RU2521867C1 - Solenoid coil - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: solenoid coil comprises an excitation winding and an external magnet core consisting of a cylindrical shell and two end flanges, which inner surfaces are magnet poles. The excitation coil consists of the main winding with a rectangular cross-section and two compensating windings of a V-shaped cross-section, which are wound around peripheral parts of the main winding with the rectangular cross-section. The main winding with the rectangular cross-section is wound on top of a cylindrical water-cooling jacket of a non-magnet material. The space between the main winding, two compensating windings of the V-shaped cross-section and the cylindrical shell of the external magnet core forms a gas-cooling jacket. The end flanges have a shape of cones protruding outside, where coaxial cone cutouts with peaks at pole surfaces are made. The angles at the base of the cones ensure equal density of a magnetic flux along the whole length of the magnet lines in the external magnet core.

EFFECT: improvement of uniformity and homogeneity of a magnetic field and power.

12 dwg, 3 tbl

Description

The present invention relates to the technique of electromagnets, creating single-row magnetic fields of medium and high levels of magnitude with an axial extent many times greater than the radial, with a high uniformity within the entire space. Such devices are needed for modern experimental physics and for creating a working space region with autoresonant acceleration or generation.

The aim of the invention is to provide a device with a uniform magnetic field in a cylindrical volume; with a diameter of about 100 mm and a length of about 300-500 mm, a magnetic field level of up to 10 kilogauss, efficient conversion of the energy of the supplying electric current into a magnetic field, and continuous operation.

The essence of the invention consists in the application of compensating windings over the peripheral parts of the main winding of rectangular cross-section, placing the entire winding in an external armored magnetic circuit with profiled end flanges. To remove heat from the windings, water and gas cooling shirts were used.

An analogue of the invention is a microtron electromagnet, see S.P. Kapitsa, V.N. Melekhin ′ ′ Mikrotron ′ ′ Science. M .: 1969, FIG. 1. Structurally, the microtron magnet consists of an armored housing 1, with two opposite poles 2, with field windings 3. Axial clearance 4 between the poles 2 is determined by the diameter of the accelerating resonator 5. For a typical microtron, axial clearance 4 is 120 mm . The diameter of the poles 2 is 700-2000 mm. The magnitude of the magnetic field is 1000 g with a uniformity of 0.01-0.5%. The windings are made of a small copper busbar and do not use special cooling.

The disadvantage of the analogue is that it creates a short section of the magnetic field compared to its diameter and a simple increase in the axial size of this analogue will not ensure the creation of an extended uniform magnetic field. A method of constructing a magnetic circuit with thick poles deserves attention.

The first prototype of the invention is the solenoid S.P. Kapitsa, see Collection “′ High Power Electronics” ′. USSR Academy of Sciences M .: 1963, pp. 103-118, FIG. 2. An essential feature of this device is an increase in the magnetomotive force of the winding at the periphery. Structurally, the winding consisted of tape rolls 1 composed along a common axis of symmetry. The cross section of the tape in the central rolls was 25 × 0.4 mm ² , .a peripheral 2.5 × 0.2 mm ² . The inner diameter of the winding was 170 mm, the outer 332 mm, the length of the winding was 727 mm. The nominal mode of the magnetic field is 4.5 kgf. The uniformity of the magnetic field was no worse than 0.06%, FIG. 3. The radial distribution of the magnetic field has not been investigated.

The main disadvantage of the first prototype in the small relative length of a uniform magnetic field 370/727 = 0.51.

The second drawback of the first prototype is the creation of a strong magnetic field in the space surrounding the solenoid, which complicates and even makes impossible the operation of many devices.

The third drawback is associated with the second, and it consists in the large power consumption for food, winding 36 kW.

The second prototype of the invention is a device, see Kapitsa P.L., Filimonov S.I. “Solenoid, creating a magnetic field of up to 30 kilo-ersted in a volume of 5 liters, and consuming 500 kilowatts” ”, High-power electronics No. 6, Moscow: Nauka, 1969, p.147-160, Fig. 4.

The essence of this device is that the winding was made of two groups of roll cassettes 1, separated by a gap of 32 mm and placed in the casing of the cooling jacket 2, through which distilled water was passed.

The second difference of this prototype was the use of an external jugular type 3 magnetic circuit from a steel plate with a cross section of 540 × 90 mm ² . The inner diameter of the winding is 160 mm, the outer is 360 mm, the length of the solenoid along the winding is 408 mm, and along the magnetic circuit is 586 mm. At the poles of the magnetic circuit there were through axial holes equal to the inner diameter of the solenoid winding.

With a power supply of the winding of 500 kilowatts, the magnetic field reached 30 kiloersted. The axial distribution of the magnetic field in this mode was with a uniformity of 5.5%, FIG. 5.

The disadvantage of the second prototype is the low level of uniformity of the magnetic field, which is due to the use of spaced, divided by the gap of the two groups of cassettes.

The second disadvantage of this device is the low quality of the magnetic shielding of the solenoid, because the winding was open on both sides. And at the ends, the solenoid was also opened with large holes with a diameter of 140 mm. All this reduced the quality of shielding.

The third prototype of the invention is a device, see cand. dis. Ishkov. A.P. ′ ′ Experimental study of autoresonant electron acceleration ", TPI, Tomsk, 1969, p. 50-52, Fig. 6.

The third prototype consists of a modified Helmholtz coil system 1. The modification consisted in the use of a third compensating coil 2, which was placed between the main coils 1. With an internal diameter of 190 mm, an external 360 mm: and a total length of 260 mm, a working magnetic field of 1000 gf was obtained on the site 160 mm long along the axis of the magnetic system.

The second significant difference of this prototype was the use of an external magnetic circuit in the form of two end disks 3 and eight side plates 4. The entire magnetic circuit was made of mild steel with a thickness of 30 mm.

The third feature of this prototype was the use of disks with running water 5, which were axially pressed against coils 1 and 2. The inner disks were brass, and Archimedes spirals were machined in the outer disks 5.

In general, the prototype in the experiment showed acceptable results: the excitation current of the winding decreased 2.6 times, the duration of the solenoid increased from 1-2 minutes to 5-6 minutes, the uniformity of the magnetic field improved from 3% to 1-2%, FIG. 8.

The structure of the magnetic field in the diametrical plane of the solenoid is shown in Fig. 7. An analysis of lines of equal level of the magnetic will shows that each coil creates its own local region of the magnetic field with obvious “hollows”, where the level of the magnetic field is much lower than the “hillocks” adjacent to the coils.

The main disadvantage of the third prototype is the irrationality of the magnetic circuit: the side part had gaps between the side plates 4, the end plates 3 had large holes with a diameter of 190 mm.

The disadvantage of the winding was that it was made up of three spaced coils that created their local maxima - ″ hillocks ″, and between them there were ″ hollows ″. This reduced the uniformity of the magnetic field.

The cooling system was inadequate.

The noted disadvantages were eliminated in the fourth prototype, see patent RU2364000 ″ Ishkova homogeneous solenoid ″, FIG. 9.

The fourth prototype consists of a winding of rectangular cross-section 1 and an external armored magnetic circuit 2, magnetic field lines 3 connect the poles 4. The solenoid of such a device has been tested experimentally and really provides a given uniformity of the field in it.

Its drawback is the formulated feature of the magnetic circuit: its thickness should be equal to the internal radius of the field coil. Such a solenoid is easy to manufacture if it is small in size. And if the dimensions increase, then the solenoid becomes unrealizable.

It is required to improve both the winding and the magnetic circuit.

By way of example, the invention is shown in FIG. 10. It consists of a main winding of rectangular cross section 1, which extends the entire length of the solenoid and two compensating windings of triangular cross section 2, which are wound over the peripheral parts of the main winding of rectangular cross section 1. The device is equipped with an external armored magnetic circuit 3, which consists of a cylindrical shell 4 and two end flanges 5. The thickness of the cylindrical shell 4 is the same in its entire surface and is selected according to the mode of magnetic not saturation.

End flanges 5 have the shape of truncated cones, the inner surfaces of which are implicit poles 6. The size h at r = r ₁ is selected according to the criterion for the magnetic flux density being equal in all sections of the armored magnetic circuit 3: at implicit poles 6, inside end flanges 5 and inside cylindrical shell 4.

πn ² = 2πnh = 2πr ₃ · Δ,

where h is the height of the end flanges 5 when r = r ₁ ,

Δ is the thickness of the cylindrical shell 4,

r ₁ - inner radius of the main winding of rectangular cross section 1,

r ₃ is the outer radius of the compensating winding of a triangular section 2.

$$\Delta =\frac{n}{6}$$

при $$r_3=3r_1.$$

Hence: $$h=\frac{r_{\mathrm{one}}}{2},$$

$$\Delta =\frac{n}{6}$$

at $${\mathrm{<figure-callout\; id="3"\; label="r"\; filenames="00000015.png,00000017.png"\; state="\{\{state\}\}">r</figure-callout>}}_3=3r_{\mathrm{one}}.$$

In the end flanges 5, cutouts of a conical shape 7 with vertices at the implicit poles 6 are coaxially made outside. They do not violate the structure of the magnetic field lines B _z 12 between the implicit poles 6 and are intended for communication with the internal space of the solenoid.

The main winding of rectangular cross section 1 is wound over a water cooling jacket 8, which is equipped with nozzles 9 for supplying cooling water and draining it into the cooling system in a known manner.

The space formed by the main winding of rectangular cross-section 1 with compensating windings of triangular cross-section 2 and cylindrical shell 4 creates a gas cooling jacket 10, which is equipped with a pipe 11 through which cooling gas circulates in a known manner. As a gas refrigerant can be used: hydrogen, helium or compressed air. Their specific heat is given in table. one

Table 1 cool. agent temperature mode specific heat water 0-100 ° C 1 cal / gr hydrogen 0-200 ° C 3.41 helium 0-600 ° C 1.24 air 0-400 ° C 0.24

Of these, hydrogen is physically most effective, but compressed air is technologically simpler and more convenient.

The device operates as follows.

An electric current flowing in the main winding of rectangular cross-section 1 creates a magnetic field B _z (xz) inside it. According to studies of the first prototype, FIG. 3, its axial distribution has a fairly flat maximum in the central part and a progressive decline in the periphery. To equalize the value of B _z (xz) along the entire length of the solenoid, two compensating windings of triangular section 2 are used. Their profile is consistent with the axial decrease in the magnetic field created by the main winding of rectangular section 1. With appropriate selection of the electric current in compensating windings of triangular section 2, a magnetic the field B _z (xz) of one level with sufficient accuracy.

The heat released in the main winding of rectangular cross-section 1 and in the compensating windings of triangular cross-section 2 is removed by running water flowing through the water cooling jacket 8 and the flow of cooling gas through the gas cooling jacket 10 by known methods.

The magnetic field B _z (xz) created by the main winding of rectangular cross-section 1 and compensating windings of triangular cross-section 2 according to studies of prototype 3, FIG. 7, has a radial heterogeneity: with the axis of symmetry, the magnetic field B _z (xz) has a minimum, with a radial distance from the axis of symmetry to the inner surface of the main winding of rectangular cross section 1, the magnitude of the magnetic field B _z (xz) increases parabolic. The use in the magnetic circuit 3 of two end flanges 5 in the form of truncated cones redistributes the lines of magnetic induction B _z (xz) so that the radial distribution of the magnetic field B _z (xz) becomes uniform, independent of the radial coordinate x.

The axial thickening of the end flanges 5 in the axial region of the solenoid significantly reduces the magnetic resistance for the magnetic field lines B _z (xz) 12 than in the peripheral part remote from the axis of symmetry. This contributes to the radial alignment of the magnetic field inside the solenoid.

The final refinement of the magnetic field uniformity B _z (xz) can be achieved by profiling the implicit poles 6 of the end flanges 5 according to the technique used for microtrons, i.e. for analogue.

Table 2 Prototype r ₁ / r ₂ ΔZ / Z heterogeneity h mm Δ, mm one 85/166 = 0951 370/727 = 0.51 0.06% 42 22 2 80/180 = 0.44 200/406 = 0.49 5.5% 40 eighteen 3 85/170 = 0.5 200/240 = 0.83 2% 42 (30) 21 (0) four 15/35 = 0.43 82/82 = 1 5% 9 9

Table 2 presents the main parameters of the prototypes. In the first column, the numbers of the prototypes in order of their use in the text. The second column shows the ratio of the radii of their windings: internal to external. In the third column, the ratio of the length of the section with a uniform magnetic field to the total length of the winding. The fourth column shows the achieved level of uniformity of the magnetic field.

In the last two columns, the calculated parameters of the external magnetic cores obtained by the method of the invention, page 4 are carried out.

For the first prototype, the use of a cylindrical shell with a thickness Δ = 22 mm and end flanges with a design parameter h = 42 mm would reduce the power consumption from 36 kW to 6-8 kW. In this case, the space surrounding the solenoid would be without a strong external magnetic field.

The second prototype with a cylindrical shell Δ = 18 mm and closed, without holes, flanges with the parameter h = 40 mm would provide better uniformity of the magnetic field.

In the third prototype, a continuous cylindrical shell 21 mm thick instead of a periodic of eight plates 30 mm thick and end flanges with the parameter h = 42 mm instead of 30 mm would provide better uniformity with closed flanges and better protection of the surrounding space from radiation during operation accelerator.

The last line shows the parameters of the fourth prototype.

The overall result of the information contained in Table 2 is that the external magnetic circuit of the present invention more effectively increases the uniformity of the magnetic field of the original solenoid and protects the surrounding space from the external magnetic field of the solenoid.

Of particular interest is the theoretical calculation of the structure of the magnetic field created by a circular current.

In FIG. 11 shows a circular circuit with current i. The magnetic field B _z at an arbitrary point x on the x axis, at a distance x from the origin according to the Laplace’s law will be determined by the sum of all elementary fields dB _z created by all elements of the circular current i according to the Laplace’s formula

$$d{B}_z=\frac{idl}{{\delta }^2}=i\frac{rdy}{{\delta }^2}.\text{(one)}$$

the length of the segment δ is determined by the cosine theorem

$${\mathrm{<figure-callout\; id="2"\; label="\delta "\; filenames="00000015.png,00000017.png"\; state="\{\{state\}\}">\delta </figure-callout>}}^2=x^2+r^2-2rx\cos y.\text{(2)}$$

As a result, the magnetic field at point x, which is spaced from the center of circular current i at a distance x, will be numerically equal to the integral

$${\text{B}}_{\text{z}}\text{(x)}=i{r}_0{\displaystyle \underset{T}{\overset{2h}{\int }}\frac{dy}{x^2+r^2-2rx\cos y}}.\text{(3)}$$

and the point x _^1, spaced from a circular current in the region Z plane magnetic field B _z (xz) according to FIG. 12 is determined by the integral.

$$B^{\text{'}\text{'}}(\dot{x}z)=ir{\displaystyle \underset{0}{\overset{2h}{\int }}\frac{dy}{x^2+{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="00000015.png,00000017.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+Z^2-2rx\cos y}.}\text{(four)}$$

Its projection onto the Z axis is determined by cosα, which is numerically equal to

$$\cos \alpha =\frac{\delta }{{\delta }^{\text{'}\text{'}}}=\frac{\sqrt{x^2+r^2-2rx\cos y}}{\sqrt{x^2+{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="00000015.png,00000017.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+Z^2-2rx\cos y}}.\text{(5)}$$

The result is a formula for determining the spatial distribution of the magnetic field created by the circular current i

$$B_z(x,z)=ir{\displaystyle \underset{0}{\overset{2h}{\int }}\frac{\sqrt{x^2+r^2-2rx\cos y}}{\sqrt{{\left(x^2+{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="00000015.png,00000017.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+Z^2-2rx\cos y\right)}^{\raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}}}dy}\text{(6)}$$

If r = 1 and the x, Z coordinates are measured in its shares, then the formula will be simplified

$$B_z(x,z)=2i{\displaystyle \underset{0}{\overset{\pi }{\int }}\frac{\sqrt{\mathrm{one}+x^2-2x\cos y}}{{\left(\mathrm{one}+x^2+Z^2-2x\cos y\right)}^{\raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}}dy}\text{(7)}$$

Table 3 shows the magnetic field created by the circular current i = 1.

Table 3

x Z 0 0.250 0.5 1,0 1,5 0 0.913 1,0 0.716 0.353 0.171 0.2 0.941 1,04 0.720 0.349 0.169 0.4 1,032 1.19 0.738 0.336 0.162 0.6 1,156 1,562 0.743 0.311 0.153 0.8 1,406 1,406 0.697 0.281 0.143

The field at the center of the circular current is taken as 1.0. The magnetic field B _z (xz) along the Z axis decreases monotonically, and along the x axis in the plane of circular current, the magnetic field increases parabolic. This is the so-called trace distribution.

In a plane separated by 0.25 radius, the magnetic field also grows radially, and at a distance of 0.5 radius it has a maximum at x = 0.6 and then goes down. With further distance from the plane of the circular current, the magnetic field only decreases in radius.

Using the obtained formula 7, you can use a computer to calculate the internal structure of the magnetic field of any solenoid

The next step is an experimental verification of formula 7.

Claims (1)

A solenoid consisting of an excitation winding and an external magnetic circuit consisting of a cylindrical shell and two end flanges, the inner surfaces of which are magnetic poles, characterized in that the excitation winding consists of a main winding of a rectangular section and two compensating windings of triangular sections, which are wound over the peripheral parts the main winding of a rectangular section, the main winding of a rectangular section is wound on a cylindrical water-cooling shirt, which is made on a non-magnetic material, the space between the main winding of rectangular cross section, the two triangular cross sections of the compensating coils and the cylindrical outer shell magnetic circuit is jacketed cooling gas, front flanges are in the form of cones that protrude outwardly and are made of coaxial conical recesses with vertices on the pole surfaces; the angles at the bases of the cones provide uniform magnetic flux density along the entire length of the magnetic lines in the external magnetic circuit.

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