Oil-immersed transformer

Abstract

The invention relates to an oil-immersed transformer which is characterized in that a vibrating reed made of magnetostrictive materials is mounted on the inner wall of an oil tank, leakage magnetic field energy generated by a winding and an iron core during operation of the transformer is converted into high-frequency micro-vibration mechanical energy of the vibrating reed, and the vibration energy is rigidly transmitted to an external radiating fin through the wall of the oil tank; and a transformer oil boundary layer on the surface of the cooling fin is damaged, so that self-adaptive heat dissipation enhancement with zero external driving, zero additional energy consumption and no maintenance is realized.

Description

Technical Field

[0001] This invention relates to an oil-immersed transformer. Background Technology

[0002] Existing oil-immersed transformers have long relied on a combination of mechanical oil pump-driven oil circulation or natural convection with static heat exchange fins for heat dissipation. Traditional heat exchange fins, as the core heat exchange component, are all fixed metal fins that achieve heat dissipation by increasing surface area and improving thermal conductivity; essentially, they are passive heat transfer elements. However, regardless of the increase in oil flow rate, a boundary layer with a thickness of 0.1-0.3 mm always exists on the surface of the heat exchange fin, and its thermal resistance accounts for more than 60% of the overall thermal resistance, becoming the core bottleneck restricting heat dissipation efficiency.

[0003] The industry has tried to reduce the boundary layer effect by optimizing fin spacing, adding turbulence columns, and surface coatings, but these are all static improvements. The heat dissipation coefficient of the heat sink is only slightly improved, and it cannot dynamically adapt to changes in transformer load.

[0004] To overcome boundary layer limitations, active enhancement technologies have been proposed, mainly including: ① forced convection with external fans, but this introduces moving parts and energy consumption, and increases system complexity; ② ultrasonic vibration devices, which require high-frequency power supply and face electromagnetic compatibility challenges; ③ electric field-driven fluid micro-disturbances, but these are prone to discharge risks in oil-immersed environments. All these solutions require external energy input and additional control devices, violating the design principles of high reliability and maintenance-free operation for transformer auxiliary equipment.

[0005] The present invention aims to provide a new solution for efficient heat dissipation of oil-immersed transformers. Summary of the Invention

[0006] The purpose of this invention is to improve the dynamic adaptability of the heat dissipation coefficient and heat dissipation capacity of the heat sink of an oil-immersed transformer under the conditions of zero external drive, zero additional energy consumption, and maintenance-free operation.

[0007] The objective of this invention is achieved through the following technical solution: an oil-immersed transformer, comprising an oil tank, an iron core and windings disposed within the oil tank, and an external heat sink for dissipating heat from the circulating oil within the oil tank, characterized in that the heat sink is rigidly connected to the oil tank, and a vibrating plate is disposed within the oil tank, the vibrating plate being made of magnetostrictive material and also rigidly connected to the oil tank (the connection here includes direct connection and connection through other components), and its mechanical resonance frequency is an integer multiple of the fundamental frequency of the leakage magnetic field of the transformer, preferably 1-3 times.

[0008] As a preferred embodiment, the vibrating plate is installed on the side wall of the oil tank. This location facilitates installation of the vibrating plate, and also provides a stronger leakage magnetic field.

[0009] Preferably, the vibrating plate is corrugated, preferably a sine wave, sawtooth wave, or pulse square wave, which increases the surface area of ​​the vibrating plate and helps to optimize its vibration mode.

[0010] Preferably, the vibrating plate is mounted on the side wall of the oil tank via a bracket made of non-magnetic material. The non-magnetic material reduces the transmission of the magnetic field to the tank wall, thus reducing heat generation on the tank wall.

[0011] During transformer operation, the windings and core inevitably generate a leakage magnetic field, with a magnetic flux density reaching 0.02-0.1T near the tank wall. Existing technologies have consistently employed magnetic shielding structures to reduce the impact of this leakage magnetic field. This invention utilizes this leakage magnetic field as a usable energy source. Based on the characteristic that magnetostrictive materials exhibit micron-level strain under a magnetic field, this triggers a vibrating plate to self-excite oscillation. By designing the mechanical resonant frequency of the vibrating plate, this vibration is amplified to a sufficient intensity and then transmitted through the tank wall to the heat sink, causing the heat sink to vibrate and actively disrupt its surface boundary layer, thus reducing thermal resistance. This invention can significantly improve the heat dissipation coefficient of transformer heat sinks under conditions of zero external drive, zero additional energy consumption, and maintenance-free operation. Furthermore, the vibration intensity of the vibrating plate and heat sink automatically increases or decreases with the transformer load, achieving adaptive heat dissipation adjustment without external control, solving the problem that traditional heat sinks cannot dynamically respond to load changes.

[0012] This invention utilizes the inherent leakage magnetic field of the transformer during operation to drive the vibrating sheet of the magnetostrictive material, causing the oil tank and external heat sink to vibrate, thereby achieving heat dissipation enhancement of the transformer with zero external drive, zero additional energy consumption, and maintenance-free operation. Here, zero external drive, zero additional energy consumption, and maintenance-free operation refer only to the technical features of the heat dissipation enhancement part of this invention.

[0013] Beneficial effects:

[0014] 1) This invention converts the energy of the waste leakage magnetic field into the high-frequency micro-vibration mechanical energy of the vibrating plate of the magnetostrictive material, causing the heat sink to vibrate, thereby actively destroying its boundary layer thermal resistance. It can significantly improve the heat dissipation coefficient of the transformer heat sink under the conditions of zero external drive, zero additional energy consumption, and maintenance-free operation, with an improvement of more than 40%, which exceeds the traditional static optimization method and provides a new solution for efficient heat dissipation of transformers.

[0015] 2) The vibration intensity of the vibrating plate and heat sink of the present invention automatically increases or decreases with the transformer load, which improves the dynamic adaptability of the heat dissipation capacity of the transformer heat sink and solves the technical problem that traditional static heat sinks cannot adapt to load changes. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the heat dissipation principle of an oil-immersed transformer according to a preferred embodiment of the present invention.

[0017] Explanation of reference numerals in the attached figures:

[0018] 1. Oil tank; 2. Vibrating plate made of hysteresis material; 3. Fixed bracket; 4. Transformer oil; 5. Winding; 6. Iron core; 7. Heat sink. Detailed Implementation

[0019] This invention solves the core technical problems of high surface boundary layer thermal resistance, inability to adapt to load changes, and the need for external energy for active enhancement technology when using traditional static heat sinks in transformers. It provides a safe, efficient, and power-free new solution for heat dissipation of oil-immersed transformers. The invention will be further described in detail below with reference to specific embodiments.

[0020] In this embodiment, the oil-immersed transformer is as follows: Figure 1 As shown, the transformer includes an oil tank 1, inside which are a winding 5 and an iron core 6. The oil tank 1 is connected to a heat sink 7, and a corrugated vibrating plate 2 is mounted on its inner sidewall via a fixed bracket 3. The vibrating plate 2 is made of magnetostrictive material, and its mechanical resonant frequency is an integer part of the fundamental frequency of the leakage magnetic field of the transformer. Both the vibrating plate 2 and the heat sink 7 are rigidly connected to the oil tank 1.

[0021] The principle behind improving the heat dissipation coefficient of the oil-immersed transformer heat sink in this embodiment is as follows: When the transformer is running, the leakage magnetic field acts on the vibrating plate 2 of the magnetostrictive material on the inner wall of the oil tank 1, exciting its self-excited vibration. Because the frequency of the leakage magnetic field matches the resonant frequency of the vibrating plate 2, efficient energy coupling is generated between the two, so that the vibration has sufficient intensity and is transmitted to the heat sink 7 through the oil tank 1. The air-induced heat sink 7 vibrates synchronously to form a turbulence enhancement zone on the surface, destroying the boundary layer thermal resistance, thereby significantly improving the heat dissipation coefficient of the transformer heat sink under the conditions of zero external drive, zero additional energy consumption, and maintenance-free operation.

[0022] In addition, as the load changes from small to large, the coupling energy also increases from small to large, which is reflected on the vibrating plate. Its vibration intensity automatically increases or decreases with the transformer load. Therefore, compared with traditional static heat sinks, the transformer heat dissipation capacity of this embodiment can better adapt to load changes.

[0023] In this embodiment, the vibrating plate 2 is installed on the inner side wall of the oil tank 1. On the one hand, this position facilitates the installation of the vibrating plate 2, and on the other hand, the leakage magnetic field is stronger at this position.

[0024] In this embodiment, the fixed bracket 3 is preferably made of a non-magnetic material. This material helps to reduce the transmission of the magnetic field to the tank wall and reduce the heating of the tank wall.

[0025] In this embodiment, the vibrating plate 2 is specifically manufactured using Terfenol-D technology. Its corrugated structure increases its surface area and optimizes its vibration modes, ensuring that its mechanical resonant frequency precisely matches the third harmonic frequency (150Hz) of the transformer's leakage magnetic field. Generally, the lower the matching harmonic order, the greater the excitation intensity; conversely, the higher the matching harmonic order, the smaller the excitation intensity. In this embodiment, it is recommended that the mechanical resonant frequency of the vibrating plate 2 be set to 1-3 times the fundamental frequency of the transformer's leakage magnetic field.

[0026] The connection between the vibrating plate 2 and the fixed bracket 3 can be fixed by bolts, strong and reliable adhesive, or welding to ensure that it does not loosen at an amplitude of 0.5mm. The fixed bracket 3 can be fastened to the inner wall of the oil tank by sealing bolts or welding. The above connection requirements ensure that the vibrating plate 2 is rigidly connected to the oil tank wall and that the vibration energy is effectively transmitted.

[0027] In this embodiment, the self-excited vibrating plate is fixed to the inner wall of the oil tank, and the vibration is transmitted to the external heat sink through the rigidity of the oil tank wall. There are no moving parts exposed to the air, the system has a long maintenance-free cycle, high reliability, and a failure rate close to zero.

[0028] In this embodiment, the leakage magnetic field energy drives the vibrating plate 2 to generate self-excited vibration, such as... Figure 1 As shown, the vibration direction is along the normal to the tank wall, and the vibration amplitude can reach 0.1-0.5mm. The vibration energy is transmitted to the external heat sink 7 in the form of elastic waves along the steel plate of the tank wall, causing the heat sink 7 to vibrate under forced vibration. This actively breaks down the 0.1-0.3mm thick boundary layer thermal resistance on its surface, reducing the heat sink's thermal resistance (simulation tests show that even with a vibration amplitude of 0.1mm, the heat sink's thermal resistance reduction is >60%, and the reduction further increases with the increase of vibration amplitude), thus improving heat transfer efficiency. Moreover, the vibration intensity of the vibrating plate 2 automatically increases or decreases with the transformer load. The amplitude is 0.1-0.2mm at a load rate of 30% and 0.3-0.5mm at a load rate of 100%. The vibration amplitude of the heat sink 7 increases or decreases synchronously with the vibrating plate 2, realizing adaptive heat dissipation adjustment without external control, solving the problem that traditional heat sinks cannot dynamically respond to load changes. When the amplitude of the vibrating plate 2 is about 0.1 mm, the amplitude of the heat sink 7 is also about 0.1 mm, and the heat dissipation coefficient of the heat sink 7 is increased by more than 20%. When the amplitude of the vibrating plate 2 is about 0.4 mm, the amplitude of the heat sink 7 is also about 0.4 mm, and the heat dissipation coefficient of the heat sink 7 can be increased by about 42%.

[0029] In this embodiment, the self-excited vibrating plate is arranged on the inner wall of the oil tank, which improves the energy utilization efficiency of the leakage magnetic field by more than 5 times compared with the external type, and does not need to penetrate the oil tank wall, thus not affecting the overall sealing performance of the oil tank.

[0030] This embodiment of the transformer modification scheme is simple, requiring only the addition of vibrating fins to the inner wall of the oil tank and optimization of the connection between the external heat sink and the oil tank. It is highly adaptable to the modification of existing transformers, with a short modification cycle and low cost. The vibration of the vibrating fins is directly transmitted to the external heat sink through a rigid structure, thereby improving the heat dissipation coefficient of the transformer heat sink. There are no electromagnetic compatibility issues, and it does not affect the operation of the transformer's protection devices.

[0031] Overall, this embodiment can significantly improve the heat dissipation efficiency of transformers under the premise of zero energy consumption, maintenance-free operation, and self-adaptation. It is particularly suitable for oil-immersed transformers with voltage levels from 10kV to 1000kV, and provides a new solution for the thermal management of transformers with high reliability, long life and low operating cost.

Claims

1. An oil-immersed transformer, comprising an oil tank, wherein an iron core and windings are disposed within the oil tank, and further comprising external heat sinks for dissipating heat from the circulating oil within the oil tank, characterized in that, The heat sink is rigidly connected to the oil tank. The oil tank is also equipped with a vibrating plate made of magnetostrictive material, which is also rigidly connected to the oil tank. Its mechanical resonance frequency is an integer multiple of the fundamental frequency of the leakage magnetic field of the transformer.

2. The oil-immersed transformer according to claim 1, characterized in that, The mechanical resonance frequency of the vibrating plate is 1-3 times the fundamental frequency of the leakage magnetic field of the transformer.

3. The oil-immersed transformer according to claim 1, characterized in that, The vibrating plate is installed on the side wall of the oil tank.

4. The oil-immersed transformer according to claim 1, characterized in that, The vibrating plate is corrugated.

5. The oil-immersed transformer according to claim 3, characterized in that, The vibrating plate is mounted on the side wall of the oil tank via a non-magnetic material fixing bracket.

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