Resin cast dry-type transformer with three-dimensional coil

 

 

 

According to the implementation rules, the state will identify a number of high-efficiency energy-saving transformer promotion production enterprises, and establish a catalogue of high-efficiency energy-saving transformer manufacturers. For users who purchase the products of high-efficiency energy-saving transformers produced by enterprises in the catalogue, the state will give certain subsidies according to different energy efficiency grades.

 

 

 

According to the current standards, except for amorphous alloy transformers, it is difficult for the common silicon steel structure laminated core distribution transformers to meet the level of 1 and 2 energy efficiency.

 

 

 

The practice of the three-dimensional core transformer has been proved by the relevant manufacturers in Guangdong Haihong that it is easy to meet the requirements of energy efficiency level 2 or even level 1, and has certain potential advantages, which can become a direction of energy saving design of distribution transformer.

 

 

 

1. Development of three-dimensional core transformer

 

 

 

The analysis of each block of products in the first and second batch of publicity list of high efficiency energy-saving distribution transformer of energy-saving products benefiting the people project shows that more than 70 enterprises have passed the energy conservation certification.

 

 

 

Of them, nearly 70 oil immersed transformers and 50 dry transformers. Among the products certified by energy conservation, there are 17 oil immersed transformers with solid core and 6 dry transformers.

 

 

 

From the above certification, it can be seen that some laminated core products can meet the requirements of energy efficiency level 2 or even level 1 after adopting high-quality silicon steel and optimized design.

 

 

 

But it is necessary to note that the economy of the laminated core products meeting the energy efficiency standards is often poor, and the loss index is basically met by increasing the input of raw materials. Compared with the laminating core, the three-dimensional core products need to introduce the whole core and winding equipment and technology again, and the investment is large. Therefore, there are not many domestic manufacturers, which is far from becoming the mainstream of energy-saving transformer.

 

 

 

At present, under the promotion of domestic manufacturers of solid core transformers and national energy saving policies, the State Grid and Nanan network have begun to purchase the three-dimensional core transformers and form a certain scale.

 

 

 

Like amorphous alloy transformer, at present, the domestic three-dimensional core transformer is mainly oil immersed transformer.

 

 

 

Taking Haihong, Guangdong Province as an example, the company's overall sales volume in 2011 is about 800million yuan, and the dry transformer is about 200 million yuan, of which the maximum capacity of dry transformer has been 4000kva, the maximum capacity of oil transformer has reached 12500 KVA, and the voltage level is 35 kV.

 

 

 

Recently, Sinoway is committed to the research and development of high voltage and large capacity three-dimensional core transformer and amorphous alloy three-dimensional core transformer, and has achieved preliminary results.

 

 

 

In addition, the domestic manufacturers that have obtained the energy conservation certification of the three-dimensional core dry-type transformer include Jiangxi ethnic Power Technology Co., Ltd., Zhejiang jintriangle, Zhuzhou transformer factory, Changde Tianma Electric complete equipment Co., Ltd.

 

 

 

After Beijing Xinhua acquired baotao in Shanghai as a whole, it mainly engaged in the production and sale of three-dimensional core products manufacturing equipment, oil immersed and dry-type three-dimensional core transformers, and in general distribution transformers

 

 

 

2. The characteristics of the solid core

 

 

 

The three-dimensional core is a winding type core, and the whole core is made up of three identical single frames. After the assembly, the three core columns of the core are arranged in three-dimensional arrangement of equilateral triangle. Each single frame is made of several trapezoid material strips, which are coiled in succession. The cross section of the single frame after winding is close to semicircular, and the cross section after the splicing is nearly circular quasi polygon.

 

 

 

Compared with the laminating core, the core has the following advantages:

 

 

 

First, the silicon steel can be used by cutting almost 100% in longitudinal shear, and the residual material of the side angle is less.

 

 

 

Secondly, the silicon steel sheet can be wound tightly and without joints, and the core filling coefficient is high and the magnetic resistance is small. Thirdly, continuous winding can ensure that the direction of magnetic conduction of silicon steel is consistent with the actual magnetic flux direction. Fourth, the length of three-phase magnetic circuit of the three-phase core of the three-dimensional winding core is consistent, so that the three-phase magnetic circuit can be fully balanced.

 

 

 

But there are also several weaknesses in the design and process of the solid core: first, the area of the yoke is only half of the core area, but the yoke flux is 0.57735 times of the core magnetic flux, so the yoke magnetic density is 1.1547 times of the core magnetic density.

 

 

 

In order to ensure the no-load characteristics and noise level of transformer, the magnetic density of core should not be too high.

 

 

 

Secondly, the three-dimensional core must be annealed after winding. The annealing process is very important, but different cores are different, so it is difficult to master, and special annealing equipment is needed.

 

 

 

Third, because the core of the three-dimensional roll can not be opened (Haihong has done experiments, the noise is large after opening and the no-load characteristics become bad), the coil can only be wound with the core, poured and solidified. Special winding equipment is needed for coil winding, and the transformer has a large weight of sequence.

 

 

 

Fourth, the space of the winding gear should be considered when winding, the distance between yoke and coil should be increased, and the mold installation and disassembly space should be considered for casting change. Fifth, the coil can not be disassembled (especially the pouring coil) after the transformer is manufactured, and the repairability of the transformer is poor.

 

 

 

Compared with the dry type transformer with laminated core resin, the main advantages of the three-dimensional roll core resin pouring transformer are low cost and good no-load characteristics, but there are also some disadvantages

 

 

 

First, the height of the three-dimensional core resin pouring transformer is high, but the height of the existing low-voltage switchgear is generally fixed at 2200 m / N. too high transformer will lead to the inconsistency with the height of the low-voltage cabinet when it is combined with the cabinet.

 

 

 

Too high transformer height will lead to insufficient lifting height of distribution room, which will bring difficulties to installation and disassembly of electrical equipment. Second, the depth direction of transformer cabinet is increased.

 

 

 

Because the transformer cabinet is generally deeper than the low voltage cabinet, the gap between the two is further widened. The design of the distribution room is difficult to arrange and the space utilization rate is low.

 

 

 

Third, the three-dimensional roll iron core production plant has little marketing power to the product, and it must pay a certain price to obtain market recognition.

 

 

 

The following data are obtained by consulting the relevant data: the filling coefficient of solid core can reach 0.95-0.96, about 3.5% ~ 5% larger than the stacked core, the utilization rate of core is about 4% higher than that of the stack core, and the process coefficient after annealing can be reduced by 15%, so the weight of silicon steel can be saved by about 10%. The distance between the coil and yoke should be increased for winding, which will increase the silicon steel consumption by about 5%.

 

 

 

By combining the above factors, the weight of silicon steel with the same no-load characteristics can be saved by about 12%.

 

 

 

If the silicon steel used in the solid roll core is the same as that of the lamination core, the no-load property can be improved by about 10%. However, it must be noted that the cost of the core will increase because of the need for annealing, considering the stability of annealing process.

 

 

 

3. Key links in production of dry type transformer with resin casting in solid core

 

 

 

Compared with the ordinary laminated core transformer, the main difference is that the core must be annealed after winding, and the finished iron core products cannot be opened. The core must be operated with the core when winding and casting solidification. The main difficulties in R & D and production of three-dimensional core transformer are summarized and analyzed

 

 

 

First, annealing technology of solid roll core. Because of the different size of core structure, the annealing process is different. Even if the technology introduction contains these contents, we need our company to form its own annealing process according to the actual situation.

 

 

 

Secondly, the coil dfsdf must be wound on the core. If the coil is wound separately at high and low pressure, it is difficult to fix the coil and load and unload the mold. Zhonghao will transfer the mold technology with compensation when technology transfer. The key is how to improve the operation efficiency and effective protection during operation.

 

 

 

If the coil is wound in one, a new winding equipment is needed. The open type three-dimensional core can solve the above problems, but the production efficiency of the core is not improved by Haihong company, but the performance of the product is greatly deteriorated.

 

 

 

Third, the three coils are poured simultaneously during pouring. Because the end cutting and large machining are not allowed, it is difficult to finish and clean the transformer. Fourth, once the product fails, the whole transformer may be scrapped because the resin pouring coil cannot be disassembled.

 

 

 

4. Conclusion

 

 

 

In addition to the same place as winding and pouring, the production of three-dimensional core transformer and the current production of the company is the same, the company also needs to introduce a complete set of technology and provide independent production and operation site. From the technical difficulty, the main problem is the guarantee of process and tooling equipment. As long as the process coefficient is determined in design, the design difficulty is not very big.

 

 

 

From the market, the three-dimensional core has not become the mainstream product of distribution transformer.

 

 

 

With the gradual solution of the material problem of amorphous alloy transformer, it has become the main force of energy-saving transformer. If the amorphous alloy transformer can solve the volume, magnetic characteristics of the core and the dynamic stability of the transformer, the transformer will also have a good market prospect.

 

 

 

Although the three-dimensional core transformer has the advantages of price and performance in a certain capacity section, its process and structure complexity, low production efficiency, technical control and the current plant and equipment condition of the company restrict the implementation of the project.