Magnetic shielding device and method for reducing eddy current loss of high-energy-efficiency distribution transformer

Abstract

The invention discloses a magnetic shielding device and method for reducing eddy-current loss of a high-energy-efficiency distribution transformer, and the device comprises an oil tank, a transformer body and a plurality of coils are disposed in the oil tank, reinforcing plates are disposed at the outer sides of the coils at the edge, an oil tank inner shield is disposed at the low-voltage side of the transformer body, and reinforcing plate inner shields are disposed between the reinforcing plates at the two sides of the oil tank and the coils. The oil tank inner shield and the reinforcing plate inner shield are both silicon steel sheet magnetic shields. The oil tank inner shield is consistent with the transformer in design size; the size of the reinforcing plate inner shield is consistent with that of the reinforcing plate; the reinforcing plate inner shields are placed in gaps between the reinforcing plates on the two sides of the oil tank and the coil; holes are formed in the periphery of the oil tank inner shield and fixedly connected with the oil tank through bolts; the silicon steel sheet magnetic shield is formed by wrapping silicon steel sheets with cable paper. Silicon steel sheet magnetic shields are added to the low-voltage side of the oil tank and the inner side of the reinforcing plate respectively, the problem of magnetic field leakage of the transformer can be solved, the performance of the transformer is better, and safe, efficient and lasting operation of the transformer is guaranteed.

Description

Technical Field

[0001] The present invention relates to a magnetic shielding device and method, and in particular to a magnetic shielding device and method for reducing eddy current loss of a high-energy-efficiency distribution transformer. Background Art

[0002] Eddy current is also a kind of induced current. When a coil is wound around an iron core, this coil is equivalent to a primary coil, and the iron core can be regarded as a secondary coil. When a changing current is passed through the primary coil, a changing magnetic flux will be generated in the iron core. Due to the mutual inductance, a self-circulating current will be generated in the iron core, which is an eddy current. Eddy current will cause the iron core to heat up and increase the loss of electric energy, which is called eddy current loss.

[0003] The transformer core eddy current is the electric field induced in the silicon steel sheet by the magnetic lines of force in the primary coil when passing through the core, and because the magnetic field is a magnetic field with a gradient, the induced electric field is also the same. The different electric field strengths induced between the gradients lead to a potential difference, thus generating eddy currents. The intensity of the eddy current is also related to the thickness and magnetic permeability of the silicon steel sheet. Therefore, the higher the magnetic permeability and the thinner the thickness of the silicon steel sheet, the smaller the eddy current it generates, that is, the smaller the no-load loss of the transformer.

[0004] The presence of eddy currents in motors and transformers will cause heat loss in the core and weaken the magnetic field, resulting in reduced efficiency of electrical equipment and insufficient capacity. Transformer magnetic field leakage will not only cause energy loss, but also cause local overheating of transformer structural parts, affecting the efficiency and normal operation of the transformer. In the long run, it will cause local insulation aging of the transformer, shorten the life of the transformer, and in severe cases threaten the safe operation of the transformer. Reasonable control of magnetic leakage in transformer structural parts can improve the performance of the transformer and ensure its safe, efficient and long-term operation. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to propose a magnetic shielding device and method for reducing eddy current loss of high-efficiency distribution transformers, so as to solve the problem of transformer leakage magnetic field.

[0006] Technical solution: The present invention includes an oil tank, in which a device body and multiple coils are arranged. A reinforcing plate is arranged on the outer side of the coil located at the edge. It is characterized in that an inner shield of the oil tank is installed on the low-voltage side of the device body, and an inner shield of the reinforcing plate is placed between the reinforcing plates on both sides of the oil tank and the coils. The inner shield of the oil tank and the inner shield of the reinforcing plate are both magnetically shielded by silicon steel sheets.

[0007] The inner shield of the oil tank is consistent with the design size of the transformer so as not to affect the inlet and outlet of the transformer oil.

[0008] The inner shielding dimension of the reinforcing plate is consistent with the dimension of the reinforcing plate.

[0009] The inner shield of the reinforcing plate is placed at the gap between the reinforcing plate and the coil on both sides of the oil tank.

[0010] The inner shield of the oil tank has holes around it and is fixedly connected to the oil tank by bolts. Since the magnetic density distribution of the oil tank is mainly concentrated on the inner side of the oil tank next to the low pressure, the inner shield of the oil tank is only installed on the low pressure side of the oil tank.

[0011] The silicon steel sheet magnetic shielding is composed of the silicon steel sheet wrapped with cable paper.

[0012] A magnetic shielding method for reducing eddy current loss of a high-efficiency distribution transformer comprises the following steps:

[0013] S1. Make magnetic shielding of silicon steel sheets. Wrap all the silicon steel sheets with cable paper. Punch holes for the magnetic shielding of silicon steel sheets on the low-voltage side of the transformer. No holes are needed for the magnetic shielding of silicon steel sheets on the inner side of the reinforcement plate.

[0014] S2. The shield inside the reinforcing plate does not need to be punched and fixed. The size of the shield inside the reinforcing plate is consistent with the size of the reinforcing plate and is placed in the gap between the coil and the reinforcing plate;

[0015] S3. Bolts are reserved in the oil tank. On the low-pressure side of the oil tank, the punched silicon steel sheet magnetic shield is fixed in the oil tank with nuts;

[0016] S4. Lift the transformer body into the oil tank, and after ensuring that the magnetic shielding of the silicon steel sheet is not damaged, lift it to the bottom of the tank.

[0017] An oil tank equipped with a magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer, wherein a device body and multiple coils are arranged in the oil tank, a reinforcing plate is arranged outside the coils located at the edge, an oil tank inner shield is installed on the low-voltage side of the device body, and a reinforcing plate inner shield is placed between the reinforcing plates on both sides of the oil tank and the coils.

[0018] The inner shield of the oil tank and the inner shield of the reinforcement plate both adopt silicon steel sheet magnetic shielding, which is composed of cable paper wrapped silicon steel sheet.

[0019] The inner shield of the oil tank is consistent with the design size of the transformer.

[0020] The inner shielding dimension of the reinforcing plate is consistent with the dimension of the reinforcing plate.

[0021] Beneficial effect: The present invention can solve the transformer leakage magnetic field problem by adding silicon steel sheet magnetic shielding on the low-voltage side of the oil tank and the inner side of the reinforcement plate, thereby improving the performance of the transformer and ensuring its safe, efficient and long-lasting operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 is the magnetic induction intensity distribution diagram in the fuel tank;

[0024] Figure 3 This is the magnetic induction intensity distribution diagram of the reinforcement plate. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] like Figure 1 As shown, the magnetic shielding device for reducing eddy current loss of high-efficiency distribution transformer of the present invention comprises an oil tank 1, a body 2 and a plurality of coils 8 are arranged in the oil tank 1, a reinforcing plate 6 is arranged outside the coils 8 located at the edge, an oil tank inner shield 3 is installed on the low-voltage side of the body 2, and reinforcing plate inner shields 4 are placed between the reinforcing plates 6 and the coils 8 on both sides of the oil tank 1. The oil tank inner shield 3 and the reinforcing plate inner shield 4 are both magnetically shielded by silicon steel sheets, and are composed of cable paper wrapped around the silicon steel sheets. The oil tank inner shield 3 has holes around it and is fixedly connected to the oil tank 1 by bolts.

[0027] According to the magnetic density distribution, silicon steel sheet magnetic shielding is added on the low-voltage side of the oil tank 1 and the inner side of the reinforcement plate 6 respectively. Since the magnetic density distribution of the oil tank is mainly concentrated on the inner side of the oil tank next to the low voltage, the inner shield 3 of the oil tank is only installed on the low-voltage side of the oil tank. At the same time, since the position of the corrugated sheet is relatively high, in order not to affect the inlet and outlet of the transformer oil, the inner shield 3 of the oil tank is consistent with the design size of the transformer; the size of the inner shield 4 of the reinforcement plate is consistent with the size of the reinforcement plate 6.

[0028] As shown in Table 1, the eddy current loss is mainly concentrated in the fuel tank, reaching 44.83W, accounting for 48%, followed by the reinforcement plates on both sides, accounting for 28%, and the losses of other components are relatively low.

[0029] Table 1 Loss results without magnetic shielding

[0030]

[0031] from Figure 2 and Figure 3 From the distribution of magnetic induction intensity, it can be seen that the loss of the oil tank is mainly concentrated on the inner wall of the oil tank next to the winding and the low-voltage side lead copper bar; the loss of the reinforcement plates on both sides is mainly distributed on the side close to the winding, almost covering the entire plane. With the increase of the thickness of the magnetic shielding on the inner side of the oil tank, the eddy current loss gradually decreases, but the reduction is getting smaller and smaller. The eddy current loss of 0.69mm thickness is only about 3.5W less than that of 0.46mm thickness, and the cost performance is low. When the thickness of the oil tank magnetic shielding is 0.46mm + the thickness of the reinforcement plate magnetic shielding is 0.23mm, the loss of the single-sided reinforcement plate is reduced to about 5W, and the total loss is 63.9W, which is 29.6W lower than that without shielding, a decrease of 31.6%, accounting for 0.84% ​​of the transformer load loss. The amount of silicon steel used is about 1.136kg. Calculated at 17 yuan / kg, the cost of silicon steel material is about 19.3 yuan.

[0032] A magnetic shielding method for reducing eddy current loss of a high-efficiency distribution transformer of the present invention comprises the following steps:

[0033] S1. Make magnetic shielding of silicon steel sheets. Wrap all the silicon steel sheets with cable paper. The magnetic shielding of silicon steel sheets on the low-voltage side of the transformer needs to be punched and fixed. The magnetic shielding of silicon steel sheets on the inner side of the reinforcement plate does not need to be punched.

[0034] S2, the shield 4 inside the reinforcing plate does not need to be punched and fixed. The size of the shield inside the reinforcing plate is consistent with the size of the reinforcing plate, and it can be placed in the gap between the coil and the reinforcing plate;

[0035] S3. Bolts are reserved in the oil tank. On the low-pressure side of the oil tank, the punched silicon steel sheet magnetic shield is fixed in the oil tank with nuts;

[0036] S4. Slowly lift the transformer body into the oil tank with a crane. The transformer body should be in a balanced state, with even force on the transformer body without tilt or squeezing, and the magnetic shielding of the silicon steel sheet should not be damaged before it can be lifted to the bottom of the tank.

Claims

1. A magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer, comprising an oil tank, a body and a plurality of coils are arranged in the oil tank, and a reinforcing plate is arranged outside the coils at the edge, characterized in that: The low-voltage side of the device body is equipped with an oil tank inner shield, and a reinforcing plate inner shield is placed between the reinforcing plates on both sides of the oil tank and the coil. The oil tank inner shield and the reinforcing plate inner shield are both magnetically shielded by silicon steel sheets.

2. A magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer according to claim 1, characterized in that: The inner shield of the oil tank is consistent with the design size of the transformer.

3. A magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer according to claim 1, characterized in that: The inner shielding dimension of the reinforcing plate is consistent with the dimension of the reinforcing plate.

4. A magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer according to claim 3, characterized in that: The inner shield of the reinforcing plate is placed at the gap between the reinforcing plate and the coil on both sides of the oil tank.

5. A magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer according to claim 2, characterized in that: The inner shield of the oil tank has openings around it and is fixedly connected to the oil tank by bolts.

6. A magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer according to claim 1, characterized in that: The silicon steel sheet magnetic shielding is composed of the silicon steel sheet wrapped with cable paper.

7. A magnetic shielding method for reducing eddy current loss of a high-efficiency distribution transformer using any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Make magnetic shielding of silicon steel sheets. Wrap all the silicon steel sheets with cable paper. Punch holes for the magnetic shielding of silicon steel sheets on the low-voltage side of the transformer. No holes are needed for the magnetic shielding of silicon steel sheets on the inner side of the reinforcement plate. S2. The shield inside the reinforcing plate does not need to be punched and fixed. The size of the shield inside the reinforcing plate is consistent with the size of the reinforcing plate and is placed in the gap between the coil and the reinforcing plate; S3. Bolts are reserved in the oil tank. On the low-pressure side of the oil tank, the punched silicon steel sheet magnetic shield is fixed in the oil tank with nuts; S4. Lift the transformer body into the oil tank, and after ensuring that the magnetic shielding of the silicon steel sheet is not damaged, lift it to the bottom of the tank.

8. An oil tank equipped with a magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer, characterized in that: The oil tank is provided with a device body and multiple coils, a reinforcing plate is provided on the outer side of the coil located at the edge, an oil tank inner shield is installed on the low-voltage side of the device body, and a reinforcing plate inner shield is placed between the reinforcing plates on both sides of the oil tank and the coils.

9. An oil tank equipped with a magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer according to claim 8, characterized in that: The inner shield of the oil tank and the inner shield of the reinforcement plate are both magnetically shielded by silicon steel sheets.

10. An oil tank equipped with a magnetic shielding device for reducing eddy current loss of a high-efficiency distribution transformer according to claim 8, characterized in that: The inner shield of the oil tank is consistent with the design size of the transformer; the inner shield size of the reinforcement plate is consistent with the size of the reinforcement plate.

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