DE2553735A1 - Capacitor with pressure gas bearing for electrodes - uses gas bearing to define mutual electrodes position and guide elements mounting - Google Patents

Abstract

The variable capacitor has metal electrodes whose mutual position, as well as the guide and adjustment elements, is determined by a pressure gas bearing. Each of the bearing is supplied from outside with pressurised gas via bores or slots leading into the respective bearing gap. The bearing body preferably consists of a porous, permeable material, permitting pressurised gas passage to the bearing gap. The bearing body may be alternately partly of porous and partly of non-permeable material. The electrodes spacing and thus the capacitance value can be changed by gas pressure variations. If nozzles are used for gas supply the variability can be obtained by changing their numbers.

Description

Execution of capacitors by means of pressure-fed storage of the

El ek Lroden und Verctellelemente The invention relates to the application Pressure-fed bearings in air condensers instead of bearings with solid insulating materials.

This is of particular interest for capacitors that are used to achieve large capacitance values () 1000 pF) small electrode distances with negligible at the same time should have small loss factors tan 6.

Conventional types of air condensers use mutual Isolation of the two electrodes solid insulating materials such. B.

Glass, quartz, Teflon etc .. By ohmic dissipation and dielectric Losses of such insulating materials increase the loss factor at low frequencies of a capacitor in a way that cannot be precisely determined, since the loss factor is more fixed Insulating materials depend on frequency, temperature and humidity and are not resistant to aging is.

The total loss factor of the capacitor goes through the solid insulating materials, which can also only be determined uncertainly Lets. References: A. V. Astin, Nature of Energy Losses in Air Capacitors at Low Frequences, Part of Journal of Research of the NBS, Vol. 22, June 19393. These Disadvantages concern both fixed capacitors and capacitors with variable Capacity.

Adjustable capacitance capacitors are commonly called Plate capacitors run, the capacitance changes either by variation the electrically effective electrode surfaces or by changing the distance between the plates can be achieved.

Literature: B. Hague, T. R. Foord, Alternating Current Bridge Methods, Pitman Publishing, London, 6th Edition 1971, pp. 194-209) For capacitors with variable Plate spacing adds to the disadvantages mentioned above, that with handy Plate dimensions, capacitance changes are limited to ~ 1000 pF. aside from that plate distances are less than 100 µm to achieve capacitance values> 1000 pF, how they z. B. required for measurement methods in the frequency range between 1000 Hz and 1 MHz due to the possible risk of short circuits due to insufficient parallel guidance of the Electrodes have not been realized. Because of the imprecise parallel execution purely mechanical means are also effective with capacitors with changeable Electrode surfaces (e.g. cylinder capacitors) Electrode spacing (100 / µm not feasible.

These disadvantages are due to the inventive arrangement of a Capacitor is significantly reduced. With her, the electrode distance can be opposite significantly reduce the size of the previously known arrangements, thereby increasing the capacity accordingly is increased.

The invention is characterized in that gas bearings for holding, Guide and adjustment of capacitor electrodes can be used.

This is particularly beneficial for capacitors where there is to a negligible loss factor tan 5 with large capacitance values at the same time and as large an adjustment range as possible with manageable panel dimensions is important.

According to the invention, this object is achieved by a capacitor arrangement solved, in which the electrode surfaces form the bearing parts of a gas bearing. This The system exists in the case of a plate capacitor with variable plate spacing 1. from an electrode in which there are throttle organs, 2. from a plate as a counter electrode with a mechanical structure for centering and electrical Connection according to Figures 1 and 3 of a gas supply device.

As throttling organs through which, for reasons of stability, the under pressure standing gas is pressed into the electrode gap, are suitable directly into an electrode or nozzles drilled into the adjustment elements. Literature: R. Unterberger, Calculation and application of the pressure-fed air bearing, magazine for practical metalworking 62 (1968), no. 4 1, or a porous, permeable material [literature: H. J. Sneck, A Survey of Gas-Lubricated Porous Bearings, Trans ASME, Ser. F, Vol. 90, No. 41. The following advantages result from this storage: 1. That for support and guidance of the electrodes used gas also serves as largely loss-free it dielectric. This eliminates the need to use a solid dielectric, which is the case with conventional design for isolating mechanical components from the electrodes necessary is. This results in a very small loss factor tan 6, which is also on ohmic losses in the leads and electrodes and in the dielectric Layers on the electrode surfaces is due. Thus it becomes an absolute determination of the loss factor possible.

2. Due to the inherent stability of the air cushion, there is good parallel guidance of the electrode plates and constancy of the plate spacing ensures that too prevents a short circuit with the smallest plate spacing (10 μm).

3. The variation of the plate spacing and thus of the capacitance value is in a simple way by changing the effective number of nozzles in combination possible with a change in the gas supply pressure.

4. The change in the electrically active surface and thus the Capacitance value due to relative movement of the electrodes to each other is due to the use the gas bearing extremely low-friction and jolt-free.

An embodiment of a plate capacitor with variable Plate spacing is shown in Figure 1 and is described in more detail below: Purified and dried nitrogen flows through a fine pressure reducer 11 the connection 7 and a number of nozzles 8 in the electrode 1 in the electrode gap and in the gap around the centering piece 4. The electrode 2 is formed by the Gas film lifted from the electrode 1. The gap height (plate spacing) is included depending on the set gas pressure, the number of effective nozzles and the Weight of the electrode 2. The number of nozzles can be set externally via valves. The electrode 2 is through the inner conductor 6 of the coaxial connector and a spring 9 electrically connected and at the same time centered radially via the centering piece 4. Due to the axial fixation of the centering piece and the use of the spring a constant contact pressure of the center conductor in the coaxial connector even if the gap changes guaranteed between the two electrodes.

As an example of a capacitor with variable effective electrode areas the arrangement of a cylinder capacitor with a gas bearing is sketched in FIG. This version has the property that even with a very small distance (~ 10 / um) of the electrodes, the inner electrode 2 is centered with respect to the outer electrode 1 and is mounted without friction. A micrometer screw is used as the adjustment element 12 with an air supply 7, at the front end of which is a disc as a throttle element 13 is attached from porous, permeable material. The gas store so formed insulates the inner electrode from the adjustment element.

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Claims (1)

P a t e n a n s p rü c h e Claim 1 arrangement of a capacitor with metal electrodes, characterized in that the mutual position of the electrodes, Guide and adjustment elements is set by means of gas bearings. Claim arrangement of a storage of electrodes and adjustment elements of a condensate according to claim 1, characterized in that pressure-fed Bearings are used where there are openings (bores, slots) under gas External pressure is pressed into the respective bearing gap. Claim 3 arrangement of a pressure-fed storage of a capacitor according to claim 1, characterized in that a bearing body made of porous, permeable There is material through which the gas enters the respective bearing gap under pressure from the outside is pressed. Claim 4 arrangement of a pressure-fed storage of a capacitor according to claim 1 and 3, characterized in that a bearing body partially consists of porous, permeable and partially made of non-porous material. Claim 5 arrangement of pressure-fed storage of a capacitor according to claim 1, 2, 3 and 4, characterized in that by changing the gas pressure the electrode spacing and thus the capacitance value of the capacitor is changed. Claim 6 arrangement of a pressure-fed storage of a capacitor according to claim 1 and 2, characterized in that by changing the effective Dtisenzahl the electrode gap and thus the capacitance value of the capacitor changed will. Claim 7 arrangement according to claim 1, 2, 5 and 6, characterized in that that by changing the nozzle diameter, the electrode spacing and thus the capacitance value of the capacitor is changed. Claim 8 arrangement of a pressure-fed storage of a capacitor according to claim 1, 3 and 4, characterized in that for changing the electrode spacing as throttle elements porous, flowable materials with different spec. Permeability be used.