WO2009091273A1 - Corona discharge treater with resonant voltage multiplication - Google Patents

Corona discharge treater with resonant voltage multiplication Download PDF

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Publication number
WO2009091273A1
WO2009091273A1 PCT/RS2008/000004 RS2008000004W WO2009091273A1 WO 2009091273 A1 WO2009091273 A1 WO 2009091273A1 RS 2008000004 W RS2008000004 W RS 2008000004W WO 2009091273 A1 WO2009091273 A1 WO 2009091273A1
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Prior art keywords
voltage
resonant
inverter
power
circuit
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PCT/RS2008/000004
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French (fr)
Inventor
Nandor Burany
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Nandor Burany
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Priority to PCT/RS2008/000004 priority Critical patent/WO2009091273A1/en
Publication of WO2009091273A1 publication Critical patent/WO2009091273A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T19/00—Devices providing for corona discharge
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode

Definitions

  • the field of invention is apparatus for treating the surface of polymer and other film materials with a high voltage gaseous discharge called corona.
  • the treatment of conductive and non-conductive materials is a well established process to enhance their adhesion to printing inks and glues.
  • the sheet or web of the material is conveyed over a metal roller which forms one electrode of the treater.
  • the other electrode is on a small distance from the metal roller and runs parallel with its axis.
  • the transformer's primary is supplied from an appropriately regulated electronic generator (101). Corona is formed between the electrodes (104 and 105) in the treating station (103).
  • the required voltage between the electrodes (104 and 105) is about 10 kV rms., its frequency can be from some kHz to some 10 kHz. By modern treaters frequencies in the 20 kHz to 50 kHz frequency range are preferable.
  • the present invention replaces the high voltage transformer used by corona treaters with a resonant circuit comprising a high voltage inductor and a high voltage capacitor.
  • An electronic generator supplies the resonant circuit at its resonant frequency or near to the resonant frequency.
  • the high voltage required for treatment is generated by voltage multiplication in the resonant circuit.
  • the high voltage inductor is divided into segments to easily withstand high voltage.
  • the capacitor is constructed by series connection of medium voltage units. This way the design and manufacturing of the a.c. voltage multiplication is simplified, compared to the traditional implementation with transformer.
  • the electronic generator is a mains rectifier followed by a resonant inverter.
  • the inverter is synchronized to the resonant frequency of the inductor-capacitor network by a phase locked loop circuit.
  • a power feedback circuit calculates the output power of the electronic generator and corrects the operating frequency of the inverter to adjust the power for treatment to the required level.
  • a voltage feedback circuit measures the output voltage of the voltage multiplier and corrects the operating frequency of the inverter to avoid overload conditions.
  • the treater constructed by use of electronic generator followed by resonant circuit is suitable for the treatment of any standard materials. Similar efficiency and similar volume of the proposed generator with resonant circuit can be achieved as by the combination of electronic generator with high voltage transformer. Design and manufacturing of the high voltage transformer is replaced by a simpler design and manufacturing of a high voltage inductor. The required capacitor can be combined from standard low voltage or medium voltage units. Oil bath for transformer insulation and cooling is eliminated by resonant circuit voltage multiplication.
  • Fig. 1 is a block diagram explaining the prior art.
  • the electronic generator supplies the treating station through a transformer with high- voltage secondary winding.
  • Fig. 2 is the block diagram of the solution of the treater system proposed by this invention.
  • the electronic generator supplies the treating station through an LC resonant circuit.
  • Fig. 3 is the block diagram of the electronic generator from Fig. 2, suitable for driving the resonant circuit.
  • Fig. 4 shows a more detailed block diagram of the electronic generator from Fig. 2 and Fig. 3, together with the resonant circuit and the treating station model.
  • Fig. 5 shows typical waveforms of voltages and currents of the electronic generator and the resonant circuit.
  • Fig. 6 shows one possible implementation of the high voltage inductor by series connection of low voltage or medium voltage inductors with ferrite cores.
  • Fig. 7 shows a second possible implementation of the high voltage inductor as a segmented air cored winding.
  • the proposed solution for carrying out corona treatment is shown in Fig. 2.
  • the electronic generator (101) supplies the electrodes (104 and 105) of the treating station (103) through a resonant circuit (201).
  • the generator is supplied from one phase or three phase, low voltage distribution network.
  • the required voltage multiplication is achieved by the resonant circuit (201) comprising a high voltage inductor (202) and a high voltage capacitor (203).
  • the voltage multiplication obtained by resonant circuit is on similar level as the multiplication by transformer (102) in the prior art shown in Fig. 1.
  • FIG. 3 Block diagram of the electronic generator (101) suitable to drive the resonant circuit (201) is shown in Fig. 3.
  • the rectifier (301) can be a simple, unregulated diode circuit. For higher power levels an active power factor correction (PFC) rectifier is preferable.
  • the transformer (303) with 1:1 turn's ratio is connected to the output of the inverter. This position of the transformer (303) is preferable as a small size ferrite core device can be used thanks to the high operating frequency of the inverter.
  • FIG. 4 A more detailed circuit diagram of the best mode of carrying out the electronic generator (101) completed with the resonant voltage multiplier circuit (201) and the model (404) of the treating station (103) is shown in Fig. 4.
  • the loading effect of the treating station (103) in the actual operating point is represented with parallel connection of the parasitic capacitance (412) of the electrodes (104 and 105) and the equivalent load resistance (413).
  • the equivalent load resistance (413) is calculated from the required corona power and corona voltage as:
  • the inverter (302) operates in square wave mode, generating pulses (501) of alternating polarity with amplitude equal to the rectified voltage V 1n , as shown in Fig. 5.
  • the operating frequency of the inverter (302) is equal to the frequency of resonance of the resonant circuit (201) or it is near to it. Thanks to the filtering effect of the resonant circuit (201), the inductor (202) current (502) is approximately sinusoidal.
  • the voltage multiplication factor of the resonant circuit (201) with the equivalent load (404) of the treating station (103), but without considering the losses in the resonant inductor (202) and resonant capacitor (203) is:
  • the parasitic capacitance (412) of the treating station is incorporated in the resonant capacitor (203) to simplify the calculations
  • the voltage multiplication factor has its maximal value at the frequency: f - f fix which is near to the resonant frequency f o by high values of the loaded quality factor Q L .
  • the maximal value is calculated by use of formula:
  • the power components of the rectifier-inverter cascade (301 and 302) driving the resonant circuit (201) are explained in the further text by use of Fig. 4..
  • An electromagnetic interference (EMI) filter (401) is necessary at the input to moderate the disturbances feed back to the mains.
  • the single phase rectifier bridge (402) is combined with a boost stage (403) with power factor correction (PFC) capability. This way not only near unity power factor is achieved, but the rectified voltage V n , is regulated to a constant average value, so the operation of the inverter is with less perturbations.
  • a three phase rectifier, also with PFC is preferable.
  • the resonant inverter (302) is of bridge type, comprising four power MOSFETs or IGBT switches (404). The switches are turned on and off in diagonal pairs for one half of the switching period. This way a square wave voltage, driving the isolation transformer (303) is generated.
  • the transformer (303) transmits the square voltage to the input of the resonant multiplier (201) without significant change of amplitude or distortion of waveform.
  • a transformer (303) with some voltage boost would be convenient to minimize resonant circuit (201) size but this usually leads to parasitic resonances in the transformer (303) which is undesirable so by the best mode for carrying out of the invention a transformer (303) with 1:1 turn's ratio is used.
  • the operating frequency of the inverter (302) has to be synchronized to the resonant frequency of the resonant circuit (201) to obtain maximal voltage multiplication and maximal power transfer.
  • This task is accomplished by driving the voltage controlled oscillator (VCO) (405) from a phase detector (406).
  • the phase detector compares the zero crossings of the inductor current (502) with moments of switching of the inverter. If a difference is detected, the control voltage of the VCO (405) is adjusted to minimize the phase mismatch.
  • a resistive shunt (414) is used for current sensing and a comparator (407) detects the polarity of the shunt voltage, proportional to the current.
  • Alternative solution with current transformer may be preferable for large currents.
  • Frequency shifting is accomplished by calculating the power delivered to the resonant circuit (201) through an analog multiplier (409), multiplying the input voltage (501) and the input current (502) of the resonant circuit (201). The obtained instantaneous power signal is compared to a reference value through an error amplifier (408) to regulate the power. The output of the amplifier (408) overrides the VCO's (405) command signal from the phase detector and increases the operating frequency until the required mean power is achieved. Reduction of frequency could also be used for power reduction but this leads to increased switching losses in the resonant inverter (302) so it is not considered by the best mode for carrying out of the invention.
  • multiplying the resonant circuit (201) output voltage and output current could be used for power estimation. This way the power estimation is not falsified by losses in the resonant circuit (201), but as the output current is much distorted and out of phase, this was not an acceptable approach by this best mode for carrying out of the invention.
  • the described regulation has a tendency to raise the output voltage of the resonant circuit (201) to an unacceptable level if the load is disconnected.
  • a feedback circuit (306) can sense the output voltage, compare it to a reference value through an error amplifier (410) and override the VCO's (405) command signal to move the inverter (302) out of resonance.
  • the input current (502) of the resonant circuit (201) is detected with an absolute value circuit (411). This is an acceptable alternative as by limited range of frequency shift, defined by the VCO (405), the voltage of the resonant capacitor (203) is approximately proportional to the capacitor current.
  • the output power P C0R the equivalent load resistance (413) and the operating resonant frequency have to be defined.
  • the required capacitance of the resonant capacitor (203) is calculated from the formula:
  • the capacitor (203) voltage is equal to the voltage between the electrodes (104 and 105) of the corona treating station (103), usual values are about 10 kV rms. There are no standard capacitors available for the required breakdown voltage and capacitance but by series connection of commercial, low voltage or medium voltage units, the required capacitor (203) can be easily constructed.
  • the inductance of the inductor (202) has to be:
  • the inductor (202) has to be designed for the following current:
  • the inductor (202) voltage is approximately equal to the capacitor voltage as the input voltage of the resonant circuit (201) can be neglected in comparison with the output voltage.
  • the inductor (202) can be constructed by series connection of several low voltage or medium voltage inductors (601 to 6On), as shown in Fig. 6. In this case, inductors with ferrite core are applicable.
  • the inductor (202) is constructed as a segmented cylindrical winding with air core.
  • the radial cross section of this implementation is shown in Fig. 7(a).
  • the winding (703) is placed on brushes (702) fixed on a cylindrical holder (704).
  • the form of the brush (702) is shown in Fig 7(b).
  • Air gap (704) between the holder (704) and the winding (703) enhances cooling.
  • the conductor for winding (703) has to be stranded from several mutually insulated conductors to minimize eddy current losses.
  • the total inductor (202) voltage is divided to a sufficient number of segments, no special insulation enhancements, as layer insulation or oil bath, are necessary.
  • AU parts of the proposed electronic generator (101) and the resonant voltage multiplier (201) can be constructed with standard industrial procedures.
  • the treater apparatus constructed by use of the described electronic generator (101) followed by resonant circuit (201) multiplier is suitable for the surface treatment of any standard materials.
  • Similar efficiency and similar volume of the proposed generator (101) with resonant circuit (201) can be achieved as by the combination of electronic generator (101) with a high voltage transformer (102).
  • Design and manufacturing of the resonant inductor ((202) is easier than the design and manufacturing of the appropriate high voltage transformer (102).
  • the use of the transformer insulation oil, which is a hazardous material, is avoided.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

An electronic generator (101) produces oscillations which are applied through a resonant circuit (201) to the electrodes (104 and 105) of a corona surface treating station (103). It includes a rectifier (301), with or without active power factor correction capability, which transforms a.c. electric power from mains to a d.c. power and a resonant inverter (302), which transforms the obtained d.c. power to a medium frequency a.c. power. The required voltage multiplication is achieved by a resonant circuit (201) comprising one inductor (202) and one capacitor (203). The operating frequency of the resonant inverter (302) is synchronized to the resonant frequency of the inductor-capacitor connection by a phase locked loop circuit (304) based on sensing the input current to the resonant circuit (201). A power feedback circuit (305) measures the average power delivered to the treater and corrects the operating frequency of the inverter (302) to adjust power for treatment to the required level. A voltage feedback circuit (306) measures the output voltage of the treater and shifts the operating frequency of the inverter (302) out of resonance to avoid overload conditions.

Description

CORONA DISCHARGE TREATER WITH RESONANT VOLTAGE MULTIPLICATION
Technical Field
The field of invention is apparatus for treating the surface of polymer and other film materials with a high voltage gaseous discharge called corona. The treatment of conductive and non-conductive materials is a well established process to enhance their adhesion to printing inks and glues. The sheet or web of the material is conveyed over a metal roller which forms one electrode of the treater. The other electrode is on a small distance from the metal roller and runs parallel with its axis.
Medium frequency, high voltage signal is applied across the electrodes. A corona discharge is initiated in the air gap between the electrodes. Free electrons and ions, accelerated by the intensive electric field in the air gap, bombards the surface of the material involved in the treatment and produces physical and chemical changes on its surface. The intensity of treatment is adjusted depending on the level of the adhesion problem.
Background Art
Apparatus for carrying out corona treatment are described in U. S. Pat. Nos. 3,133,193; 3,507,763; 3,662,169; 3,708,733; 3,817,701; 3,900,358; 3,973,132; 4,051,044; 4,423,461; 4,644,457; 5,486,993 and other. A principal block diagram of industrial corona treaters is shown in Fig. 1. All known solutions produce the high voltage required for treatment, by use of a transformer (102) with high voltage secondary.
The transformer's primary is supplied from an appropriately regulated electronic generator (101). Corona is formed between the electrodes (104 and 105) in the treating station (103). The required voltage between the electrodes (104 and 105) is about 10 kV rms., its frequency can be from some kHz to some 10 kHz. By modern treaters frequencies in the 20 kHz to 50 kHz frequency range are preferable.
Design and manufacturing of transformers for corona treaters with high voltage secondary requires special care. To enhance the insulation of the high-voltage winding and to improve cooling, usually the transformer is immersed in oil bath.
Disclosure of the Invention
The present invention replaces the high voltage transformer used by corona treaters with a resonant circuit comprising a high voltage inductor and a high voltage capacitor. An electronic generator supplies the resonant circuit at its resonant frequency or near to the resonant frequency. The high voltage required for treatment is generated by voltage multiplication in the resonant circuit.
The high voltage inductor is divided into segments to easily withstand high voltage. The capacitor is constructed by series connection of medium voltage units. This way the design and manufacturing of the a.c. voltage multiplication is simplified, compared to the traditional implementation with transformer.
The electronic generator is a mains rectifier followed by a resonant inverter. The inverter is synchronized to the resonant frequency of the inductor-capacitor network by a phase locked loop circuit. A power feedback circuit calculates the output power of the electronic generator and corrects the operating frequency of the inverter to adjust the power for treatment to the required level. A voltage feedback circuit measures the output voltage of the voltage multiplier and corrects the operating frequency of the inverter to avoid overload conditions. The treater constructed by use of electronic generator followed by resonant circuit is suitable for the treatment of any standard materials. Similar efficiency and similar volume of the proposed generator with resonant circuit can be achieved as by the combination of electronic generator with high voltage transformer. Design and manufacturing of the high voltage transformer is replaced by a simpler design and manufacturing of a high voltage inductor. The required capacitor can be combined from standard low voltage or medium voltage units. Oil bath for transformer insulation and cooling is eliminated by resonant circuit voltage multiplication.
Brief Description of Drawings
Fig. 1 is a block diagram explaining the prior art. The electronic generator supplies the treating station through a transformer with high- voltage secondary winding.
Fig. 2 is the block diagram of the solution of the treater system proposed by this invention. The electronic generator supplies the treating station through an LC resonant circuit.
Fig. 3 is the block diagram of the electronic generator from Fig. 2, suitable for driving the resonant circuit.
Fig. 4 shows a more detailed block diagram of the electronic generator from Fig. 2 and Fig. 3, together with the resonant circuit and the treating station model.
Fig. 5 shows typical waveforms of voltages and currents of the electronic generator and the resonant circuit.
Fig. 6 shows one possible implementation of the high voltage inductor by series connection of low voltage or medium voltage inductors with ferrite cores.
Fig. 7 shows a second possible implementation of the high voltage inductor as a segmented air cored winding.
Best Mode for Carrying out of the Invention
The proposed solution for carrying out corona treatment is shown in Fig. 2. The electronic generator (101) supplies the electrodes (104 and 105) of the treating station (103) through a resonant circuit (201). The generator is supplied from one phase or three phase, low voltage distribution network. The required voltage multiplication is achieved by the resonant circuit (201) comprising a high voltage inductor (202) and a high voltage capacitor (203). The voltage multiplication obtained by resonant circuit is on similar level as the multiplication by transformer (102) in the prior art shown in Fig. 1.
Block diagram of the electronic generator (101) suitable to drive the resonant circuit (201) is shown in Fig. 3. The high voltage transformer (102) is eliminated, but a 1:1 transformer (303) is necessary to isolate the treating station (103) from the mains. If the transformer (303) is at the input of the electronic generator, it has to be designed for the mains frequency. If the transformer (303) is at the output of the generator, it is designed for the operating frequency of the electronic generator (Λ Λ1 ^A^ =r- m ' ~~~
The power circuit of the electronic gen*-* ~. Ji v— -/ -- ' ^
(301 and 302). The rectifier (301) can be a simple, unregulated diode circuit. For higher power levels an active power factor correction (PFC) rectifier is preferable. The transformer (303) with 1:1 turn's ratio is connected to the output of the inverter. This position of the transformer (303) is preferable as a small size ferrite core device can be used thanks to the high operating frequency of the inverter.
A more detailed circuit diagram of the best mode of carrying out the electronic generator (101) completed with the resonant voltage multiplier circuit (201) and the model (404) of the treating station (103) is shown in Fig. 4. The loading effect of the treating station (103) in the actual operating point is represented with parallel connection of the parasitic capacitance (412) of the electrodes (104 and 105) and the equivalent load resistance (413). The equivalent load resistance (413) is calculated from the required corona power and corona voltage as:
Figure imgf000004_0001
The inverter (302) operates in square wave mode, generating pulses (501) of alternating polarity with amplitude equal to the rectified voltage V1n , as shown in Fig. 5.
The operating frequency of the inverter (302) is equal to the frequency of resonance of the resonant circuit (201) or it is near to it. Thanks to the filtering effect of the resonant circuit (201), the inductor (202) current (502) is approximately sinusoidal.
The voltage multiplication factor of the resonant circuit (201) with the equivalent load (404) of the treating station (103), but without considering the losses in the resonant inductor (202) and resonant capacitor (203) is:
Figure imgf000004_0002
where the resonant frequency f0 is: f _ ωo _ 1
2nJLrCr and the loaded quality factor of the resonant circuit is:
QL = &oCrRcoR •
In the given formulae the parasitic capacitance (412) of the treating station is incorporated in the resonant capacitor (203) to simplify the calculations
The voltage multiplication factor has its maximal value at the frequency: f -f fix which is near to the resonant frequency fo by high values of the loaded quality factor QL . The maximal value is calculated by use of formula:
Figure imgf000004_0003
Usual value of Q1 by corona treaters is 30 and higher. Losses in the resonant inductor (202) and the resonant capacitor (203) lead to the lowering of the voltage multiplication factor of the resonant circuit (201) and to lowering of the transmitted power, but acceptable results can be achieved by careful design of the resonant inductor (202) and careful choice of the resonant capacitor (203).
The power components of the rectifier-inverter cascade (301 and 302) driving the resonant circuit (201) are explained in the further text by use of Fig. 4.. An electromagnetic interference (EMI) filter (401) is necessary at the input to moderate the disturbances feed back to the mains. By the best mode for carrying out of the invention, the single phase rectifier bridge (402) is combined with a boost stage (403) with power factor correction (PFC) capability. This way not only near unity power factor is achieved, but the rectified voltage Vn, is regulated to a constant average value, so the operation of the inverter is with less perturbations. In case of corona treaters over several kW-s, a three phase rectifier, also with PFC, is preferable.
The resonant inverter (302) is of bridge type, comprising four power MOSFETs or IGBT switches (404). The switches are turned on and off in diagonal pairs for one half of the switching period. This way a square wave voltage, driving the isolation transformer (303) is generated. The transformer (303) transmits the square voltage to the input of the resonant multiplier (201) without significant change of amplitude or distortion of waveform. A transformer (303) with some voltage boost would be convenient to minimize resonant circuit (201) size but this usually leads to parasitic resonances in the transformer (303) which is undesirable so by the best mode for carrying out of the invention a transformer (303) with 1:1 turn's ratio is used.
The operating frequency of the inverter (302) has to be synchronized to the resonant frequency of the resonant circuit (201) to obtain maximal voltage multiplication and maximal power transfer. This task is accomplished by driving the voltage controlled oscillator (VCO) (405) from a phase detector (406). The phase detector compares the zero crossings of the inductor current (502) with moments of switching of the inverter. If a difference is detected, the control voltage of the VCO (405) is adjusted to minimize the phase mismatch.
By the best mode for carrying out of the invention described here, a resistive shunt (414) is used for current sensing and a comparator (407) detects the polarity of the shunt voltage, proportional to the current. Alternative solution with current transformer may be preferable for large currents.
In resonance, maximal power is transmitted to the treating station (103). Some frequency shift can be used to regulate the transmitted power to a lower level if the actual treatment requires that. Frequency shifting is accomplished by calculating the power delivered to the resonant circuit (201) through an analog multiplier (409), multiplying the input voltage (501) and the input current (502) of the resonant circuit (201). The obtained instantaneous power signal is compared to a reference value through an error amplifier (408) to regulate the power. The output of the amplifier (408) overrides the VCO's (405) command signal from the phase detector and increases the operating frequency until the required mean power is achieved. Reduction of frequency could also be used for power reduction but this leads to increased switching losses in the resonant inverter (302) so it is not considered by the best mode for carrying out of the invention.
Alternatively, multiplying the resonant circuit (201) output voltage and output current could be used for power estimation. This way the power estimation is not falsified by losses in the resonant circuit (201), but as the output current is much distorted and out of phase, this was not an acceptable approach by this best mode for carrying out of the invention.
The described regulation has a tendency to raise the output voltage of the resonant circuit (201) to an unacceptable level if the load is disconnected. To avoid this type of overload, a feedback circuit (306) can sense the output voltage, compare it to a reference value through an error amplifier (410) and override the VCO's (405) command signal to move the inverter (302) out of resonance. In the best mode for carrying out of the invention instead of detection of the output voltage, the input current (502) of the resonant circuit (201) is detected with an absolute value circuit (411). This is an acceptable alternative as by limited range of frequency shift, defined by the VCO (405), the voltage of the resonant capacitor (203) is approximately proportional to the capacitor current. To design the components of the resonant circuit (201), the output power PC0R , the equivalent load resistance (413) and the operating resonant frequency have to be defined. The required capacitance of the resonant capacitor (203) is calculated from the formula:
Figure imgf000006_0001
The capacitor (203) voltage is equal to the voltage between the electrodes (104 and 105) of the corona treating station (103), usual values are about 10 kV rms. There are no standard capacitors available for the required breakdown voltage and capacitance but by series connection of commercial, low voltage or medium voltage units, the required capacitor (203) can be easily constructed.
The inductance of the inductor (202) has to be:
Figure imgf000006_0002
The inductor (202) has to be designed for the following current:
1LRMS ~ 24Ϊ ' vm ■
The inductor (202) voltage is approximately equal to the capacitor voltage as the input voltage of the resonant circuit (201) can be neglected in comparison with the output voltage.
There are no commercially available inductors for the given requirements. The inductor (202) can be constructed by series connection of several low voltage or medium voltage inductors (601 to 6On), as shown in Fig. 6. In this case, inductors with ferrite core are applicable.
By the best mode for carrying out of the invention the inductor (202) is constructed as a segmented cylindrical winding with air core. The radial cross section of this implementation is shown in Fig. 7(a). The winding (703) is placed on brushes (702) fixed on a cylindrical holder (704). The form of the brush (702) is shown in Fig 7(b). Air gap (704) between the holder (704) and the winding (703) enhances cooling. By design of resonant inductor (202) for higher power, the conductor for winding (703) has to be stranded from several mutually insulated conductors to minimize eddy current losses. As the beginning of the inductor (202) is far from its end, and the total inductor (202) voltage is divided to a sufficient number of segments, no special insulation enhancements, as layer insulation or oil bath, are necessary.
Industrial Applicability
AU parts of the proposed electronic generator (101) and the resonant voltage multiplier (201) can be constructed with standard industrial procedures. The treater apparatus constructed by use of the described electronic generator (101) followed by resonant circuit (201) multiplier is suitable for the surface treatment of any standard materials. Similar efficiency and similar volume of the proposed generator (101) with resonant circuit (201) can be achieved as by the combination of electronic generator (101) with a high voltage transformer (102). Design and manufacturing of the resonant inductor ((202) is easier than the design and manufacturing of the appropriate high voltage transformer (102). The use of the transformer insulation oil, which is a hazardous material, is avoided.

Claims

1. A power supply for corona discharge surface treater in which the material to be treated is disposed between two metallic electrodes, characterized by comprising a rectifier circuit for converting a.c. input to a d.c. output with active power factor correction capability or without it, comprising an inverter circuit coupled to receive the output of the rectifier circuit and generating a square wave a.c. output, comprising an isolation transformer transmitting the inverter output without significant change in amplitude and waveform, comprising a resonant circuit receiving the transformer output voltage and increasing its amplitude to the level required by the treating station and changing its waveform to approximately sinusoidal, and comprising a feedback circuit receiving signals that indicate the voltage and current supplied to the corona treating station and controlling the operating frequency of the inverter.
2. A power supply as recited in 1, characterized by synchronizing the operating frequency of the inverter to the resonant frequency of the resonant circuit to obtain maximal increase in voltage level and maximal power transfer to the treating station.
3. A power supply as recited in 1, characterized by minor changes in the operating frequency of the inverter from the synchronized case given in 2, to adjust the voltage increase and power transfer to a lower level required by the actual treatment.
4. A power supply as recited in 1, characterized by means to limit the output voltage of the resonant circuit to a safe level if the regulation stated in 2 and 3 fails to limit the voltage.
PCT/RS2008/000004 2008-01-18 2008-01-18 Corona discharge treater with resonant voltage multiplication WO2009091273A1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016189666A (en) * 2015-03-30 2016-11-04 株式会社東芝 Power supply circuit for driving surface discharge element
JP7011118B1 (en) * 2021-08-11 2022-01-26 京都電機器株式会社 Pulse power supply for plasma processing equipment

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1275523A (en) * 1969-04-14 1972-05-24 Pillar Corp Corona discharge plastics treater apparatus
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DE4235766C1 (en) * 1992-10-24 1994-05-05 Agrodyn Hochspannungstechnik G Corona generator having two resonant circuits - automatically adjusts to match electrical properties of materials under treatment
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