the current limiting means is broken in any open state due to some reason, current will not flow to the dust collection load and dust collection performance will not be achieved. An object of the present invention is to provide an electrostatic precipitator that can be determined to be abnormal when detected.

  It is another object of the present invention to provide an electrostatic precipitator capable of realizing an abnormality determination circuit with a simple configuration by assembling a circuit that drives a relay according to the voltage across the detection resistor.

  Also, at the moment when the current limiter breaks in the open state, the load on the high-voltage output circuit suddenly becomes lighter, so the high-voltage output control cannot follow and there is a possibility that a very high voltage will be output even momentarily. Therefore, an object of the present invention is to provide an electrostatic precipitator that can cope with an instantaneous overvoltage by providing a space gap in the output stage of the high-voltage output and protect the high-voltage circuit from the overvoltage.

  Another object of the present invention is to provide an electrostatic precipitator capable of informing the outside of the state of the electrostatic precipitator by stopping the high-voltage output in the event of an abnormality and outputting the state to the outside.

  In order to achieve the above object, the electrostatic precipitator of the present invention has a dust collecting means comprising a discharge electrode and a counter electrode, a high voltage applying means for applying a high voltage to the discharge electrode, and the discharge electrode facing the discharge electrode. Current limiting means for limiting the discharge current flowing between the electrodes is provided, and the discharge current can be limited without using a feedback circuit.

  According to the present invention, the conventional circuit for detecting the discharge current, the circuit for comparing and detecting the detected discharge current and the set current, and the circuit for controlling the output voltage after comparing and determining the detected current and the set current are unnecessary. Thus, an electrostatic precipitator capable of limiting the discharge current only with electronic components can be obtained.

  Further, the current limiting means is characterized in that the gate and source of the field effect transistor are short-circuited and inserted into a line through which a discharge current flows.

  According to the present invention, there is provided an electric dust collector capable of suppressing a discharge current value to be equal to or less than an Idss value of a field effect transistor by short-circuiting the gate and source of the field effect transistor and inserting the same into a line through which a discharge current flows. can get.

  Further, the current limiting means is arranged on the high voltage side or the low voltage side of the high voltage applying means.

  According to the present invention, there is no need to consider the withstand voltage for the control circuit even when arranged on the high voltage side, and an electric dust collector equipped with current limiting means that can be arranged on both the high voltage side and the low voltage side is obtained. It is done.

  Further, it is characterized in that current limiting means for limiting a transient discharge current flowing between the dust collecting means and the high voltage applying means is provided.

  According to the present invention, even when the discharge electrode and the counter electrode are short-circuited, the current limiting means is inserted in series with the current limiting means, and even when the discharge electrode and the counter electrode are short-circuited, the current limiting means bears the applied voltage. By doing so, it is possible to obtain an electrostatic precipitator that does not place a voltage burden on the current limiting means.

  In addition, a plurality of low withstand voltage resistors are arranged in series and inserted into the current limiting means.

  And according to the present invention, a plurality of low-voltage low-priced general-purpose resistors are used in series and inserted into the current-limiting means, so that even when the current-limiting means is arranged on the high-voltage side, It is not necessary to use a withstand voltage resistor, and application to a high power circuit is facilitated. In addition, an electrostatic precipitator that can be disposed on the low-pressure side without any problem with the same configuration can be obtained.

  Further, the current limiting means is arranged between the high voltage circuit smoothing element of the high voltage applying means and the dust collecting means.

  According to the present invention, the current limiting means is inserted between the smoothing element of the high-voltage output circuit and the dust collecting means, so that the current limiting means can be used against transient discharge of the current charged in the smoothing element. An electrostatic precipitator that can effectively act is obtained.

  Further, the current limiting means is arranged on the high voltage side of the high voltage applying means, and the current limiting means is arranged in the middle of the current limiting means or at the output end.

  According to the present invention, it is possible to reduce the voltage applied to the current limiting means by inserting the current limiting means in the middle or at the end of the current limiting means, and it is advantageous to ensure the withstand voltage of the current limiting means. An electrostatic precipitator that can be obtained is obtained.

  Further, a plurality of current limiting means are arranged and inserted in parallel.

  According to the present invention, since the Idss characteristic of the current limiting means is uniquely determined according to the part, an electric dust collector that can increase the constant current value by arranging a plurality of current limiting means in parallel as necessary. Is obtained.

  Further, the current detection unit is inserted in series with the current limiting unit, and when the current of the current detection unit is equal to or less than a set value, it is determined that the current limiting unit is abnormal.

  And according to the present invention, if the current limiting means breaks in an open state for some reason, the current detection means is added and no current flows because the current does not flow to the dust collecting load and the dust collecting performance cannot be exhibited. If this is detected, an electrostatic precipitator that can be determined to be abnormal is obtained.

  Further, as the abnormality determining means, a voltage-driven relay circuit is used.

  And according to this invention, the electric dust collector which can implement | achieve an abnormality judgment circuit with a simple structure by assembling the circuit which drives a relay according to the both-ends voltage of a detection resistor is obtained.

  Further, an overvoltage protection gap is inserted in the output stage of the high voltage applying means.

  According to the present invention, at the moment when the current limiting means is broken in the open state, the load of the high-voltage output circuit is suddenly lightened, so that the high-voltage output control cannot be followed and a very high voltage is output although it is instantaneous. Although there is a possibility, an electrostatic precipitator capable of protecting the high voltage circuit from an instantaneous overvoltage can be obtained by providing a space gap in the output stage of the high voltage output.

  Further, the present invention is characterized by comprising an external output means for stopping the output of the high voltage applying means by the output of the abnormality determining means and outputting the abnormal state of the current limiting means and the state of the high voltage applying means to the outside.

  According to the present invention, an electrostatic precipitator that can inform the outside of the state of the electrostatic precipitator is obtained by stopping the high-voltage output in the event of an abnormality and outputting the state to the outside.

  According to the present invention, the discharge current flowing between the discharge electrode and the counter electrode is limited to the Idss value or less by short-circuiting the gate and the source of the semiconductor and inserting it into the current line. This eliminates the need for an output voltage feedback circuit comprising a conventional circuit for detecting a discharge current, a circuit for comparing and detecting the detected discharge current and a set current, and a circuit for controlling the output voltage after comparing and determining the detected current and the set current. Thus, an electrostatic precipitator that can limit the discharge current with a simple configuration can be provided.

  In order to achieve the above object, the invention according to claim 1 of the present invention is a dust collecting means composed of a discharge electrode and a counter electrode, a high voltage applying means for applying a high voltage to the discharge electrode, and the discharge electrode. Current limiting means for limiting the discharge current flowing between the counter electrode and the counter electrode, characterized in that the discharge current can be limited without using a feedback circuit, a circuit for detecting a discharge current as in the prior art, A circuit for determining and comparing the detected discharge current and the set current and a feedback circuit for controlling the output voltage after comparing and determining the detected current and the set current are unnecessary, and the discharge current can be limited only by electronic components. .

  According to a second aspect of the present invention, in order to achieve the above object, the current limiting means is short-circuited between the gate and the source of the field effect transistor and inserted into a line through which a discharge current flows. By having the gate and source of the field effect transistor short-circuited and inserted into the line through which the discharge current flows, the discharge current value can be suppressed below the Idss value of the field effect transistor.

  According to the third and fourth aspects of the present invention, in order to achieve the above object, the current limiting means is arranged on the high voltage side or the low voltage side of the high voltage applying means. Even in the case of being arranged in the circuit, there is no need to consider the withstand voltage with respect to the control circuit, and there is an effect that it can be arranged on both the high voltage side and the low voltage side.

  In order to achieve the above object, the invention according to claim 5 of the present invention comprises current limiting means for limiting a transient discharge current flowing between the dust collecting means and the high voltage applying means. The current-limiting means is inserted between the smoothing element of the high-voltage output circuit and the dust collecting means, so that the current-limiting means can be used for transient discharge of the current charged in the smoothing element. It has the effect | action that a means can be made to act effectively.

  In order to achieve the above object, the present invention according to claims 6 to 8 is characterized in that a plurality of low withstand voltage resistors are arranged in series in the current limiting means. By using multiple low-voltage low-priced general-purpose resistors in series as current-limiting means and inserting them, there is no need to use special high-voltage resistance even when the current-limiting means is placed on the high voltage side. In addition, it can be easily applied to a high power circuit. Furthermore, it has the effect | action that it can arrange | position without a problem also on the low voltage | pressure side with the same structure.

  The invention described in claim 9 of the present invention is characterized in that, in order to achieve the above object, the current limiting means is disposed between the high voltage circuit smoothing element of the high voltage applying means and the dust collecting means. By inserting the current limiting means between the smoothing element of the high-voltage output circuit and the dust collecting means, the current limiting means effectively acts against the transient discharge of the current charged in the smoothing element. It has the effect that it can be made.

  According to the tenth aspect of the present invention, in order to achieve the above object, the current limiting means is disposed on the high voltage side of the high voltage applying means, and the current limiting means is provided in the middle of the current limiting means or at the output end. The current limiting means is inserted in the middle or at the end of the current limiting means to reduce the voltage applied to the current limiting means and to ensure the withstand voltage of the current limiting means. It has the effect that it can be advantageous.

  In order to achieve the above object, the invention according to claim 11 is characterized in that a plurality of current limiting means are arranged in parallel and the characteristic Idss of the current limiting means is the component. Since it is uniquely determined according to the requirement, it has an effect that the constant current value can be increased by arranging a plurality of current limiting means in parallel if necessary.

  According to the twelfth and thirteenth aspects of the present invention, in order to achieve the above object, the current detecting means is inserted in series with the current limiting means, and when the current of the current detecting means is equal to or less than a set value, If the current limiting means breaks in an open state due to some reason, current will not flow to the dust collecting load and the dust collecting performance cannot be demonstrated. Therefore, it is possible to determine that the dust collector is abnormal when it is detected that no current is flowing.

  In order to achieve the above object, the invention described in claim 14 is characterized in that a voltage-driven relay circuit is used as the abnormality determination means, and the voltage is detected according to the voltage across the detection resistor. By assembling a circuit for driving the relay, an abnormality determination circuit can be realized with a simple configuration.

  In order to achieve the above object, the present invention according to claim 15 is characterized in that an overvoltage protection gap is inserted in the output stage of the high voltage applying means, and the current limiting means is broken in an open state. At that moment, the load on the high-voltage output circuit suddenly becomes lighter, so the high-voltage output control cannot follow up and a very high voltage may be output although it is instantaneous, but there is a space gap in the output stage of the high-voltage output. By providing, it has the effect | action that a high voltage circuit can be protected from instantaneous overvoltage.

  According to the sixteenth and seventeenth aspects of the present invention, in order to achieve the above object, the output of the high voltage applying means is stopped by the output of the abnormality determining means, the abnormal state of the current limiting means and the state of the high voltage applying means It is characterized by having an external output means to output to the outside, and in the event of an abnormality, the high voltage output is stopped and the state is output to the outside so that the status of the electrostatic precipitator is informed to the outside Has the effect of being able to

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows the configuration of an electrostatic precipitator according to Embodiment 1 of the present invention. As shown in FIG. 1, the discharge electrode 1 and the counter electrode 2, the high voltage power source 3 as a high voltage applying means for applying a high voltage to the discharge electrode 1, and the discharge current flowing between the discharge electrode 1 and the counter electrode 2 are limited. It is comprised by FET4 as a current limiting means for doing.

  The discharge electrode 1 is connected to the high voltage application side of the high voltage power source 3, and the FET 4 whose gate and source are short-circuited is discharged from the high voltage power source 3 while the counter electrode 2 is connected to the other polarity of the high voltage power source 3 and the ground side. Insert between electrodes 1. When the load impedance between the discharge electrode 1 and the counter electrode 2 decreases, the voltage is constant and the discharge current increases. However, due to the Idss characteristics of the inserted FET 4, the discharge current does not flow beyond a specified current value. Even if the load impedance is reduced by the action of the FET 4, the discharge current can be kept below a certain value.

  In the present invention, an FET is used, but any semiconductor element having the same characteristics may be used. A constant current diode can also be used because it has the same effect.

  The FET 4 can also be used by being arranged on the low voltage side in the high voltage power source 3. However, as shown below, it is extremely effective to dispose near the discharge electrode 1 or the counter electrode 2 outside the high-voltage power supply 3.

  Regarding the arrangement of the FET 4, when the FET 4 is gate-driven, it is necessary to suppress the potential difference between the gate voltage and the source voltage within the rated value. However, in the present invention, the gate and source of the FET 4 are short-circuited. And the low voltage control circuit of the high voltage power source 3 can be separated. Therefore, the FET 4 can be arranged on the high voltage side without considering the gate breakdown voltage of the FET 4. In addition, when the FET 4 is arranged on the high voltage side, the FET 4 itself becomes a high voltage with respect to the ground potential, so that it is necessary to consider the insulation of the component itself with respect to the ground potential and the low potential similar to other high voltage components. Compared with securing a breakdown voltage in the control circuit, it is much easier.

  Further, since the FET 4 has a simple structure and is small in size, the FET 4 can be used in the vicinity of the discharge electrode 1 or the counter electrode 2 without being arranged in the high-voltage power source 3. Therefore, the FET 4 can be arranged not in the high-voltage power supply 3 but in the vicinity of the discharge electrode 1 or the counter electrode 2 and outside the high-voltage power supply 3.

  When a spark discharge occurs, the charge accumulated in the capacitance formed by the discharge electrode 1 and the counter electrode 2 is short-circuited, neutralized and emptied. As soon as the electrostatic capacity between the discharge electrode 1 and the counter electrode 2 becomes empty, the battery is charged. As a supply source of the charging current, charges accumulated in the high-voltage power supply 3 and charges accumulated outside the high-voltage power supply 3 are used. There is. The charge supply source in the high voltage power source 3 includes a smoothing capacitor in the circuit, and the charge accumulated outside the high voltage power source 3 exists between the high voltage cable connecting the high voltage power source 3 and the discharge electrode 1 and the ground. Stray capacitance.

  When the FET 4 is arranged in the high-voltage power supply 3, the current charged from the high-voltage power supply 3 can be suppressed when a spark discharge occurs, but the discharge of the charge accumulated in the stray capacitance existing outside the high-voltage power supply 3 is It cannot be suppressed.

  On the other hand, when the FET 4 is disposed in the vicinity of the discharge electrode 1 or the counter electrode 2, the charge accumulated in the stray capacitance existing outside the high-voltage power supply 3 when spark discharge occurs also passes between the discharge electrode 1 and the counter electrode 2 through the FET 4. Therefore, the transient current accumulated outside the high-voltage power supply 3 can also be suppressed. Therefore, by disposing the FET 4 outside the high-voltage power supply 3, the energy of the spark discharge itself when the spark discharge is generated can be reduced compared to the case where the FET 4 is disposed in the high-voltage power supply 3, and the dust collection efficiency surface, This is advantageous in terms of electrical noise. When electrical noise due to spark discharge is reduced, not only the electrical stress on the high-voltage power supply 3 is reduced, but also noise countermeasures applied to the detection circuit and the control circuit can be reduced. It can contribute to reduction and improvement of reliability.

  However, when the FET 4 is disposed in the vicinity of the discharge electrode 1, it is necessary to consider insulation from the counter electrode 2 and the ground potential.

  In addition, when the FET 4 is installed in the vicinity of the counter electrode 2, in order to return the current to the high-voltage power supply 3 by reliably passing the spark discharge current through the FET 4 while avoiding the bypass of the current due to other grounded route or capacitor coupling, Consideration for insulation is necessary in the route through which current flows.

(Embodiment 2)
FIG. 2 shows the configuration of an electrostatic precipitator according to Embodiment 2 of the present invention. As shown in FIG. 2, the discharge electrode 1 and the counter electrode 2, the high voltage power source 3 as a high voltage applying means for applying a high voltage to the discharge electrode 1, and the discharge current flowing between the discharge electrode 1 and the counter electrode 2 are limited. FET 4 as current limiting means and low-voltage resistance set 5 as current limiting means.

  When the FET 4 is arranged on the high voltage side in the high-voltage power supply 3, if only the FET 4 is arranged, when the discharge electrode 1 and the counter electrode 2 are short-circuited, the entire high voltage is applied to both ends of the FET 4. In this case, the FET 4 is required to have a very high breakdown voltage, but at present there is no semiconductor having a single component with a breakdown voltage of several kV required for the electrostatic precipitator. Therefore, as a method of increasing the breakdown voltage, there is a method of increasing the breakdown voltage by connecting semiconductors in series. However, as the applied voltage becomes higher, more semiconductors must be used, which is disadvantageous in terms of cost and size.

  Therefore, a low breakdown voltage resistance set 5 is inserted in series with the FET 4 as current limiting means. By inserting a resistor in series with the FET 4, the resistor bears the applied voltage even when the discharge electrode 1 and the counter electrode 2 are short-circuited, so that the FET 4 does not need to consider the voltage across the short-circuit.

  Regarding the selection of the resistor to be used, there is a withstand voltage sufficient to bear the entire voltage when the discharge electrode 1 and the counter electrode 2 are short-circuited, and an electric power that can be used by supplying a discharge current necessary for charging floating particles in a steady state. Although required, such a resistor has a very high voltage, so it has a special structure and large size, is very expensive, and is not readily available.

  Therefore, consider using a plurality of resistors in series. Even if the discharge electrode 1 and the counter electrode 2 are short-circuited and all voltages are applied to both ends of the low-breakdown-voltage resistance set 5, each resistor bears a voltage, so the voltage to be borne per one can be low, Similarly, in terms of power, each resistor bears the W number, so that the resistance per one can be reduced with a small number of W. Therefore, this configuration makes it possible to use a general-purpose low withstand voltage resistor, which is very advantageous in terms of cost and availability.

  Further, by disposing the FET 4 between the resistances of the low breakdown voltage resistance set 5 or at the end, the voltage corresponding to the resistance drops due to the discharge current flowing through the low breakdown voltage resistance set 5 in the steady state. Therefore, the potential of the FET 4 itself viewed from the ground potential can be lowered, which is advantageous in consideration of insulation.

  The low-breakdown-voltage resistance set 5 is effective not only for short-circuiting between the discharge electrode 1 and the counter electrode 2 but also for mitigating a large current generated during spark discharge, and can reduce electrical stress on the high-voltage power supply 3. . When the low-breakdown-voltage resistor set 5 is arranged in the high-voltage power supply 3, it is necessary to arrange it on the output side, which is a stage subsequent to the smoothing element of the high-voltage output circuit. When a spark discharge occurs, the charge charged in the smoothing element is also released as a transient current to the electrostatic capacitance component formed from the discharge electrode 1 and the counter electrode 2, but the low breakdown voltage resistance set 5 is more than the smoothing element of the high-voltage circuit. However, in the case where it is arranged in the preceding stage, since there is no FET 4 in the route through which the charge discharged from the smoothing element moves, this transient current cannot be limited. Therefore, the low-breakdown-voltage resistance assembly 5 is disposed after the smoothing element in the high-voltage power supply 3. As a result, the FET 4 can suppress the electric charge released from the smoothing element at the time of spark discharge toward the electrostatic capacitance formed by the discharge electrode 1 and the counter electrode 2, and at the same time the electrical stress on the high-voltage circuit is reduced. In addition, the energy of the spark discharge itself can be reduced.

  Since the spark discharge current is a large current composed of a high frequency component, an element having an inductance component is also effective as a factor for limiting the large current. However, when the discharge electrode 1 and the counter electrode 2 are short-circuited, the inductance does not act as a resistance element because the output of the high-voltage power supply 3 is a direct current. At this time, the entire high voltage is applied to both ends of the FET 4. In order to avoid this, it is necessary to use a resistor as the current limiting means.

  Further, since the Idss characteristic of the FET 4 is uniquely determined by the part, there is a case where a discharge current value necessary for dust collection performance cannot be ensured if only one part is used. In such a case, a desired discharge current value can be secured by connecting a plurality in parallel and flowing a current in parallel. Further, by using a plurality of devices in parallel, it is possible to prevent the electric circuit from being completely opened even if one component is damaged, and it is possible to continue the discharge current.

(Embodiment 3)
FIG. 3 shows the configuration of an electrostatic precipitator according to Embodiment 3 of the present invention. As shown in FIG. 3, the discharge electrode 1 and the counter electrode 2, the high voltage power source 3 as a high voltage applying means for applying a high voltage to the discharge electrode 1, and the discharge current flowing between the discharge electrode 1 and the counter electrode 2 are limited. FET 4 as current limiting means, low withstand voltage resistor set 5 as current limiting means, current detection resistor 6 as current detecting means, relay circuit 7 as abnormality determining means, external output circuit as external output means 8 and a discharge gap 9.

  If the FET 4 is damaged in an open state for some reason, a high voltage is not applied between the discharge electrode 1 and the counter electrode 2, and a discharge current does not flow between the electrodes. If the current does not flow, the suspended particles cannot be charged and the suspended particles cannot be collected, so the dust collection performance becomes zero. In order to detect this state, a current detection resistor 6 is installed, and the state of the current flowing between the discharge electrode 1 and the counter electrode 2 is detected by the voltage across the resistor.

  Further, at the moment when the FET 4 is opened, the output voltage control cannot follow the sudden change in the output load, and the output voltage may rise suddenly even for a moment. When the output voltage rises rapidly, not only does it cause stress on the high voltage circuit, but in the worst case, the high voltage circuit itself may be damaged due to excessive breakdown voltage of the high voltage circuit.

  In order to prevent damage to the high voltage circuit due to overvoltage, a discharge gap 9 is inserted between the discharge electrode 1 and the counter electrode 2. The discharge operating voltage of the discharge gap 9 is set within the breakdown voltage of the high voltage circuit. As a result, even if the output voltage rises momentarily due to the FET 4 opening, the output voltage rise is suppressed by the discharging action of the discharge gap 9, and the high-voltage circuit is protected from overvoltage without applying a voltage higher than the withstand voltage. be able to.

  A method for determining the abnormal state of the FET 4 open is realized by a relay circuit that is driven by the voltage across the detection resistor. The threshold value of the relay drive voltage is set by taking a margin into the minimum value of the relay drive voltage (return voltage) ≦ the minimum value of the discharge current that can secure the dust collection performance in the steady state × the resistance value of the current detection resistor 6. With this setting, in the state where the discharge current that can be collected in the steady state is flowing, the voltage across the current detection resistor 6 is larger than the relay drive voltage minimum value (return voltage) of the relay circuit 7, so the relay coil Excited state. When the FET 4 is opened and the discharge current decreases and the discharge current falls below the set value, the voltage across the current detection resistor 6 falls below the minimum relay drive voltage (return voltage) of the relay circuit 7 and the excitation of the relay coil is released. It becomes the state. When the excitation state of the relay is reversed due to the change in state of the FET 4, the contact output state of the relay is also reversed. An abnormal state of the FET 4 is determined using the inversion of the output state.

  When this determination is made, it is necessary to confirm that the operation command or operation state of the high-voltage power supply 3 is ON. Here, a relay is used, but a relay that can be driven by a voltage or a photocoupler can also be used without any problem.

  As a method of stopping the output of the high-voltage power supply 3 at the time when a decrease in the discharge current is detected, the output state of the relay circuit 7 is incorporated in the operation stop circuit of the high-voltage power supply 3 as an interlock. Thereby, when the output of the relay circuit is reversed during the steady operation of the high-voltage power supply 3, the abnormality of the FET 4 can be detected and the high-voltage output can be stopped.

  In order to accurately output the abnormal state of the FET 4 to the outside by the external output circuit 8, the output of the relay circuit 7 and the operation state output of the high voltage power source 3 are taken in, the high voltage power source 3 is in the operation state and the relay output state is inverted. At this point, it is determined that the FET 4 is abnormal. By outputting an abnormal signal to the outside after abnormality determination, the abnormal state of the FET 4 can be notified to the outside.

  The present invention can be applied to all electrostatic precipitators that collect suspended particles.

1 is a configuration diagram of an electric dust collector according to an embodiment of the present invention. 1 is a configuration diagram of an electric dust collector according to an embodiment of the present invention. 1 is a configuration diagram of an electric dust collector according to an embodiment of the present invention. Configuration diagram of electrostatic precipitator that maintains constant discharge current of other conventional examples

Explanation of symbols

1 Discharge electrode 2 Counter electrode 3 High voltage power supply 4 FET
5 Resistance set with low breakdown voltage 6 Current detection resistor 7 Relay circuit 8 External output circuit 9 Discharge gap

Claims (17)

Dust collecting means composed of a discharge electrode and a counter electrode, a high voltage applying means for applying a high voltage to the discharge electrode, and a current limiting means for limiting a discharge current flowing between the discharge electrode and the counter electrode An electrostatic precipitator capable of limiting the discharge current without using a feedback circuit. 2. The electrostatic precipitator according to claim 1, wherein the current limiting means is short-circuited between the gate and source of the field effect transistor and inserted into a line through which a discharge current flows. 3. The electrostatic precipitator according to claim 1, wherein the current limiting means is disposed on the high voltage side of the high voltage applying means. 3. The electrostatic precipitator according to claim 1, wherein the current limiting means is arranged on the low-voltage ground side of the high voltage applying means. The electric dust collector according to any one of claims 1 to 4, further comprising current limiting means for limiting a transient discharge current flowing between the dust collecting means and the high voltage applying means. 6. The electrostatic precipitator according to any one of claims 1 to 5, wherein a plurality of low withstand voltage resistors are inserted in series in the current limiting means. The electric dust collector according to any one of claims 1 to 6, wherein the current limiting means is arranged on the high voltage side of the high voltage applying means. The electric dust collector according to any one of claims 1 to 6, wherein the current limiting means is disposed on the low voltage ground side of the high voltage applying means. 9. The electrostatic precipitator according to claim 1, wherein the current limiting means is disposed between the high voltage circuit smoothing element of the high voltage applying means and the dust collecting means. 10. When the current limiting means is arranged on the high voltage side of the high voltage applying means, the current limiting means is arranged in the middle of the current limiting means or at the output end. The electric dust collector in any one of. The electric dust collector according to claim 1, wherein a plurality of current limiting means are arranged and inserted in parallel. The electric dust collector according to any one of claims 1 to 11, wherein a current detecting means is inserted in series with the current limiting means. 13. The electrostatic precipitator according to claim 1, further comprising an abnormality determination unit that determines that the current limiting unit is abnormal when the current of the current detection unit is equal to or less than a set value. 14. The electrostatic precipitator according to claim 1, wherein a voltage-driven relay circuit is used as the abnormality determining means. The electrostatic precipitator according to claim 1, wherein an overvoltage protection gap is inserted in an output stage of the high voltage applying means. The electrostatic precipitator according to claim 1, wherein the output of the high voltage applying unit is stopped by the output of the abnormality determining unit. 17. The electrostatic precipitator according to claim 1, further comprising an external output unit that outputs an abnormal state of the current limiting unit and a state of the high voltage applying unit to the outside.

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