"Core" becomes "Transformer"

In recent years, the Ministry of Finance, the National Development and Reform Commission, and the Ministry of Industry and Information Technology jointly issued the "Implementation Rules for the Implementation of Energy-Saving Products Huimin Engineering High-Efficiency Energy-Saving Distribution Transformers." It is to promote the consumption of energy-saving products, because China is a big energy-consuming country.

According to the implementing regulations, the state will identify a group of manufacturers that promote the use of high-efficiency energy-saving transformers, and set up a directory of manufacturers of high-efficiency energy-saving transformers. The users of the high-efficiency energy-saving transformer products produced by companies in the procurement catalog will be given certain levels of energy efficiency by the country. Subsidy.

Judging from the current standards, in addition to the amorphous alloy transformers, ordinary iron-cored steel-cored distribution transformers have reached the level of energy efficiency in the Class 1 and 2 standards.

The practice of a three-dimensional wound core transformer with a manufacturing plant based on Guangdong Haihong proves that it is easier to achieve energy efficiency level 2 or even energy efficiency level 1 requirements, and has certain potential advantages, which can be a direction for energy-saving design of distribution transformers.

1. Development of three-dimensional coil core transformer

For the energy-saving products Huimin Engineering High-efficiency Energy-distribution Transformer Promotion Directory, the first and second batch of publicly listed products in the list of products are analyzed, we can see that more than 70 companies across the country have passed energy-saving certification.

There are nearly 70 oil-immersed transformers and nearly 50 dry-type transformers. Among the products that passed the energy-saving certification, there are 17 three-dimensional coil core oil-immersed transformers and six dry-type transformers.

From the above certification, it can be seen that after adopting high-quality silicon steel and optimizing the design, some stacked iron core products can also meet the requirements of energy efficiency class 2 and even energy efficiency class 1.

However, it should be noted that the economical nature of stacked iron core products that meet energy efficiency standards is often poor. Basically, raw material input is used to meet the loss index. Compared with stacked iron cores, three-dimensional rolled iron core products require large investment due to the need to reintroduce the entire iron core and winding equipment and technology. Therefore, there are not many domestic manufacturers and they are far from the mainstream of energy-saving transformers.

At present, under the impetus of domestic manufacturers of three-dimensional coil core transformers and national energy conservation policies, the State Grid and South Network have started to purchase three-dimensional coil core transformers and formed a certain scale.

As with amorphous alloy transformers, current domestic three-dimensional coil core transformers are mainly based on oil-immersed transformers.

Take Guangdong Haihong as an example. In 2011, the company’s overall sales were about 800 million yuan, and the dry change was about 200 million yuan, of which the maximum capacity for dry change has been 4000kVA, the maximum capacity for oil change has reached 12500 kVA, and the highest voltage level is 35 kV.

Recently, Haihong company is committed to the research and development of high-voltage, high-capacity three-dimensional coil core transformer and amorphous alloy three-dimensional coil core transformer. Preliminary results have been obtained.

In addition, domestic manufacturers of three-dimensional coil core dry-type transformers have achieved energy-saving certification of the manufacturers of Han's Han Power Technology Co., Ltd., Zhejiang Golden Triangle, Zhuzhou Transformer Factory, Changde City Tianma Electric Complete Equipment Co., Ltd. and so on.

After Beijing Xinhuadu purchased Shanghai Baotao as a whole, it mainly engaged in the production and sales of three-dimensional coil core product manufacturing equipment, oil-immersed and dry three-dimensional coil core transformers, and was also in general distribution transformers.

2, the characteristics of three-dimensional roll core

The three-dimensional coil core is a wound core, and the entire core is composed of three identical single frames. After the flattening, the three cores of the iron core are arranged in an equilateral triangle configuration. Each single frame is formed by sequentially winding several trapezoidal strips of material, and the cross section of the single frame after winding is close to a semicircular shape. The cross-section is a nearly circular quasi-polygon.

Compared with stacked cores, rolled cores have the following advantages:

First, silicon steel can be used almost 100% through trimming when slitting, and there are fewer corners.

Second, the silicon steel sheet can be wound tightly and seamlessly with high core fill factor and low magnetic resistance. Third, continuous winding can ensure that the magnetic conductivity of silicon steel matches the direction of the actual magnetic flux. Fourth, the length of the three-phase magnetic circuit of the three-dimensional coil core is the same, and the three-phase magnetic circuit can be completely balanced.

However, there are several weaknesses in the design and processing of the three-dimensional coil core. First, the area of ​​the three-dimensional coil core iron yoke is only half of the area of ​​the core column, but the iron yoke flux is 0.57735 times that of the core column flux, so the iron yoke is magnetically dense. The magnetic density of the column is 1.1547 times.

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

Secondly, the three-dimensional coil cores must be annealed after the coiling ends. The annealing process is very important, but the different cores are not the same and it is difficult to master them. Special annealing equipment needs to be configured.

Third, the three-dimensional coil core because the iron core can not be opened (Haechon has done experiments, the noise after opening is larger, the no-load characteristics deteriorate), so the coil can only be wound with a core, casting, curing. Coil winding needs special winding equipment, and the transformer has a large weight in turn.

Fourthly, the winding gear space needs to be considered when winding, the distance between the iron yoke and the coil must be increased, and the casting needs to consider the space for mold assembly and disassembly. Fifth, after the transformer is manufactured, the coil cannot be disassembled (especially the casting coil), and the transformer has poor repairability.

The main advantages of the three-dimensional core resin cast transformer compared with stacked core resin cast dry type transformers are lower cost and better no-load characteristics, but it also has several 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, and the transformer is too high, which may lead to inconsistency with the height of the low-voltage cabinet when the cabinet is closed.

Transformer height is too high will also lead to the lack of height in the power distribution room, it is difficult to install and disassemble the electrical equipment. Second, the depth of the transformer cabinet increases.

Because the transformer cabinet is generally deeper than the low-voltage cabinet, the three-dimensional coil core transformer further widens the gap between the two, the distribution room design is more difficult to layout, and the space utilization is low.

Third, the three-dimensional coil core production plant has little market promotion for this product, and it must pay a certain price to obtain market recognition.

The relevant data are obtained by referring to the following data: The three-dimensional coil core fill factor can reach 0.95-0.96, which is about 3.5% to 5% larger than that of the laminated core, and the core utilization rate is about 4% higher than that of the laminated core, and the process coefficient after annealing can be reduced by about 15%. %, so that the weight of silicon steel can save about 10%, the winding needs to increase the distance between the coil and the iron yoke, resulting in about a 5% increase in the amount of silicon steel.

Based on the above factors, the same no-load characteristics of silicon steel can theoretically save about 12% in weight.

If the volume of the three-dimensional rolled core silicon steel is the same as that of the laminated iron core, the no-load characteristic can be improved by about 10%. However, it must be noted that the three-dimensional coil core needs annealing, considering the stability of the annealing process, it will also increase the cost of the core.

3, three-dimensional volume core resin cast dry-type transformer production key links

The main difference between a three-dimensional wound core transformer and a common stacked core transformer is that the core must be annealed after winding, and the core cannot be opened at the same time, and the iron core must be operated when winding and pouring. In summary, the main difficulties in the development and production of three-dimensional wound core transformers are:

First, the annealing process of the three-dimensional coil core. Due to different core structure sizes, the annealing process is also different. Even if the technology introduction includes these contents, our company needs to form its own annealing process according to the actual situation.

Secondly, the coil DFSDF must be wound on the iron core. If the windings are separated by high and low voltages, the coil fixing and mold loading and unloading are difficult. When Haihong transfers the mold technology during the transfer of technology, the key is how to improve the operating efficiency and effective protection during operation. .

If coils are integrally wound, new winding equipment needs to be developed. The use of open three-dimensional coiled iron cores can solve the above problems, but after Haihong's attempt to prove that its production efficiency has not been improved, it has caused the performance of the product to deteriorate significantly.

Third, the three coils are cast at the same time when pouring. Because the cutting end and large machining are not allowed, the final finishing and cleaning of the transformer is difficult. Fourth, once the product fails, the entire transformer may be scrapped because the resin casting coil cannot be disassembled.

4 Conclusion

The production of three-dimensional coil core transformers and our company's stacked core transformers now, in addition to winding and pouring have some similarities, the company also needs to introduce a full set of technology and provide an independent production site. From the technical difficulty point of view, it is mainly the process and tooling equipment assurance problem. As long as the process coefficient is determined in the design, the design is not difficult.

From the market point of view, the three-dimensional coil core has not yet become the mainstream product of distribution transformers.

With the gradual solution of the problems of amorphous alloy transformer materials, it has become the main force of energy-saving transformers. If the amorphous alloy transformer can solve the transformer's volume, magnetic properties and dynamic stability of the iron core, this transformer will also have a good market. prospect.

Although the three-dimensional coil core transformer has price and performance advantages in a certain capacity segment, its process and structural complexity, low production efficiency, technical deterrence and the company's current plant and equipment conditions are restricting the implementation of the project.

Iron core is a major concern for everyone. China Iron Core Trading Network is an e-commerce platform of China Netbank under the focus of iron core, which concentrates all the upstream and downstream enterprises of the country on genuine procurement and genuine wholesale. Provides professional core trading platforms and information for consumers and has abundant core resources. Fundamentally, the quality of the iron core can be guaranteed. So please pay attention to more core news, please come here! The above information is from China Iron Core Trading Network:/

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