SU828220A1 - Pulsed high-voltage lead-in - Google Patents

Description

The invention relates to electrical engineering, namely to pulsed high-voltage bushings, and can be used in the design of accelerator tubes of high-current pulsed accelerators and high-voltage bushings for pulsed power supply of electron guns of gas lasers with non-self-sustained discharge.

High voltage bushings are known in which an increase in the electric strength ω for fast processes is achieved by the method of sectioning the structure with screening of the insulator wall by electrodes of a special shape [1].

The device of this input consists of a series of 15 dielectric rings interconnected by aluminum rings that protrude slightly beyond the edges of the dielectric. A semiconducting polyurethane cylinder is inserted inside the insulator. The conductivity of this cylinder ensures uniform distribution of voltage across the insulator sections in static mode. However, such devices are difficult to manufacture. 25

Pulse high-voltage bushings in vacuum volume are also known, the insulators of which are implemented with a resistive voltage distribution along the length [2]. Most simply, such a distribution can be obtained by using a hollow insulator filled with electrolyte. However, this solution does not eliminate the danger of breakdown along the vacuum surface of the insulator caused by processes whose characteristic times are less than the discharge time constant of stray capacitances, determined by the thickness of the insulator wall, through the electrolyte. For example, a breakdown caused by a fall on the wall of a beam of charged particles.

The aim of the invention is to increase the electrical strength along the outer surface of the input.

This goal is achieved by the fact that in the known high-voltage input into the vacuum volume containing the housing of insulating material, made in the form of two coaxially arranged cylinders, the cavity between which is filled with electrolyte, electrodes vacuum-tightly located at the ends of the housing, and a current-carrying element passing through the inner cylinder, on the outer surface of the outer cylinder is wound a wire or tape of conductive material, the ends of which are connected to the electrodes.

In FIG. 1 shows a pulse high voltage input; in FIG. 2 — high voltage input option.

• 3

The pulsed high-voltage input consists of high-voltage 1 and grounded 2 electrodes, between which the vacuum is tightly fixed to the housing, consisting of the outer 3 and inner 4 cylinders, the space between which is filled with electrolyte 5. On the outer surface of the cylinder 3 there is a metal wire or tape forming a winding 6. The inner surface of the cylinder 4 is in an insulating medium that provides electric strength along the inner surface of the cylinder 4 (oil, compressed gas). The connection of the high-voltage electrode 1 with a source of high-voltage pulse voltage U _{o is} carried out by a conductor 7 located in an insulating medium inside the cylinder 4.

The device operates as follows.

When applying a voltage pulse to the electrode 1 on the inner surface of the cylinder 3 due to the presence of electrolyte 5, a uniform potential distribution is established. The initial potential distribution on the outer surface of the cylinder 3 is determined by the ratio of the partial capacitances: the inter-turn capacity of the winding, the capacitance between the coil of the winding and the ground, and the capacitance between the coil of the winding and the electrolyte.

It can be shown that the initial potential distribution over the outer surface of the cylinder is determined by the following relation:

where U (x) is the potential of the insulator wall at a point with the coordinate x, measured from the high-voltage electrode;

I is the length of the insulator;

a = (H ± LH_) T, β ₌ - £ 1--.

\ k J s] -G s-.

Ci is the capacitance between the coil of the winding and the electrolyte;

.¾ is the capacitance between the coil of the winding and the ground;

k is the capacitance between two adjacent turns of the winding.

From the above relation (1) it can be seen that if the capacitance between the coil and the electrolyte is significantly larger than the capacitance between the coil and ground (C]> c ₂ ), then β ^ = Η and the potential distribution turns out to be uniform ~] - ± (2)

E I

In practice, the condition Ci »c ₂ is fulfilled and it can be concluded that this input device4 provides an almost uniform initial distribution of potential along the insulator.

The presence of a metal winding protects the surface of the insulator from accidental accumulation of surface charges caused, for example, by the acceleration of particles on the insulator.

The influence of the inductive resistance of the winding on the load current is small if the duration of the high voltage pulse t _{n is} significantly less than the time constant x = LjR, where L is the magnitude of the inductance of the winding;

R is the resistance determined by the parallel inclusion of the load resistance and the resistance of the electrolyte.

For example, a high-voltage input with cylinder 3 with a length of 510 mm and a diameter of 480 mm with a winding of 160 turns has an inductance connected in parallel with a load of 100 Ohms, a value of 12 mG. In this case, m = 120 μs and the decrease in the area of the voltage pulse with a duration of ί _η = 5 μs does not exceed 4%. With c ₂ = 0.1 Ci and Ci = k, the nonuniformity of the initial potential distribution over the surface of the insulator does not exceed 0.6%.

Another variant of the high voltage input into the vacuum volume is as follows.

The core of the coaxial cable 7 is connected to the high-voltage electrode 1, and its braid to the grounded electrode 2. Here, the core of the cable with its insulation immersed in the electrolyte 5 serves as the internal insulator 4.

Claims (2)

The pulse high-voltage input consists of a high-voltage 1 and a grounded 2 electrodes, between which a vacuum is tightly fixed to a case consisting of an outer 3 and an inner 4 cylinder, the space between which is filled with electrolyte 5. On the outer surface of the cylinder 3 there is a metal wire or tape forming a winding 6 The inner surface of cylinder 4 is in an insulating medium that provides electrical strength along the inner surface of cylinder 4 (oil, compressed gas). The high-voltage electrode 1 is connected to the high-voltage impulse voltage source t / o by conductor 7 located in an insulating medium inside the cylinder 4. The device operates as follows. During iodation of a voltage pulse to electrode 1, a uniform distribution of notional is established on the inner surface of cylinder 3 due to the presence of electrolyte 5. The initial potential distribution over the external surface of the cylinder 3 is determined by the ratio of partial capacities: between the winding capacitance of the winding, the capacitance between the coil of the winding and the ground, and the capacitance between the coil of the winding and the electrolyte. It can be shown that the tactile distribution of potential on the outer surface of the cylinder is determined by the following relation: | (lp + Ml-f) l, (l) С / о where / (l :) is the insulator wall potential at the x-coordinate, counted from a high-voltage electrode; / is the length of the isolator; 1 k ICi + Сз Ci is the capacitance between the turn of the winding and the electrolyte; Cz is the capacitance between the winding coil and ground; k is the capacitance between two adjacent turns of the winding. It’s clear from relation (1) that if the capacitance between the coil and electrolyte is significantly larger than the capacitance between the coil and the ground (), then the potential distribution is even, 1 In practice, the condition is fulfilled and it can be concluded that this input device provides an almost uniform initial potential distribution along the insulator. The presence of a metal winding protects the surface of the insulator from accidental accumulation of surface charges caused, for example, by the introduction of accelerated particles onto the insulator. The influence of the inductive resistance of the winding on the load current is small if the duration of the high voltage pulse tn is substantially less than the time constant, where L is the magnitude of the inductance of the winding; R is coherently determined by the parallel connection of the load resistance and the resistance of the electrolyte. For example, a high-voltage input with a cylinder 3 with a length of 510 mm and a diameter of 480 mm with a winding of 160 turns possesses an inductance connected in parallel with a load of 100 Ohm, 12 mg in value. In this case, the ISS and the decrease in the area of the voltage pulse with a duration of μs does not exceed 4%. With, 1 Ci and non-uniformity, the initial potential distribution over the insulator surface does not exceed 0.6%. Another option for high-voltage input to the vacuum volume is made as follows. The core of the coaxial cable 7 is connected to the high-voltage electrode 1, and its braid is connected to the grounded electrode 2. The internal insulator 4 is the cable core with its own insulation immersed in the electrolyte 5. The invention impulse high-voltage input into the vacuum volume, comprising material, made in the form of two coaxially arranged cylinders, the cavity between which is filled with electrolyte, electrodes, vacuum-tightly located at the ends of the body, the tokedo passing through the morning cylinder conductive element, wherein the. that, in order to increase the electrical strength, a wire or strip of conductive material is wound on the outer surface of the outer cylinder, the ends of which are connected to the electrodes. Sources of information taken into account in the examination 1.NATENT USA L3216439, cl. 174-31, 1964. 2. Authors sviletelstvo USSR № 465143, cl. H 05K 5/00, 1973.