WO2005106904A1 - Capacitor and device for electric pulse modulation with such capacitor - Google Patents

Capacitor and device for electric pulse modulation with such capacitor Download PDF

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Publication number
WO2005106904A1
WO2005106904A1 PCT/SE2005/000630 SE2005000630W WO2005106904A1 WO 2005106904 A1 WO2005106904 A1 WO 2005106904A1 SE 2005000630 W SE2005000630 W SE 2005000630W WO 2005106904 A1 WO2005106904 A1 WO 2005106904A1
Authority
WO
WIPO (PCT)
Prior art keywords
capacitor
dielectric
explosive
voltage
permittivity
Prior art date
Application number
PCT/SE2005/000630
Other languages
French (fr)
Inventor
Anders Larsson
Torgny Carlsson
Original Assignee
Totalförsvarets Forskningsinstitut
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Totalförsvarets Forskningsinstitut filed Critical Totalförsvarets Forskningsinstitut
Publication of WO2005106904A1 publication Critical patent/WO2005106904A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G2/00—Details of capacitors not covered by a single one of groups H01G4/00-H01G11/00
    • H01G2/14—Protection against electric or thermal overload
    • H01G2/16—Protection against electric or thermal overload with fusing elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/13—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material current responsive
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G7/00—Capacitors in which the capacitance is varied by non-mechanical means; Processes of their manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G7/00—Capacitors in which the capacitance is varied by non-mechanical means; Processes of their manufacture
    • H01G7/06—Capacitors in which the capacitance is varied by non-mechanical means; Processes of their manufacture having a dielectric selected for the variation of its permittivity with applied voltage, i.e. ferroelectric capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
    • H01H9/54—Circuit arrangements not adapted to a particular application of the switching device and for which no provision exists elsewhere

Definitions

  • the invention relates to a capacitor with changeable dielectric properties, and a device for electric pulse modulation comprising such a capacitor, for instance an HPM source (High-Power Microwave, high-power microwave radiation) or a high- voltage switchgear.
  • HPM source High-Power Microwave, high-power microwave radiation
  • high- voltage switchgear High-voltage switchgear
  • a capacitor can be charged to a certain capacitor voltage U and to a certain capacitor charge Q.
  • the capacitance of a capacitor is in turn dependent on the physical appearance of the capacitor and the dielectric material that fills the capacitor. By choosing the physical design and dielectric materials, the electric properties of a capacitor can be varied in a large range.
  • a capacitor is a central component in electric circuits and in a pulse modulator where it is desirable to quickly change the shape of an electric pulse.
  • a high voltage pulse is desirable is in an HPM source (High-Power Microwave, high- power microwave radiation) where the purpose is to generate microwave radiation that can knock out electronic equipment.
  • HPM source High-Power Microwave, high- power microwave radiation
  • a voltage dip is desirable is in a switch that requires the current to be momentarily zero.
  • Prior-art capacitors are based on the fact that their properties are kept constant. A large number of other components are necessary in the circuit for the desirable pulse modulation to be provided. As a result, the systems are large and heavy. In order to create a compact pulse modulator it would be desirable to integrate several functions in the same component.
  • the invention solves the above problems of a capacitor whose dielectric properties are quickly changed. According to the invention, this is achieved by the dielectric of the capacitor comprising an explosive which detonates, as claimed in the claims.
  • the invention will in the following be described in more detail with reference to the accompanying Figures.
  • Fig. 1 shows a capacitor according to prior-art technique.
  • Fig. 2 shows a capacitor according to the invention.
  • Fig. 3 shows a first embodiment of the invention.
  • Fig. 4 shows a second embodiment of the invention.
  • Fig. 5 shows an HPM source with a capacitor according to the invention.
  • Fig. 6 shows a switch with a capacitor according to the invention.
  • Fig. 1 shows a capacitor according to prior-art technique, here illustrated as a plate capacitor.
  • the electrodes (1, 2) are separated by a dielectric material (3) with a given relative permittivity ( ⁇ ⁇ ) and a given electric conductivity ( ⁇ ).
  • the conductivity is in the normal case negligible, and the relative permittivity determines the capacitance of the capacitor.
  • the principle of a capacitor is that the capacitor charge Q is equal to the product of the capacitance C of the capacitor and the voltage across the capacitor TJ.
  • the capacitor charge Q is constant. If the capacitance C is changed, thus also the voltage Uis changed. This means that if the capacitance is quickly decreased/increased, an increase/decrease of the voltage across the capacitor is provided.
  • Figs 2a-c show a capacitor according to the invention.
  • the invention is here shown as a plate capacitor with electrodes (1, 2) and a dielectric (3) with dielectric properties ( ⁇ Sr,bef o re, O efore), but the invention can also be used in other types of capacitors.
  • a dielectric that can be made to detonate.
  • the dielectric comprises an explosive.
  • the dielectric can, wholly or partly, consist of an explosive, or for instance an inert dielectric doped with an explosive can be used.
  • the dielectric detonates the dielectric properties of the material are changed after the detonation front (4) to the properties of the residual products/gases (Rafter, cr a ft er )- Two different function modes can here be used.
  • Figs 3a-c show a first embodiment of the invention with electrodes (1, 2), the original dielectric (3) and a residual gas (4). If the electric conductivity of the residual gases (Rafter) is negligible, a voltage amplification across the capacitor is obtained according to the following analysis using a plate capacitor as an example.
  • Fig. 5 shows an application of the first embodiment.
  • the voltage source (10) charges the capacitor (12) via the charging resistor (11). When the capacitor has been charged, it is made to detonate and thus amplify the voltage. At the required point of time, a shutter (13) is then operated, and the voltage commutes across the load (14) here exemplified by an HPM source.
  • Fig. 6 shows an application of the second embodiment, here in the form of a switch.
  • the voltage source (10) feeds the load (15) via the charging resistor (11) and the switch (13). For the switch (13) to be opened, the current must be close to zero. By letting the capacitor (12) detonate, the voltage across the load is lowered, and as this voltage approaches zero, the switch (13) can be opened.
  • the invention is here shown as a capacitor comprising two electrodes (1, 2) spaced from each other by a dielectric (3) comprising an explosive.
  • a dielectric (3) comprising an explosive.
  • the permittivity of the residual gases is lower than that of the explosive.
  • the electric conductivity of the residual gases is either good or poor. Poor conductivity means that the reduced permittivity gives a voltage amplification across the capacitor. Good conductivity means that the residual gas is short circuited, thus resulting in a voltage reduction across the capacitor.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
  • Air Bags (AREA)

Abstract

The invention relates to a capacitor with changeable dielectric properties, and a device for electric pulse modulation comprising such a capacitor, for instance an HPM source (High-Power Microwave, high-power microwave radiation). The invention is shown as a capacitor comprising two electrodes (1, 2) spaced from each other by a dielectric (3) comprising an explosive. When the explosive detonates/has detonated, it gives rise to residual products (4) with new dielectric properties. The permittivity of the residual gases is lower than that of the explosive. Depending on the field of application, the electric conductivity of the residual gases is either good or poor. Poor conductivity means that the reduced permittivity gives a voltage amplification across the capacitor. Good conductivity means that the residual gas is short circuited, thus resulting in a voltage reduction across the capacitor.

Description

CAPACITOR AND DEVICE FOR ELECTRIC PULSE MODULATION WITH SUCH CAPACITOR
The invention relates to a capacitor with changeable dielectric properties, and a device for electric pulse modulation comprising such a capacitor, for instance an HPM source (High-Power Microwave, high-power microwave radiation) or a high- voltage switchgear.
A capacitor can be charged to a certain capacitor voltage U and to a certain capacitor charge Q. The ratio of the charge Q to the voltage U defines the capacitance C of the capacitor as follows: c = g
The capacitance of a capacitor is in turn dependent on the physical appearance of the capacitor and the dielectric material that fills the capacitor. By choosing the physical design and dielectric materials, the electric properties of a capacitor can be varied in a large range.
A capacitor is a central component in electric circuits and in a pulse modulator where it is desirable to quickly change the shape of an electric pulse. One example where a high voltage pulse is desirable is in an HPM source (High-Power Microwave, high- power microwave radiation) where the purpose is to generate microwave radiation that can knock out electronic equipment. A further example where a voltage dip is desirable is in a switch that requires the current to be momentarily zero.
Prior-art capacitors are based on the fact that their properties are kept constant. A large number of other components are necessary in the circuit for the desirable pulse modulation to be provided. As a result, the systems are large and heavy. In order to create a compact pulse modulator it would be desirable to integrate several functions in the same component.
The invention solves the above problems of a capacitor whose dielectric properties are quickly changed. According to the invention, this is achieved by the dielectric of the capacitor comprising an explosive which detonates, as claimed in the claims. The invention will in the following be described in more detail with reference to the accompanying Figures.
Fig. 1 shows a capacitor according to prior-art technique. Fig. 2 shows a capacitor according to the invention.
Fig. 3 shows a first embodiment of the invention.
Fig. 4 shows a second embodiment of the invention.
Fig. 5 shows an HPM source with a capacitor according to the invention.
Fig. 6 shows a switch with a capacitor according to the invention.
Fig. 1 shows a capacitor according to prior-art technique, here illustrated as a plate capacitor. The electrodes (1, 2) are separated by a dielectric material (3) with a given relative permittivity (ετ) and a given electric conductivity (σ). The conductivity is in the normal case negligible, and the relative permittivity determines the capacitance of the capacitor. The principle of a capacitor is that the capacitor charge Q is equal to the product of the capacitance C of the capacitor and the voltage across the capacitor TJ.
Q = C -U
For a charged capacitor, the capacitor charge Q is constant. If the capacitance C is changed, thus also the voltage Uis changed. This means that if the capacitance is quickly decreased/increased, an increase/decrease of the voltage across the capacitor is provided.
Figs 2a-c show a capacitor according to the invention. The invention is here shown as a plate capacitor with electrodes (1, 2) and a dielectric (3) with dielectric properties (<Sr,before, O efore), but the invention can also be used in other types of capacitors. In order to quickly change the dielectric properties of the dielectric, use is made of a dielectric that can be made to detonate. The dielectric comprises an explosive. The dielectric can, wholly or partly, consist of an explosive, or for instance an inert dielectric doped with an explosive can be used. When the dielectric detonates, the dielectric properties of the material are changed after the detonation front (4) to the properties of the residual products/gases (Rafter, crafter)- Two different function modes can here be used.
Figs 3a-c show a first embodiment of the invention with electrodes (1, 2), the original dielectric (3) and a residual gas (4). If the electric conductivity of the residual gases (Rafter) is negligible, a voltage amplification across the capacitor is obtained according to the following analysis using a plate capacitor as an example. A plate capacitor has the capacitance: C = 0 .er -
where SQ is the permittivity of vacuum, εr is the relative permittivity of the dielectric, A is the electrode area and c?is the gap distance of the capacitor. To achieve a voltage amplification, the relative permittivity is changed so that the permittivity before is greater than the permittivity after, i.e. εr> before > afler- This results in a voltage amplification: after _ fcr, before before r, after
Figs 4a-c show a second embodiment of the invention with electrodes (1, 2) and the original dielectric (3). If the electric conductivity of the residual gases (σafter) is good, a short circuit is in practice obtained over the residual gases (4), which can be represented by two partial capacitances in series. By good conductivity is here meant that the relaxation time τ = εr>after / σafter is shorter than the time scale for the change of the dielectric properties. A decrease of the voltage across the capacitor is given according to the following analysis using a plate capacitor as an example. When the conductivity of the residual gases is good, the area is short circuited by residual gases (4), and the remaining capacitance proceeds to infinity as the detonation front approaches the electrodes (1, 2), which is given by the gap distance (d) proceeding to zero. As the capacitance approaches infinity, the voltage across the capacitor approaches zero.
Which of these two function modes occurs is determined by the material properties of the dielectric.
Fig. 5 shows an application of the first embodiment. The voltage source (10) charges the capacitor (12) via the charging resistor (11). When the capacitor has been charged, it is made to detonate and thus amplify the voltage. At the required point of time, a shutter (13) is then operated, and the voltage commutes across the load (14) here exemplified by an HPM source. Fig. 6 shows an application of the second embodiment, here in the form of a switch. The voltage source (10) feeds the load (15) via the charging resistor (11) and the switch (13). For the switch (13) to be opened, the current must be close to zero. By letting the capacitor (12) detonate, the voltage across the load is lowered, and as this voltage approaches zero, the switch (13) can be opened.
The invention is here shown as a capacitor comprising two electrodes (1, 2) spaced from each other by a dielectric (3) comprising an explosive. When the explosive detonates/has detonated, it gives rise to residual products (4) with other dielectric properties. The permittivity of the residual gases is lower than that of the explosive. Depending on the field of application, the electric conductivity of the residual gases is either good or poor. Poor conductivity means that the reduced permittivity gives a voltage amplification across the capacitor. Good conductivity means that the residual gas is short circuited, thus resulting in a voltage reduction across the capacitor.

Claims

1 A capacitor comprising a dielectric (3) with dielectric properties (£r,before, before), c h a r a c t e r i s e d in that the dielectric (3) comprises an explosive.
2. A capacitor as claimed in claim 1, wherein the explosive in detonation gives rise to residual products (4) with new dielectric properties.
3. A capacitor as claimed in claim 2, wherein the permittivity (<?r,after) of the residual products is smaller than the permittivity (^before) of the dielectric before detonation, that is (<5r,before Rafter).
4. A capacitor as claimed in claim 2 or 3, wherein the electric conductivity (cFafter) of the residual products is good.
5. A capacitor as claimed in claim 3 or 4, wherein the electric conductivity (cTafter) of the residual products provides a short circuit.
6. A capacitor as claimed in claim 3 or 4, wherein the electric conductivity (oafter) of the residual products provides a voltage amplification.
7. A capacitor as claimed in any one of claims 1-6, wherein the dielectric comprises a dielectric substance doped with an explosive.
8. A capacitor as claimed in any one of claims 1-7, wherein the capacitor comprises two electrodes (1, 2) separated by the dielectric (3).
9. A device for electric pulse modulation, wherein the device comprises a capa- citor as claimed in any one of claims 1 -8.
10. A device as claimed in claim 9, wherein the device comprises a source for electromagnetic radiation (14).
11. A device as claimed in claim 9, wherein the device comprises a switch (13).
PCT/SE2005/000630 2004-04-29 2005-04-29 Capacitor and device for electric pulse modulation with such capacitor WO2005106904A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0401102A SE527701C2 (en) 2004-04-29 2004-04-29 Capacitor with changeable dielectric properties and device for electrical pulse modulation with such capacitor
SE0401102-9 2004-04-29

Publications (1)

Publication Number Publication Date
WO2005106904A1 true WO2005106904A1 (en) 2005-11-10

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WO (1) WO2005106904A1 (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3586743A (en) * 1965-05-04 1971-06-22 Philippe F Van Eeck Process for making solid state current limiters and other solid state devices
US5771148A (en) * 1995-11-17 1998-06-23 Motorola, Inc. Intercalation-based voltage variable capacitor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3586743A (en) * 1965-05-04 1971-06-22 Philippe F Van Eeck Process for making solid state current limiters and other solid state devices
US5771148A (en) * 1995-11-17 1998-06-23 Motorola, Inc. Intercalation-based voltage variable capacitor

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Publication number Publication date
SE527701C2 (en) 2006-05-16
SE0401102L (en) 2005-10-30
SE0401102D0 (en) 2004-04-29

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