SE527701C2 - Capacitor with changeable dielectric properties and device for electrical pulse modulation with such capacitor - Google Patents

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

The invention will be described in more detail below with reference to the accompanying figures: Fig. 1 shows a capacitor according to the prior art 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 the prior art, illustrated here as a plate capacitor. The electrodes (1,2) are separated by a dielectric material (3) with a given relative permittivity (ef) and a given electrical conductivity (o).

The conductivity is normally 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 U.

Q = c-U For a charged capacitor, the capacitor charge Q is constant. Thus, if the capacitance C changes, so does the voltage U. This means that if the capacitance decreases / increases rapidly, an increase / decrease of the voltage across the capacitor is achieved.

Figures 2a-c show a capacitor according to the invention. The invention is shown here as a plate capacitor with electrodes (1,2) and dielectric (3) with dielectric properties (snföm om), but the invention can also be used in other types of capacitors. To quickly change the dielectric properties of the dielectric, a dielectric that can be detonated is used. The dielectric comprises either an explosive or an inert dielectric doped with explosive. As the dielectric detonates, the dielectric properties of the material after the detonation front (4) change to the properties of the residual products / gases (the stone them).

Here, two different function modes can be used. " a 3 Figure 3a-c shows a first embodiment of the invention with electrodes (1, 2) originally dielectric (3) and residual gas (4). If the electrical conductivity of the residual gases (crew) is negligible, a voltage gain across the capacitor is obtained according to the following analysis with a plate capacitor as an example. A plate capacitor has the capacitance: C = g0.gr.å d where so is the permittivity of vacuum, s, is the relative permittivity of the dielectric, A is the electrode area and d is the gap distance in the capacitor. In order to obtain a voltage amplification, the relative pennivity is changed so that the permittivity before is greater than the permittivity after, ie. sm ",> em". This gives a voltage gain of: Uefrer _ SfM / bre Ume fre / ur Figure 4a-c shows a second embodiment of the invention with electrodes (1,2) and original dielectric (3). If the electrical conductivity of the residual gases (oem) is good, a short circuit across the residual gases (4) is obtained in practice, which can be represented by two sub-capacitances in series. Voltage reduction across the capacitor is given according to the following analysis with a plate capacitor as an example. Since the conductivity of the residual gases is good, the area with residual gases (4) is short-circuited and the remaining capacitance goes towards infinity as the detonation front approaches the electrodes (1,2), which is given by the gap distance (d) approaching zero. As the capacitance approaches infinity, the voltage across the capacitor approaches zero.

Which of these two modes of operation occurs is determined by the material properties of the dielectric.

Figure 5 shows an application of the first embodiment. The voltage source (10) charges the capacitor (12) via the charging resistor (11). When the capacitor is charged, it is caused to detonate and thereby amplify the voltage. At the desired time, a shutter (13) is then closed and the voltage commutates over the load (14) here exemplified by an HPM source.

Figure 6 shows an application of the second embodiment, here in the form of a switch. The voltage source (10) supplies the load (15) via the charging resistor (11) and the switch (13). In order for the switch (13) to be able to be opened, the current must be close to zero. By letting the capacitor (12) detonate, the voltage across the load is lowered and when this voltage approaches zero, the switch (13) can be opened.

The invention is shown as a capacitor comprising two electrodes (1,2) separated by a dielectric (3) comprising an explosive. When the explosive detonates / has detonated, it gives rise to residual products (4) with other dietetic properties.

The permittivity of the residual gases is lower than that of the explosive. Depending on the area of use, the electrical conductivity of the residual gases is slightly good or poor. Poor conductivity means that the reduced permittivity results in a voltage gain across the capacitor. Good conductivity means that the residual gas is short-circuited and the effect is a voltage reduction across the capacitor.

Claims (10)

10 15 20 25 30 35 527 701 PATENT REQUIREMENTS Capacitor comprising a dielectric (3) with dielectric properties (anwa orm) that are changeable, characterized in that the dielectric (3) comprises an explosive. Capacitor according to Claim 1, characterized in that the explosive during a detonation gives rise to residual products (4) with new dielectric properties. Capacitor according to Claim 2, characterized in that the permittivity (sne fl ef) of the residual products is less than the permittivity (snfme) of the dielectric before the detonation, i.e. (afmæefßftef). 4. A capacitor according to claim 3, characterized in that the electrical conductivity (oem) of the residual products causes a short circuit. Capacitor according to Claim 3, characterized in that the electrical conductivity (oem) of the residual products produces a voltage amplification. A capacitor according to any one of the preceding claims, characterized in that the dielectric comprises a dielectric substance doped with explosive. A capacitor according to any one of claims 1-6, characterized in that the capacitor comprises two electrodes (1,2) separated by the dielectric (3). Device for electrical pulse modulation, characterized in that the device comprises a capacitor according to any one of claims 1-7. Device according to claim 8, characterized in that the device comprises a source of electromagnetic radiation (14). Device according to claim 8, characterized in that the device comprises a switch (13).