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How To Solve The Effect Of Silicon Steel Core On Transformer Noise
May 10, 2018

4.1 Reduce vibration source noise

 

   (1) The use of high magnetic permeability materials with small magnetostriction, such as 30ZHl20 silicon steel sheet, can reduce the noise by 4-5dB (A) compared with other materials made of silicon steel sheet.

 

   (2) Reducing magnetic core density can reduce noise. Each decrease of 0.1T in magnetic density can reduce 2-3dB (A). After the noise is reduced but the magnetic density is reduced, the core cross-sectional area, the equivalent capacity of the transformer and the cost are all correspondingly increased, which is not economic from the standpoint of cost. Therefore, reducing the magnetic density cannot exceed 10% of the standard magnetic density.

 

   (3) Improve and reduce core joints. Iron core uses multiple seams. The use of multi-stage joint cores has less noise than two-stage joints, which can reduce the noise by 4-5dB(A). This is because the use of multi-stage (four-stage and above) joints results in a more uniform magnetic flux distribution at the joints, which in turn reduces the magnetic densities in the air gap, resulting in reduced noise due to magnetic attraction at the joints. reason. In addition, reducing the joints can reduce the amplitude, and at the same time reduce the excitation capacity and excitation current of the transformer, so that the sound power is greatly reduced, and the no-load noise can be reduced by 4 to 5 dB(A).

 

   (4) Prevent and reduce the mechanical impact of the silicon steel sheet during processing and production, otherwise it will increase the magnetostriction of the silicon steel sheet, thereby increasing the noise of the iron core.

 

   (5) Epoxy adhesive or polyester adhesive is applied to the core end face to increase the surface tension of the core, and it can also reduce the amount of magnetostriction and reduce noise.

 

    4.2 In absorbing acoustic energy damping

 

   (1) Part of the noise generated by iron core is transmitted through the bottom of the box and the foundation. If a buffer is placed between the body and the tank or between the tank and the foundation, the sound can be attenuated through the buffer. A vibration-proof pad can be placed between the core pad and the magnetic shield and the box wall so that when the vibration of the iron core and the magnetic shield is transmitted to the fuel tank, the steel connection becomes an elastic connection, thereby reducing vibration, preventing resonance, and reducing noise. the goal of. Noise can be reduced by 1-2dB(A).

 

   (2) The acoustic insulation material placed inside the tank reinforcement iron can absorb part of the vibration energy of the tank, so as to reduce the noise of the body and reduce the noise by 2-3dB (A).

 

    4.3 Add Noise Layer to Reduce Noise

 

   According to the structure of the fuel tank, it is divided into two types: modular and high-efficiency. Assembled type: according to the external structure of the fuel tank, the sound insulation board can be made into several pieces, and the sound-absorbing material is placed in the steel plate. Sound-absorbing materials include: rock wool, glass fiber and so on. The sound insulation wall can reflect part of the noise emitted by the transformer body back; and when the noise passes through the sound insulation wall, it can also be absorbed to reduce the noise. The single-piece baffles are bolted to the tank reinforcing iron bolts, respectively, and this baffle plate reduces noise by 10-15dB. Efficient acoustic panels can also be used, placed between two reinforcing irons and secured by thin spring steel plates. The frame-shaped additional weight is used to adjust the vibration characteristics of the high-efficiency sound insulation board, so that its amplitude is significantly lower than that of the reinforcing iron, so that the noise emitted by the transformer body can be effectively shielded and the noise can be reduced by l0-5dB(A).

 

    4.4 Muffler method

 

   Use noise reduction to reduce noise. That is, several noise sounders are placed within the transformer lm so that the noise emitted by them and the noise emitted by the transformer cancel each other out. Its principle is to first transform the noise signal of the transformer into an electric signal, and then amplify the excitation noise generator so that the noise emitted from each noise has the same amplitude and opposite phase, so that the noise of the transformer is subject to destructive interference and the noise can be reduced by 15dB (A )about.

 

    4.5 Other methods

 

   (1) When designing low no-load noise transformers, self-cooling type should be used as far as possible so that the superposition of fan and oil pump noise can be eliminated. When the capacity is difficult to meet the needs, in order to meet the heat dissipation of large-capacity transformers, try to use low-noise submersible pumps and low-speed fan coolers. The use of a low-speed fan can increase the capacity of the self-cooling transformer by 33% and the noise can reach 69dB(A). According to the specific circumstances, two-speed fans can also be used. When the load is low, starting the low-speed fan can reduce the noise correspondingly. When the load is high, the high-speed fan can be turned on, which can increase the capacity of the self-cooled transformer by 67%. At this time, the noise is large, reaching 75dB (A).

 

   (2) When laying out transformers indoors, it should be considered that the noise may increase when reflected on the wall surface. This added value is a function of the ratio of the surface area of the transformer to the surface area of the transformer chamber and is related to the sound absorption coefficient of the wall and the ceiling. Applying slag wool or similar materials to the wall coating can increase the sound absorption coefficient and significantly reduce the noise.

 

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