Pipe fitting machining method and device based on discrete magnetic collector

Abstract

The invention belongs to the field of metal forming and manufacturing, and particularly relates to a pipe fitting machining method and device based on a discrete magnetic collector, the discrete magnetic collector is arranged between a driving coil and a pipe fitting to be bulged, the discrete magnetic collector comprises a first magnetic collector ring and a second magnetic collector ring, and the cross section of the first magnetic collector ring and the cross section of the second magnetic collector ring are both trapezoidal. And the discrete magnetic collector and the outer surface of the driving coil are fixedly connected through a reinforcing material and are packaged into a whole. The first magnetic collector ring is arranged at the end of the pipe fitting forming area, the sectional area of the first magnetic collector ring is larger than that of the second magnetic collector ring, radial electromagnetic force borne by the end of the pipe fitting forming area is increased, the uniformity of the forming area is better after the pipe fitting is formed, and the pipe fitting forming effect can be improved. According to the invention, the structural strength of the coil is enhanced by using the discrete magnetic collector, so that the electromagnetic field intensity generated by the induced eddy current of the pipe fitting in the coil is reduced, and the electromagnetic force borne by the coil is fundamentally weakened while the forming effect is not influenced, so that the coil can be better protected.

Description

Technical Field

[0001] The invention belongs to the field of metal forming and manufacturing, and in particular relates to a pipe processing method and device based on a discrete magnetic concentrator. Background Art

[0002] As a high-rate pulse forming technology, electromagnetic forming technology can significantly improve the forming limit and surface quality of metal materials. In recent years, it has been widely used in the field of metal workpiece forming and manufacturing. However, since the current in the driving coil that provides the electromagnetic field for the metal workpiece forming process is opposite to the direction of the induced current in the metal workpiece, the driving coil is subject to the electromagnetic force under the electromagnetic field of the induced current in the metal workpiece and the electromagnetic field generated by the driving coil itself during the workpiece forming process, and is prone to expansion and failure of the driving coil. Therefore, enhancing the structural strength of the driving coil and protecting the driving coil are of great significance to improving the service life of the driving coil. The paper "1.5 T magnetic induction intensity water-cooled solenoid coil structure design and simulation research" published by Ye Yi, Long Quanhong and others in the journal "High Power Laser and Particle Beam" concluded through simulation research that the temperature rise of the driving coil will reduce the structural strength of the coil. The paper "Analysis of coil temperature rise in electromagnetic forming with coupledcooling method" published by Qiu Li, Deng Kui and others in the journal "International Journal of Applied Electromagnetics and Mechanics" proposed to use coupled cooling method to reduce the temperature rise of the driving coil, so as to reduce the temperature rise of the driving coil. It can be seen that the structural strength of the drive coil mainly depends on the winding process and the physical properties of the reinforcement material. However, during the operation of the drive coil, the excessive electromagnetic force and excessive temperature rise applied to the drive coil during the workpiece forming process will reduce the structural strength of the coil and greatly reduce its service life. Summary of the invention

[0003] The technical problem of the present invention is that the driving coil lacks effective protection during the existing metal workpiece processing and forming process, which affects the service life of the driving coil.

[0004] The purpose of the present invention is to address the above-mentioned problems and provide a pipe processing method based on a discrete magnetizer, wherein a layer of discrete magnetizer is added between the driving coil and the formed pipe, and the discrete magnetizer is fixedly connected and packaged with the driving coil to enhance the structural strength of the driving coil, so that the electromagnetic field intensity generated by the induced eddy current of the pipe in the driving coil is reduced, thereby protecting the driving coil; the discrete magnetizer comprises a first magnetizer ring and a second magnetizer ring, wherein the first magnetizer ring is arranged at the end of the pipe forming zone, and the cross-sectional area of ​​the first magnetizer ring is larger than the cross-sectional area of ​​the second magnetizer ring, thereby increasing the radial electromagnetic force on the end of the pipe forming zone, so that the uniformity of the forming zone is better after the pipe is formed, and the pipe forming effect is improved.

[0005] In order to achieve the above object, the technical solution provided by the present invention is: A pipe processing method based on a discrete magnetizer is provided between a driving coil for providing an electromagnetic field and the pipe to be expanded, the discrete magnetizer comprises a first magnetizer ring and a second magnetizer ring, the cross-sections of the first magnetizer ring and the second magnetizer ring are both trapezoidal, the lower base of the trapezoid is adjacent to the outer edge of the driving coil, and the cross-sectional area of ​​the first magnetizer ring is greater than the cross-sectional area of ​​the second magnetizer ring.

[0006] The pipe processing method comprises the following steps: Step 1: Determine the parameters of the driving coil according to the material and forming specifications of the pipe to be formed; Step 2: According to the parameters of the driving coil, the number and size parameters of the first magnetic collector ring and the second magnetic collector ring are determined respectively to manufacture discrete magnetic collectors; Step 3: According to the drive coil parameters obtained in step 1, the copper wire is wound on the reinforcement layer to form a coil, and each layer of the coil is fixed with a reinforcement layer to enhance the structural strength of the coil to form a drive coil, and the discrete magnetic collector is fixedly connected to the outer surface of the drive coil by using reinforcement materials and packaged into one; Step 4: Use a mold to fix the pipe to be formed, and place and fix the discrete magnetic collector and the driving coil coaxially with the pipe to be formed; Step 5: Connect the drive coil to the pulse power supply via the switch, control the air switch to power the drive coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the tube to be bulged; Step 6: Determine whether the bulging area of ​​the tube meets the forming specifications. If so, end the process; if not, execute step 5 and bulge the tube again until the bulging area of ​​the tube meets the forming specifications.

[0007] Preferably, both the first magnetism collector ring and the second magnetism collector ring are provided with slits.

[0008] Preferably, in step 1, finite element software is used to construct a tube electromagnetic bulging simulation model including a driving coil and a tube, a pulse current is applied to the driving coil of the tube electromagnetic bulging simulation model, the bulging effect of the tube is simulated, the parameters of the driving coil are adjusted so that the tube bulging effect meets the forming specification requirements, and the parameters of the driving coil are determined by simulation.

[0009] Furthermore, in step 2, a first magnetizer ring and a second magnetizer ring are added to the electromagnetic bulging simulation model of the pipe, and the electromagnetic bulging simulation model of the pipe is used again to perform the pipe bulging simulation, and the size parameters of the first magnetizer ring and the second magnetizer ring are adjusted to achieve the best bulging effect for the pipe, and the optimal parameters of the first magnetizer ring and the second magnetizer ring are obtained.

[0010] The upper base length of the trapezoidal cross section of the first magnetic collector ring is d11, the lower base length is d12, 2d11 <d12。

[0011] The upper base length of the trapezoidal cross section of the second magnetic collector ring is d21, and the lower base length is d22, 2d21 <d22。

[0012] Preferably, the distance between the first magnetism collector ring and the driving coil is no greater than 2 mm, and the distance between the second magnetism collector ring and the driving coil is no greater than 2 mm.

[0013] Preferably, the distance between the first magnetic concentrator ring and the tube to be expanded is no more than 3 mm.

[0014] Preferably, in step 5, the discharge pulse width of the pulse power supply is 50-1000 μs.

[0015] Preferably, the material of the discrete magnetic collector is consistent with the material of the driving coil wire, and the yield strength of the discrete magnetic collector is greater than 310 MPa.

[0016] The processing device of the above-mentioned pipe processing method based on discrete magnetic collectors includes a driving coil, a discrete magnetic collector and a pulse power supply. The discrete magnetic collector includes a first magnetic collector ring and a second magnetic collector ring. The cross-sections of the first magnetic collector ring and the second magnetic collector ring are both trapezoidal. The first magnetic collector ring is arranged at the end of the expansion zone of the pipe, and the first magnetic collector ring and the second magnetic collector ring are arranged along the outer surface of the driving coil; the driving coil is connected to the pulse power supply via a switch.

[0017] Compared with the prior art, the beneficial effects of the present invention include: 1) The present invention provides a layer of discrete magnetic concentrator between the driving coil and the formed pipe, and packages the discrete magnetic concentrator and the driving coil into one body, thereby effectively enhancing the structural strength of the driving coil, reducing the intensity of the electromagnetic field generated in the driving coil due to the induced eddy current of the pipe, and fundamentally weakening the electromagnetic force on the driving coil without affecting the forming effect, thereby better protecting the driving coil and extending the service life of the driving coil.

[0018] 2) The present invention adopts a discrete magnetic collector to enhance the structural strength of the coil and utilizes a reinforcing material to encapsulate the magnetic collector and the driving coil into one body. Under the premise of not affecting the forming effect, the temperature rise of the coil is reduced, the temperature rise problem of the coil during the electromagnetic forming process of the workpiece is solved, and the service life of the driving coil is extended.

[0019] 3) The present invention arranges a magnetic collector ring with a larger cross-sectional area at the end of the workpiece forming zone, thereby effectively increasing the electromagnetic force on the end of the workpiece forming zone, making the forming zone more uniform after the workpiece is formed, and solving the problem of the end effect affecting the workpiece forming quality during the workpiece forming process.

[0020] 4) The discrete magnetic concentrator of the present invention is easy to manufacture, low in cost, and economical. Its size and cross-sectional shape can be flexibly adjusted according to the requirements of pipe forming, which can effectively improve the uniformity of pipe forming, reduce the curvature of pipe forming, and improve the surface quality of formed pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0022] Figure 1 Schematic diagram of the pipe processing device of Example 1.

[0023] Figure 2 Schematic diagram of the pipe flanging device of the second embodiment.

[0024] Figure 3 Schematic diagram of the structure of discrete magnetic collector and driving coil.

[0025] Figure 4 It is a comparison diagram of the radial electromagnetic force density distribution of the driving coil during the tube processing process of the method of the present invention in Example 1 and the tube bulging method without a discrete magnetic concentrator.

[0026] Figure 5 This is a comparison diagram of the radial electromagnetic force density peak values ​​of the driving coil at different moments during the tube processing process of the method of the present invention and the tube bulging method without a discrete magnetic concentrator in Example 1.

[0027] Explanation of the reference numerals: discrete magnetism collector 1 , first discrete magnetism collector 101 , second discrete magnetism collector 102 , discrete magnetism collector slit 103 , driving coil 2 , coil reinforcement layer 3 , pipe to be processed 4 , pipe forming area 401 . DETAILED DESCRIPTION

[0028] Embodiment 1 like Figure 1 As shown, the pipe processing device based on the discrete magnetism collector includes a discrete magnetism collector 1, a driving coil 2, a pulse power supply and a pipe 4 to be processed. The discrete magnetism collector 1 includes a first magnetism collector ring 101 and a second magnetism collector ring 102. The first magnetism collector ring 101 and the second magnetism collector ring 102 are both provided with a slit 103. The first magnetism collector ring 101 is arranged at the end of the pipe forming area 401. The first magnetism collector ring 101 and the second magnetism collector ring 102 are closely arranged on the outer surface of the driving coil 2, and the first magnetism collector ring 101, the second magnetism collector ring 102 and the driving coil 2 are fixedly connected by a reinforcing material to be sealed as a whole. The cross-sections of the first magnetism collector ring 101 and the second magnetism collector ring 102 are both trapezoidal. The cross-sectional area of ​​the first magnetism collector ring 101 is greater than the cross-sectional area of ​​the second magnetism collector ring 102. The driving coil 1 is connected to the capacitor power supply via an air switch, and when the air switch is controlled to be turned on, eddy currents are induced in the pipe 4 to be processed. The first magnetic concentrator ring 101 increases the electromagnetic force on the end of the expansion zone of the tube 4, so that the uniformity of the forming zone of the tube after expansion is better.

[0029] The length of the upper base of the trapezoidal cross section of the first magnet collector ring is d 11 , the length of the lower base is d 12 ; The length of the upper base of the trapezoidal cross section of the second magnet ring is d 21 , the length of the lower base is d 22 .

[0030] In the embodiment, d 11 = 3d 12 , d 12 =2.5d 11 , d 22 =2.5d 21 .

[0031] The distance between the first magnetic collector ring 101 and the second magnetic collector ring 102 and the outermost layer of the driving coil is equal to 1mm, and the distance between the first magnetic collector ring and the pipe to be processed is 4mm. The cross-sectional diameter of the driving coil wire is 3mm, the thickness of the pipe is 2mm, and the height is 50mm. The yield strength of the discrete magnetic collector is greater than 310MPa, and the discharge pulse width of the pulse power supply is 150μs.

[0032] The pipe processing method based on discrete magnetic concentrator includes the following steps: Step 1: Determine the parameters of the driving coil according to the material and forming specifications of the pipe to be processed; Step 2: According to the parameters of the driving coil, the number and size parameters of the first magnetic collector ring and the second magnetic collector ring are determined respectively to manufacture discrete magnetic collectors; Step 3: According to the drive coil parameters obtained in step 1, the copper wire is wound on the reinforcement layer to form a coil, and each layer of the coil is fixed with a reinforcement layer to enhance the structural strength of the coil to form a drive coil, and the discrete magnetic collector is fixedly connected to the outer surface of the drive coil by using reinforcement materials and packaged into one; Step 4: Use the mold to fix the pipe to be processed, and place and fix the discrete magnetic collector and the driving coil coaxially with the pipe to be processed; Step 5: Connect the drive coil to the pulse power supply via the switch, control the air switch to power the drive coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the tube to be bulged; Step 6: Determine whether the bulging area of ​​the tube meets the forming specifications. If so, end the process; if not, execute step 5 and bulge the tube again until the bulging area of ​​the tube meets the forming specifications.

[0033] In the embodiment, a pipe processing method based on a discrete magnetic concentrator, that is, the method of the present invention, is compared with a traditional pipe bulging processing method without a discrete magnetic concentrator by simulation experiment. The pulse voltage of the simulation experiment is set to 4kV, and the circuit parameters of the driving coil are the same.

[0034] The driving coil is mainly affected by radial electromagnetic force during the tube bulging process, and the axial electromagnetic force is not large. In order to observe and compare the two-dimensional distribution of electromagnetic force density in the driving coil, the driving coil in the simulation experiment uses a copper wire with a rectangular cross section. Figure 4 The left side shows the radial electromagnetic force density distribution of the driving coil in the traditional tube bulging method without a discrete magnetic concentrator. Figure 4 The right side shows the radial electromagnetic force density distribution of the driving coil of the method of the present invention. Figure 4 It can be seen that no matter it is the traditional tube bulging method or the method of the present invention, the radial electromagnetic force density on the inner side of the driving coil during the tube bulging process is greater; compared with the traditional tube bulging method, the present invention uses a discrete magnetic collector to greatly weaken the radial electromagnetic force density on the inner side of the driving coil, thereby playing a role in protecting the driving coil.

[0035] The peak value of the radial electromagnetic force density of the driving coil during the tube bulging process of the method of the present invention and the conventional tube bulging method without a discrete magnetic collector is as follows: Figure 5 As shown. Figure 5By comparison, it can be seen that the method of the present invention reduces the peak value of the radial electromagnetic force density of the drive coil by about 45%. Obviously, for a drive coil with the same material parameters, the method of the present invention can greatly reduce the radial electromagnetic force on the drive coil, thereby protecting the coil and increasing the service life of the coil.

[0036] Embodiment 2 The difference from the first embodiment is that the second embodiment uses a discrete magnetic concentrator in cooperation with a driving coil to perform flanging processing on the pipe.

[0037] like Figure 2 As shown, the pipe flanging device based on discrete magnetism collector includes a discrete magnetism collector 1, a driving coil 2, a capacitor power supply and a pipe 4 to be processed. The discrete magnetism collector 1 includes a first magnetism collector ring 101 and a second magnetism collector ring 102. The first magnetism collector ring 101 and the second magnetism collector ring 102 are both provided with a slit 103. The first magnetism collector ring 101 is arranged at the end of the pipe forming area 401. The first magnetism collector ring 101 and the second magnetism collector ring 102 are closely arranged on the outer surface of the driving coil 2, and the first magnetism collector ring 101, the second magnetism collector ring 102 and the driving coil 2 are fixedly connected by a reinforcing material to be sealed as a whole. The cross-sections of the first magnetism collector ring 101 and the second magnetism collector ring 102 are both trapezoidal. The cross-sectional area of ​​the first magnetism collector ring 101 is greater than the cross-sectional area of ​​the second magnetism collector ring 102. The driving coil 1 is connected to the capacitor power supply via an air switch, and when the air switch is controlled to be turned on, eddy currents are induced in the pipe 4 to be processed. The first magnetic concentrator ring 101 increases the electromagnetic force on the end of the forming zone of the pipe 4, so that the forming zone of the pipe 4 is smoother and more uniform after flanging.

[0038] The length of the upper base of the trapezoidal cross section of the first magnet collector ring is d 11 , the length of the lower base is d 12 ; The length of the upper base of the trapezoidal cross section of the second magnet ring is d 21 , the length of the lower base is d 22 .

[0039] In the embodiment, d 12 =2.5d 11 , d 22 =2.5d 21 , d 11 = 2d 12 .

[0040] The distance between the first magnetic collector ring 101, the second magnetic collector ring 102 and the outermost layer of the driving coil is equal to 1mm, and the distance between the first magnetic collector ring and the pipe to be processed is 3mm. The cross-sectional diameter of the driving coil wire is 3mm, the thickness of the pipe is 2mm, and the height is 50mm. The yield strength of the discrete magnetic collector is greater than 310MPa, and the discharge pulse width of the pulse power supply is 150μs.

[0041] The pipe flanging method based on discrete magnetic concentrators comprises the following steps: Step 1: Determine the parameters of the driving coil 2 according to the material and forming specifications of the pipe to be processed; Finite element software is used to construct a pipe electromagnetic flanging simulation model including a driving coil and a pipe. A pulse current is applied to the driving coil of the pipe electromagnetic flanging simulation model to simulate the flanging effect of the pipe. The parameters of the driving coil are adjusted to make the flanging effect of the pipe meet the forming specifications, and the parameters of the driving coil are determined by simulation.

[0042] Step 2: According to the parameters of the driving coil, the number and size parameters of the first magnetism collector ring 101 and the second magnetism collector ring are determined respectively to manufacture a discrete magnetism collector 1 .

[0043] The first magnetizer ring and the second magnetizer ring are added to the electromagnetic flanging simulation model of the pipe fitting, and the electromagnetic flanging simulation model of the pipe fitting is used again to perform the pipe flanging simulation. The size parameters of the first magnetizer ring and the second magnetizer ring are adjusted to achieve the best flanging effect of the pipe fitting, and the optimal parameters of the first magnetizer ring and the second magnetizer ring are obtained.

[0044] Step 3: According to the drive coil parameters obtained in step 1, the copper wire is wound on the coil reinforcement layer 3 to form a coil, and each layer of the coil is fixed with a reinforcement layer to enhance the structural strength of the coil to form a drive coil 2, and the discrete magnetic collector is fixedly connected to the outer surface of the drive coil by using reinforcement materials and packaged into one; Step 4: Use the mold to fix the pipe to be processed, and place and fix the discrete magnetic collector and the driving coil coaxially with the pipe to be processed; Step 5: Connect the drive coil to the pulse power supply via the switch, control the air switch to power the drive coil, control the discharge time of the pulse power supply, and perform electromagnetic flanging on the pipe to be processed; Step 6: Determine whether the forming area of ​​the pipe fitting meets the forming specifications. If so, end the process; if not, execute step 5 and perform flanging on the pipe fitting again until the forming area of ​​the pipe fitting meets the forming specifications.

[0045] The implementation results show that the present invention improves the flatness of the flange area of ​​the pipe fitting, effectively solves the problem of pipe flange buckling caused by the end effect, and utilizes the discrete collecting magnetic field to enhance the structural strength of the driving coil, reduce the temperature rise of the driving coil, and reduce the electromagnetic force applied to the driving coil during the pipe processing, thereby protecting the coil and extending the service life of the driving coil.

Claims

1. A pipe processing method based on a discrete magnetic concentrator, characterized in that: A discrete magnetism collector is arranged between a driving coil for providing an electromagnetic field and the tube to be expanded, the discrete magnetism collector comprises a first magnetism collector ring and a second magnetism collector ring, the cross sections of the first magnetism collector ring and the second magnetism collector ring are both trapezoidal, the lower bottom edge of the trapezoid is close to the outer edge of the driving coil, the cross section area of ​​the first magnetism collector ring is larger than the cross section area of ​​the second magnetism collector ring, after the driving coil is energized, the electromagnetic field generated by the induced eddy current in the tube generates induced eddy currents on the discrete magnetism collector, and the induced eddy current density on the inner surface of the discrete magnetism collector is smaller than the induced eddy current density on the outer surface, so that the electromagnetic field intensity generated by the induced eddy current of the tube in the driving coil is reduced, thereby protecting the driving coil; at the same time, the first magnetism collector ring arranged at the end of the tube expansion zone increases the radial electromagnetic force on the end of the tube expansion zone, improves the end effect of the tube expansion, and makes the tube expansion zone more uniform after forming; The pipe processing method comprises the following steps: Step 1: Determine the parameters of the driving coil according to the material and forming specifications of the pipe to be formed; Step 2: According to the parameters of the driving coil, the number and size parameters of the first magnetic collector ring and the second magnetic collector ring are determined respectively to manufacture discrete magnetic collectors; Step 3: According to the drive coil parameters obtained in step 1, the copper wire is wound on the reinforcement layer to form a coil, and each layer of the coil is fixed with a reinforcement layer to enhance the structural strength of the coil to form a drive coil, and the discrete magnetic collector is fixedly connected to the outer surface of the drive coil by using reinforcement materials and packaged into one; Step 4: Use a mold to fix the pipe to be formed, and place and fix the discrete magnetic collector and the driving coil coaxially with the pipe to be formed; Step 5: Connect the drive coil to the pulse power supply via the switch, control the air switch to power the drive coil, control the discharge time of the pulse power supply, and perform electromagnetic bulging on the tube to be bulged; Step 6: Determine whether the bulging area of ​​the tube meets the forming specifications. If so, end the process; if not, execute step 5 and bulge the tube again until the bulging area of ​​the tube meets the forming specifications.

2. The pipe processing method based on discrete magnetic concentrator according to claim 1 is characterized in that: The first magnetism collector ring and the second magnetism collector ring are both provided with slits.

3. The pipe processing method based on discrete magnetic concentrator according to claim 2 is characterized in that: In step 1, finite element software is used to construct a tube electromagnetic bulging simulation model including a driving coil and a tube, a pulse current is applied to the driving coil of the tube electromagnetic bulging simulation model, the bulging effect of the tube is simulated, the parameters of the driving coil are adjusted so that the tube bulging effect meets the forming specifications, and the parameters of the driving coil are determined by simulation.

4. The pipe processing method based on discrete magnetic concentrator according to claim 3 is characterized in that: In step 2, the first magnetizer ring and the second magnetizer ring are added to the electromagnetic bulging simulation model of the pipe fitting, and the pipe bulging simulation is performed again using the electromagnetic bulging simulation model of the pipe fitting. The size parameters of the first magnetizer ring and the second magnetizer ring are adjusted to achieve the best bulging effect of the pipe fitting, and the optimal parameters of the first magnetizer ring and the second magnetizer ring are obtained.

5. The pipe processing method based on discrete magnetic concentrator according to claim 2 is characterized in that: The upper base length of the trapezoidal cross section of the first magnetic collector ring is d11, the lower base length is d12, 2d11 <d12。 6. The pipe processing method based on discrete magnetic concentrator according to claim 2 is characterized in that: The upper base length of the trapezoidal cross section of the second magnetic collector ring is d21, and the lower base length is d22, 2d21 <d22。 7. The pipe processing method based on discrete magnetic concentrator according to claim 2 is characterized in that: The distance between the first magnetism collector ring and the driving coil is not greater than 2 mm, and the distance between the second magnetism collector ring and the driving coil is not greater than 2 mm.

8. The pipe processing method based on discrete magnetic concentrator according to claim 2 is characterized in that: The distance between the first magnetic collector ring and the tube to be expanded is not more than 3 mm.

9. The pipe processing method based on discrete magnetic concentrator according to claim 2, characterized in that: In step 5, the discharge pulse width of the pulse power supply is 50-1000 μs.

10. A processing device for a pipe processing method based on a discrete magnetic concentrator according to any one of claims 1 to 9, characterized in that: The processing device includes a driving coil, a discrete magnetism collector and a pulse power supply. The discrete magnetism collector includes a first magnetism collector ring and a second magnetism collector ring. The cross-sections of the first magnetism collector ring and the second magnetism collector ring are both trapezoidal. The first magnetism collector ring is arranged at the end of the expansion zone of the pipe. The first magnetism collector ring and the second magnetism collector ring are arranged along the outer surface of the driving coil. The driving coil is connected to the pulse power supply via a switch.

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