Device and method for measuring magnetic properties of annular iron core specimens under clamping force

Abstract

The present invention provides a magnetic property measuring device and a measuring method of an iron core annular sample under clamping force, wherein the four corners and the center of the upper clamping plate and the lower clamping plate are provided with through holes correspondingly, and the upper and lower corresponding through holes are connected by an elastic connecting screw; the upper screw of the elastic connecting screw, the upper half of the upper screw is located above the upper clamping plate, and the upper half of the upper screw is provided with an upper nut, a range gasket, a gasket, and an upper gasket in sequence from top to bottom; the range gasket is pressed on the upper top surface of the gasket; the elastic connecting screw also includes a lower screw arranged in the through hole of the lower clamping plate, the lower half of the lower screw is located below the lower clamping plate, and the lower half of the lower screw is provided with a lower gasket and a lower nut in sequence from top to bottom; the upper and lower ends of the spring are respectively connected with the hanging hole of the upper screw and the hanging hole of the lower screw. The present invention has better experimental effect when applying a smaller stress, and improves the experimental accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of transformers, and in particular to a device and a method for measuring magnetic properties of an iron core ring sample under consideration of clamping force. Background Art

[0002] The iron core is the main magnetic circuit part of the transformer. It is usually made of hot-rolled or cold-rolled silicon steel sheets with a high silicon content and coated with insulating paint. The iron core and the coils wound on it form a complete electromagnetic induction system. If the distribution transformer is made of a triangular three-dimensional winding structure, it can reduce material costs and have a competitive advantage. When the iron core is assembled and tightened, the preload force is different, the iron core is affected by stress, and the loss and noise will change accordingly. It has become necessary to study the magnetic properties of the iron core ring specimen under clamping force. The traditional strain gauge test method is not applicable when a small stress is applied. Summary of the invention

[0003] The purpose of the present invention is to provide a device and method for measuring the magnetic properties of an annular sample under a clamping force, which is easy to assemble and stable to clamp, according to the testing needs in actual engineering.

[0004] A device for measuring magnetic properties of annular iron core samples under clamping force is provided, comprising an upper clamping plate and a lower clamping plate, wherein a plurality of pads are respectively arranged on the upper clamping plate and the lower clamping plate, wherein the plurality of pads are arranged in a ring shape, wherein a coil is wound around the gaps between the pads, and the test ring sample is sleeved outside the pads;

[0005] The four corners and the center of the upper and lower clamping plates are provided with through holes, and the upper and lower corresponding through holes are connected by elastic connecting screws;

[0006] The elastic connecting screw comprises an upper screw arranged in the through hole of the upper clamping plate, the upper half of the upper screw is located above the upper clamping plate, and the upper half of the upper screw is provided with an upper nut, a range gasket, a gasket, and an upper gasket in sequence from top to bottom; the range gasket is pressed on the upper top surface of the gasket; the lower half of the upper screw is located below the upper clamping plate and is provided with a hanging hole;

[0007] The elastic connecting screw rod also includes a lower screw rod arranged in the through hole of the lower clamping plate, the upper half of the lower screw rod is located above the lower clamping plate and is provided with a hanging hole; the lower half of the lower screw rod is located below the lower clamping plate, and the lower half of the lower screw rod is provided with a lower gasket and a lower nut in sequence from top to bottom;

[0008] The elastic connecting screw rod also includes a spring, and the upper and lower ends of the spring are respectively connected to the hanging hole of the upper screw rod and the hanging hole of the lower screw rod.

[0009] The spring should have a certain stiffness to avoid fatigue caused by repeated tests, which may reduce the clamping force.

[0010] The range gasket passes through the upper screw and is fixed with liquid glue to measure the elongation of the spring, which is named as the range gasket here.

[0011] The spring force application method is as follows: a gasket is placed on the outside of an upper screw rod, the bottom of the gasket is fixed to an upper clamping plate with double-sided tape, a range gasket passes through the upper screw rod and is pressed on the upper part of the gasket, an upper nut is installed on the upper screw rod, and the upper nut is rotated with a wrench to cause the spring to stretch and deform, so as to achieve the purpose of applying a tightening force to the test ring sample.

[0012] Calculate the spring stiffness based on the applied stress and design the spacer length.

[0013] The applied stress range is divided into ten stages. At the beginning of the measurement, the range gasket is tightly attached to the upper clamping plate, so that the spring is not subjected to stress in the initial test state.

[0014] In order to allow the gasket to pass through the upper screw and be fixed under the range gasket, the gasket should be cut off in advance in an area of ​​90°-110°. The angle should be as large as possible to prevent the ring from breaking when excessive stress is applied.

[0015] After each measurement, the upper nut is rotated to extend the spring and a spacer is added to the bottom until the maximum stress is applied and the measurement is completed.

[0016] To prevent the torque generated when rotating the upper nut from changing the strain of the spring, apply lubricating oil to the upper screw.

[0017] The method for measuring the magnetic properties of an iron core ring sample under clamping force includes the following steps:

[0018] First, rotate the upper nut to lift the range gasket, and place a gasket under the range gasket. During the experiment, rotate the upper nut to pull the spring, and the spring stretches to lift the range gasket. At this time, place a gasket underneath, and then rotate the upper nut in the opposite direction to make the range gasket fall. When you can clearly feel the force being unloaded, remove the gasket, and the hole position change operation is completed. Repeat this operation for the remaining four holes, and continue to apply clamping force in the same way until the end of the experiment;

[0019] The elongation of the spring is reflected by the lifting of the gasket, and the relationship between the elongation and the applied pressure is calculated according to the formula.

[0020] The present invention has better experimental effect when applying smaller stress, thereby improving the experimental accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the present invention;

[0022] Figure 2 It is a schematic diagram of the elastic connecting screw structure of the present invention. DETAILED DESCRIPTION

[0023] The specific technical solution of the present invention is described in conjunction with the accompanying drawings.

[0024] like Figure 1 As shown, a device for measuring magnetic properties of annular iron core samples under clamping force is provided, comprising an upper clamping plate 1 and a lower clamping plate 2, wherein a plurality of pads 4 are respectively arranged on the upper clamping plate 1 and the lower clamping plate 2, wherein the plurality of pads 4 are arranged in a ring shape, a coil 5 is wound on the pads 4, and a test ring sample 3 is sleeved outside the pads 4;

[0025] The four corners and the center of the upper clamping plate 1 and the lower clamping plate 2 are provided with through holes, and the upper and lower corresponding through holes are connected by elastic connecting screws;

[0026] like Figure 2 As shown, the elastic connecting screw comprises an upper screw 6 arranged in the through hole of the upper clamping plate 1, the upper half of the upper screw 6 is located above the upper clamping plate 1, and the upper half of the upper screw 6 is provided with an upper nut 7, a range gasket 8, a gasket 12, and an upper gasket 13 from top to bottom; the range gasket 8 is pressed on the upper top surface of the gasket 12; the lower half of the upper screw 6 is located below the upper clamping plate 1, and is provided with a hanging hole;

[0027] The elastic connecting screw also includes a lower screw 10 arranged in the through hole of the lower clamping plate 2, the upper half of the lower screw 10 is located above the lower clamping plate 2, and is provided with a hanging hole; the lower half of the lower screw 10 is located below the lower clamping plate 2, and the lower half of the lower screw 10 is provided with a lower gasket 14 and a lower nut 11 from top to bottom;

[0028] The elastic connecting screw rod further comprises a spring 9, and the upper and lower ends of the spring 9 are connected to the hanging holes of the upper screw rod 6 and the lower screw rod 10 respectively.

[0029] The upper and lower clamping plates 1 and 2 are rectangular plates made of acrylic material, with holes of about 4-5 mm in size punched in the four corners and the center; the pad 4 is an acrylic block that is narrow inside and wide outside, with a length of 7 mm, a width of 3 mm, and a width of 1.5 mm. The conductor of the coil 5 is a copper wire of equal length of 1 mm and 0.1 mm.

[0030] The upper screw 6 is 4.5 cm long and 3 mm in diameter. A hole with a diameter of 1.5 mm is punched on the side 3 mm away from the lower end.

[0031] First, evenly lay the pad 4 on the lower clamping plate 2 in a circular shape, align the center line with the axis of the circular ring, and fix it with liquid glue 404; then place the test ring sample 3 on the lower clamping plate 2; pass the 1mm copper wire through the gap between the pads, bypass the ring sample and repeat the above work, pay attention to leaving enough margin at the input and output ends for subsequent measurements, and then place the 0.1mm copper wire close to the 1mm copper wire and repeat the previous work, winding the wire in the same direction to avoid wire deviation and damage to the wire after stress is applied; place the upper clamping plate 1 on the upper part, and adjust the coil so that it is just placed in the gap of the pad 4;

[0032] Install the lower nut 11 on the lower half of the lower screw 10 and fix it with glue. The lower screw 10 passes through the through holes of the lower gasket 14 and the lower clamping plate 2. The upper screw 6 passes through the range gasket 8 and then applies lubricating oil on the rod surface. The upper and lower ends of the spring 9 are respectively connected to the circular holes of the upper screw 6 and the lower screw 10. Rotate the upper nut 7 so that the spring 9 is just not subjected to force. The range gasket 8 is fixed to the upper screw 6, which is called the range gasket. Repeat the above work at the other four hole positions.

[0033] After the initial work is completed, the magnetic property experiment without clamping force can be carried out. The method of applying clamping force is as follows: first rotate the upper nut 7, lift the range gasket 8, and place the gasket 12 under the range gasket 8. During the experiment, rotate the upper nut 7 to pull the spring 9, and the spring 9 stretches to lift the range gasket 8. At this time, put the gasket 12 underneath, and then rotate the upper nut 7 in the opposite direction to make the range gasket 8 fall. When the unloading force is obviously felt, remove the gasket 12, and the hole position change operation is completed. The remaining four holes are operated in this way, and the clamping force is continued to be applied in the same way until the end of the experiment. The elongation of the spring 9 is reflected by the lifting of the gasket 12, and the relationship between the elongation and the applied pressure is calculated according to the formula.

[0034] Passing type:

[0035]

[0036] To calculate the voltage, where:

[0037] f——rated frequency, in Hz;

[0038] U——voltage amplitude, unit V;

[0039] B——magnetic flux density, unit T;

[0040] S——Cross-sectional area of ​​the ring specimen, unit ;

[0041] N——Number of coil windings;

[0042] Passing type:

[0043] HL=NI

[0044] To calculate the current, where:

[0045] L——coil magnetic circuit length, unit: m;

[0046] N——number of coil turns;

[0047] H——magnetic field strength, unit A / m;

[0048] The spring design method is as follows:

[0049] Spring stiffness coefficient calculation formula:

[0050]

[0051] G——shear elastic modulus;

[0052] d——wire diameter;

[0053] n——Number of effective coils;

[0054] D——spring middle diameter;

[0055] The measurement is that each 1mm elongation corresponds to one level of stress. After the range gasket 8 is lifted, a gasket 12 is placed underneath. The gasket 12 is cut with an opening of 90°-135°, and then the upper nut 7 is rotated in the opposite direction. When no force is felt, it means that the range gasket 8 has been fitted with the gasket 12, and the stress application process is completed. The operation process for each hole position is the same.

[0056] With the above-mentioned ideal embodiments of the present invention as inspiration, through the above-mentioned description, relevant staff can make various changes and modifications without departing from the technical idea of ​​the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A device for measuring magnetic properties of an iron core ring sample under clamping force, comprising an upper clamping plate (1) and a lower clamping plate (2), wherein a plurality of pads (4) are respectively provided on the upper clamping plate (1) and the lower clamping plate (2), wherein the plurality of pads (4) are arranged in a ring shape, and a coil (5) is wound around the gaps between the pads (4), and the test ring sample (3) is sleeved outside the pads (4); The four corners and the center of the upper clamping plate (1) and the lower clamping plate (2) are provided with corresponding through holes, and the upper and lower corresponding through holes are connected by elastic connecting screws; It is characterized in that The elastic connecting screw comprises an upper screw (6) arranged in a through hole of an upper clamping plate (1); the upper half of the upper screw (6) is located above the upper clamping plate (1); the upper half of the upper screw (6) is provided with an upper nut (7), a range gasket (8), a gasket (12), and an upper gasket (13) in order from top to bottom; the range gasket (8) is pressed on the upper top surface of the gasket (12); the lower half of the upper screw (6) is located below the upper clamping plate (1) and is provided with a hanging hole; The elastic connecting screw further comprises a lower screw (10) arranged in the through hole of the lower clamping plate (2); the upper half of the lower screw (10) is located above the lower clamping plate (2) and is provided with a hanging hole; the lower half of the lower screw (10) is located below the lower clamping plate (2), and the lower half of the lower screw (10) is provided with a lower gasket (14) and a lower nut (11) in order from top to bottom; The elastic connecting screw rod further comprises a spring (9), the upper and lower ends of the spring (9) being respectively connected to the hanging hole of the upper screw rod (6) and the hanging hole of the lower screw rod (10).

2. A method for measuring the magnetic properties of annular core specimens under clamping force, characterized in that: The device for measuring magnetic properties of annular core samples under clamping force as described in claim 1 comprises the following steps: First, rotate the upper nut (7) to lift the range gasket (8), and place the gasket (12) under the range gasket (8). During the experiment, rotate the upper nut (7) to pull the spring (9), and the spring (9) stretches to lift the range gasket (8). At this time, place the gasket (12) underneath, and then rotate the upper nut (7) in the opposite direction to make the range gasket (8) fall. When the force is clearly released, remove the gasket (12). The operation of this hole is completed. The remaining four holes are operated in the same way. Continue to apply clamping force until the experiment is completed. The elongation of the spring (9) is reflected by the lifting of the gasket (12), and the relationship between the elongation and the applied pressure is calculated according to the formula.

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