Design method of long cylindrical radial magnetic field coil

Abstract

The invention provides a long cylindrical radial magnetic field coil which is composed of a plurality of pairs of saddle-shaped coils, each pair of saddle-shaped coils are symmetrically distributed on a coil framework according to a certain angle, and each saddle-shaped coil is composed of two sections of long straight wires and two sections of arc coils; wherein the directions of currents flowing through the long and straight wires are opposite, the directions of the currents of the arc sections are also opposite, and each pair of saddle-shaped coils are symmetrically distributed on the coil framework according to a certain angle. According to the technical scheme of the invention, a uniform radial magnetic field can be generated in a slender cylindrical space range, and the radial magnetic field is combined with the axial magnetic field coil to form a three-axis magnetic field coil, so that the magnetic test requirement of a long cylindrical tested piece is met.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic field reproduction, and in particular relates to a design method of a long cylindrical radial magnetic field coil. Background Art

[0002] With the development of quantum magnetic sensor technology and the increasing requirements for magnetic control in ships, vessels, satellites, etc., when the object to be measured is a long cylindrical object, only reproducing the uniform magnetic field in the axial direction can no longer meet the test requirements. New research progress requires the simultaneous reproduction of three-component uniform magnetic fields, that is, high requirements are placed on the magnetic field strength and uniformity in the horizontal radial and vertical radial directions. It is necessary to reproduce a relatively uniform radial magnetic field within the range of φ1m×(10m~25m).

[0003] At present, the commonly used three-axis magnetic field reproduction methods can be selected from Helmholtz three-axis magnetic field coils, square four-ring coils, U-shaped coils and other structures. The overall shape of the coil is approximately spherical or cube-shaped, which cannot meet the test requirements of some long cylindrical magnetic sensors or components. The more common single rectangular coil can meet the radial magnetic field reproduction within a certain length range, but its uniformity is poor, and it can only reproduce a relatively uniform magnetic field near the central axis of the winding. Therefore, when it is necessary to reproduce a uniform magnetic field within a certain cylindrical range, a single rectangular coil cannot meet the demand. Summary of the invention

[0004] In view of this, the present invention provides a design method for a long cylindrical radial magnetic field coil, wherein the magnetic field coil is composed of a plurality of pairs of saddle-shaped coils, each pair of saddle-shaped coils is symmetrically distributed on the coil frame at a certain angle, and each saddle-shaped coil is composed of two long straight wires and two circular arc coils; wherein the currents flowing through the long straight wires are in opposite directions, and the currents flowing through the circular arc segments are also in opposite directions, and each pair of saddle-shaped coils are symmetrically distributed on the coil frame at a certain angle.

[0005] In particular, the magnetic field strength B1 generated by the straight wire in the saddle coil at any point p (x, y, z) in space can be expressed by the following formula:

[0006]

[0007] Among them, θ is the angle of the starting point of the arc surface, r is the radius of the arc surface, l is the half length of the straight wire, and x, y, and z are the coordinates of point p.

[0008] In particular, the saddle coil is simplified into a rectangular coil, and the magnetic field generated by it is the sum of the magnetic fields generated by four finite length straight wires, where the magnetic fields generated by the four wires are superimposed on each other, and the magnetic field intensity generated at any point in space can be expressed by the following formula:

[0009]

[0010] In particular, the angle θ of each pair of saddle coils k Determined by the following formula:

[0011] N c =2N cp

[0012]

[0013] Among them, N cp is the number of saddle coil pairs, which is an odd number; N c represents the total number of pairs of saddle coils, θ k Indicates the starting angle of the kth pair of coil arc surfaces. The value range of k is: 1~N cp , are integers.

[0014] In particular, the number of turns N of each coil tk It is related to the value of θ and can be determined by the following formula:

[0015] N tk =|7×sin(θ k ×k)|.

[0016] Beneficial effects:

[0017] Through the technical solution of the present invention, a uniform radial magnetic field can be generated within the range of an elongated cylindrical space, and combined with an axial magnetic field coil to form a three-axis magnetic field coil, thereby meeting the magnetic testing requirements of an elongated cylindrical test piece.

[0018] Through the technical solution of the present invention, a design of multiple pairs of symmetrically distributed saddle coils is adopted, which can greatly improve the uniformity and effective working space of the reproduced magnetic field, and achieve a non-uniformity of 0.4% within a 40% working space, which is 138 times higher than the uniformity of a single pair of saddle coils.

[0019] Through the technical solution of the present invention, the logarithm, angle distribution and turn distribution of the saddle coil are reasonably selected, and the coil design can be optimized according to the specific application scenario, thereby reducing the coil size and power consumption while meeting the test requirements.

[0020] Through the technical solution of the present invention, a long cylindrical magnetic field coil suitable for various aspect ratios can be designed, which is not limited by traditional spherical or cubic coils, and expands the application scope of the magnetic field reproduction technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the basic structure of a saddle coil;

[0022] Figure 2 Schematic diagram obtained by simplifying the saddle coil into a rectangular coil;

[0023] Figure 3 Schematic diagram of the distribution of saddle-shaped coils on the coil frame. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0025] The present invention provides a design method for a long cylindrical radial magnetic field coil, wherein the coil is composed of a plurality of pairs of saddle-shaped coils, each pair of saddle-shaped coils is symmetrically distributed on a coil frame at a certain angle, and each saddle-shaped coil is composed of two long straight wires and two arc coils; wherein the currents flowing through the long straight wires are in opposite directions, and the currents in the arc segments are also in opposite directions, and each pair of saddle-shaped coils is symmetrically distributed on the coil frame at a certain angle. The long cylindrical radial magnetic field coil can generate a radial magnetic field perpendicular to the axial direction within a slender space, and when combined with an axial coil, it can simulate a three-dimensional magnetic field, that is, the size and direction of the magnetic field can be adjusted arbitrarily, to meet the magnetic testing requirements of long cylindrical test pieces.

[0026] The long cylindrical radial magnetic field coil is composed of several pairs of saddle-shaped coils, each of which is composed of two long straight wires and two arc coils. The currents flowing in the long straight wires are in opposite directions, and the currents in the arc segments are also in opposite directions. Figure 1 As shown,

[0027] Each pair of saddle coils is symmetrically distributed on the coil frame at a certain angle. Figure 3 shown.

[0028] The combination of multiple pairs of coils will increase the uniformity of the reproduced magnetic field and improve the effective use space inside the coils.

[0029] The magnetic field strength generated by the straight wire in the saddle coil at any point p (x, y, z) in space can be expressed by the following formula:

[0030]

[0031] Among them, θ is the angle of the starting point of the arc surface, r is the radius of the arc surface, l is the half length of the straight wire, and x, y, and z are the coordinates of point p.

[0032] The magnetic field strength generated by the arc wires at both ends at the center point can only consider the radial direction, that is, the x direction, because the axial magnetic field can offset the magnetic field generated by the arc coil at the other end.

[0033] Therefore, the saddle coil can be simplified into a rectangular coil, and the magnetic field it generates is the sum of the magnetic fields generated by four finite length straight wires, such as Figure 2 shown.

[0034] The magnetic fields generated by the four wires are superimposed on each other, and the magnetic field strength generated at any point in space can be expressed by the following formula:

[0035]

[0036] In order to improve the uniformity of the magnetic field generated by the saddle coil, the number of coil pairs can be increased so that each pair of coils is distributed at a certain angular interval.

[0037] In the present invention, when the value of θ satisfies the following relationship, a radial magnetic field with a non-uniformity of about 0.4% can be achieved within 40% of the working space.

[0038] N c =2N cp

[0039]

[0040] Among them, N cp is the number of saddle coil pairs, usually an odd number; θ k is the starting angle of the arc surface of the kth pair of coils.

[0041] For example:

[0042] If the radial coil is composed of N cp =7 pairs of saddle-shaped coils, the magnetic fields generated by all coils are superimposed on each other, and the magnetic field strength generated at the center point can be expressed by the following formula:

[0043]

[0044] where θ k The value of can be determined by the following formula:

[0045]

[0046] The starting angles of the arc segments of a single coil are 12°, 24°, 36°, 48°, 60°, 72°, and 84° respectively; the other coil in each pair of coils is symmetrical with the upper coil about the radial direction, that is, the angle difference is 180°.

[0047] The number of turns of each coil is related to the value of θ and can be determined by the following formula:

[0048] N tk =|7×sin(θ k ×k)|

[0049] From the above formula, it can be concluded that the number of turns of each pair of saddle coils are 1, 3, 4, 5, 6, 7, and 7 respectively.

[0050] N cpIt can be 7, 5, 3, 1, etc. The larger the value, the higher the uniformity of the radial magnetic field, but at the same time the difficulty of engineering implementation will increase. Therefore, 7, 5 or 3 is generally selected in practical applications. cp =1, it is a pair of ordinary saddle coils with average uniformity.

[0051] Through simulation calculation of the magnetic field generated by one pair of coils and seven pairs of coils of the same diameter and length, the following data are obtained:

[0052]

[0053] From the data in the table above, we can see that in the same area, the magnetic field non-uniformity of 7 pairs of coils is more than ten times higher than that of a single pair of saddle coils. Therefore, the arrangement and combination of multiple pairs of coils can greatly improve the uniformity of the reproduced magnetic field and expand the effective working space. This is of great significance in engineering applications, which can reduce the overall power consumption of the coil and reduce the size of the coil. However, at the same time, the more coil pairs there are, the greater the engineering workload and the greater the difficulty of implementation. Therefore, in actual applications, the number of coil pairs can be reasonably designed according to the test requirements.

[0054] By rotating the angle of each saddle-shaped coil designed above by 90°, a radial magnetic field can be generated at a mutually perpendicular angle. The two are combined to form a two-axis magnetic field coil. By adding multiple circular coils on the axis of the cylinder, the axial magnetic field can be reproduced, and the three form a three-axis magnetic field coil.

[0055] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0056] It is obvious to those skilled in the art that the embodiments of the present invention are not limited to the details of the above exemplary embodiments, and that the embodiments of the present invention can be implemented in other specific forms without departing from the spirit or basic features of the embodiments of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the embodiments of the present invention is limited by the attached claims rather than the above description, so it is intended to include all changes that fall within the meaning and scope of the equivalent elements of the claims in the embodiments of the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units, modules or devices stated in the system, device or terminal claims can also be implemented by the same unit, module or device through software or hardware. The words first, second, etc. are used to indicate names, and do not indicate any particular order.

[0057] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the embodiments of the present invention and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the above preferred implementation modes, those skilled in the art should understand that the technical solutions of the embodiments of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for a long cylindrical radial magnetic field coil, characterized in that: The magnetic field coil is composed of a plurality of pairs of saddle-shaped coils, each pair of saddle-shaped coils is symmetrically distributed on the coil frame at a certain angle, and each saddle-shaped coil is composed of two long straight wires and two arc coils; wherein the currents flowing through the long straight wires are in opposite directions, and the currents flowing through the arc segments are also in opposite directions, and each pair of saddle-shaped coils is symmetrically distributed on the coil frame at a certain angle.

2. The design method of the long cylindrical radial magnetic field coil according to claim 1, characterized in that: The magnetic field strength B1 generated by the straight wire in the saddle coil at any point p (x, y, z) in space can be expressed by the following formula: Among them, θ is the angle of the starting point of the arc surface, r is the radius of the arc surface, l is the half length of the straight wire, and x, y, and z are the coordinates of point p.

3. The design method of the long cylindrical radial magnetic field coil according to claim 2, characterized in that: The saddle coil is simplified into a rectangular coil, and the magnetic field generated by it is the sum of the magnetic fields generated by four finite length straight wires, where the magnetic fields generated by the four wires are superimposed on each other. The magnetic field intensity generated at any point in space can be expressed by the following formula:

4. The design method of the long cylindrical radial magnetic field coil according to claim 3, characterized in that: The angle θ of each pair of saddle coils k Determined by the following formula: <h2 style=";text-align:left;direction:ltr">N<h2 style=";text-align:left;direction:ltr"> c <h2 style=";text-align:left;direction:ltr"> <2N<h2 style=";text-align:left;direction:ltr"> cp Among them, N cp is the number of saddle coil pairs, which is an odd number; N c represents the total number of pairs of saddle coils, θ k Indicates the starting angle of the kth pair of coil arc surfaces. The value range of k is: 1~N cp , are integers.

5. The design method of the long cylindrical radial magnetic field coil according to claim 4, characterized in that: The number of turns of each coil is N tk It is related to the value of θ and can be determined by the following formula: N tk =|7×sin(θ k ×k)|。

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