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Characteristics and application of nanocrystalline iron core

Characteristics and application of nanocrystalline iron core


1、 Technical narration

Characteristics of high power (nano) transformer

High frequency variable frequency power supply The output power of the inverter welding machine is 20kHz ~ 50KHz. As the main transformer of the switching power supply, the traditional iron core raw material ferrite has low high frequency loss, However, the magnetic characteristics of its low frequency band (below 100kHz) are not good, and its magnetic induction value in saturated state (BS) is low, and the volume and net weight of the iron core are still large. In addition, the Curie temperature of ferrite is low, the heat resistance is poor, and the temperature is slightly higher, which leads to the reduction of BS value, easy saturation state and unstable operation state, so it is not suitable for application under high low-frequency power. Nanocrystalline raw materials have high-quality comprehensive magnetic energy, which is very suitable for variable-frequency power supply with high frequency power and reverse On the transformer welding machine. As the core of inverter transformer, it has been leading for a long time.

1、 Advantages of nanocrystals

Nanocrystalline raw materials also have the advantages of silicon steel sheet, permalloy and ferrite. Namely:

High magnetic induction: magnetic induction in saturated state BS = 1.2t, twice that of permalloy and 2.5 times that of ferrite. The power of iron core is large and can reach 15kw ~ 20kW / kg.

High permeability: original permeability of static data μ 0 can reach 120000 ~ 140000, which is very similar to permalloy. The permeability of the iron core of the transformer used to output power is more than 10 times that of ferrite, which greatly reduces the output power of excitation current and improves the high efficiency of the transformer.

Low loss: in the frequency range of 20kHz ~ 50KHz, it is 1 / 2 ~ 1 / 5 of ferrite to reduce the temperature rise of iron core.

High Curie temperature: the Curie temperature of nanocrystalline raw materials is 570 ℃, and the Curie temperature of ferrite is only 180 ℃ ~ 200 ℃.

Because of the above advantages, the transformer produced by nanocrystalline is used in variable frequency power supply On the inverter welding machine, the switching power supply Second, the credibility of the welding machine has been greatly improved:

Low loss and low temperature rise of transformer. The long-term specific application of many customers proves that the temperature rise of nanocrystalline transformer is far less than that of IGBT pipeline.

The iron core has high permeability, reduces the output power of excitation current, reduces copper loss and improves the high efficiency of transformer. The primary and intermediate inductors of the transformer are large, which reduces the impact of the current on the IGBT pipeline when the power supply is switched on and off.

In operation, the magnetic induction is high and the power is large, which can reach 15kw / kg. The volume of the iron core is reduced. It is a high-power variable-frequency power supply, which reduces the volume and expands the indoor space in the main engine box, which is beneficial to the heat discharge of IGBT pipeline.

The load working capacity of the transformer is strong, because the magnetic induction is selected around 40% of the magnetic induction in the saturated state. When the load is generated, it is only caused by the increase of magnetic induction

The IGBT pipeline is not easy to be damaged due to the saturation state of the iron core.

The Curie temperature of nanocrystalline raw materials is high. Assuming that the temperature is above 100 ℃, the ferrite transformer can no longer work, and the nanocrystalline transformer can completely work normally.

This advantage of nanocrystalline is understood and selected by more and more switching power supply manufacturers. A number of manufacturers in China have already selected nanocrystalline iron core and used it for many years. More and more manufacturers have just begun to apply or use. At this stage, it has been widely used in inverter welding machine, power supply system, electrolytic power supply for electroplating process, electromagnetic induction heating switching power supply, battery charging switching power supply and other industries, and will continue to be greatly improved in the next two years.

2、 There are many problems that everyone is concerned about

In the whole process of using nanocrystalline raw materials in variable frequency power supply, there have been some problems, such as noise problems, ductility problems, consistency problems, etc., which are harmful to the application and promotion to a certain extent. Now this problem has been gradually solved.

(1) Noise problem

There are various reasons for the generation of noise:

1. Due to the magnetostrictive index of raw materials, the magnetostrictive index of ferrite raw materials is relatively large. Although the ferrite transformer skeleton is solid core, sometimes there will be noise in application. The composition of nanocrystals is different and the magnetostrictive index is different. The composition applied in the previous two years is a universal aluminum alloy composition. Therefore, the noise problem of producing transformers is very obvious. With the deeper and deeper level of application, development and design, different aluminum alloy compositions are selected for different main purposes, To consider the special requirements of different components for magnetization. For example, as output power, output transformer, voltage transformer and common mode inductor, special components are developed and designed. The aluminum alloy composition adjusted according to the provisions of the output power transformer reduces the magnetostrictive index. It has been proved by customer application that the noise problem has been greatly improved.

2. The tightness of the iron core rewiring machine is greatly related to the quality of the applied amorphous strip. The specification error and uneven thickness of the amorphous strip lead to the loose iron core rewiring machine, which is very easy to cause noise. After adjusting the composition, the liquid steel has good fluidity, which is beneficial to the forming quality of amorphous strip. To a certain extent, it provides a beneficial guarantee for reducing the noise of iron core.

3. The problem at the rectifier circuit level is that the DC component in the power supply circuit is large, resulting in the increase of magnetic induction during the operation of the iron core and noise. Our experiments show that the noise increases with the increase of magnetic induction at work. Some manufacturers have adopted DC isolation measures in the power supply circuit, and there has been no noise problem in the application of nanocrystalline iron core for many years.

According to the above improvement, the noise problem is solved.

(2) Ductility problem

The key to the ductility of nanocrystalline iron core is reflected in the slag falling of iron core, which is a big problem for customers. It is not only a headache for simple installation, but also a potential safety hazard of short-circuit fault to the power circuit. After many years of practice and scientific research, the ductility problem has been greatly improved according to the adjustment of composition and processing technology. After adjusting the composition, the flexibility of amorphous strip is obviously improved. The thinning of amorphous strip also reduces the ductility. In addition, in the process of manufacturing iron core, the iron core is impregnated with non in-situ stress glue, which makes the iron core not fragile and completely eliminates the ductility problem of slag falling of the iron core. In addition, because the layer gap of the amorphous strip of the iron core is fixed by the non in-situ stress glue, it is not easy to cause co vibration and reduce the noise.

(3) Consistency challenges

Consistency is related to the production scale and the volume of production line equipment. In terms of the quality of amorphous strip, a 500kg production capacity machine and equipment are similar to 50kg production capacity machines and equipment. It is obvious that the consistency of composition and magnetic energy of the former commodity is better than that of the latter. Similarly, the quenching and tempering treatment in the processing process is the same. Therefore, large production scale and large volume of production line equipment are beneficial to consistency.

The consistency of nanocrystals in customer applications is reflected in the large dispersion of working voltage and inductor quantity in saturated state, sometimes more than twice the distance. The key reason is that the actual effect of electromagnetic field quenching and tempering treatment is poor, and there is no classification and selection in production, manufacturing and testing. With the adjustment of the composition of the output power transformer, it not only improves the ductility, but also reduces the residual magnetic induction compressive strength of the raw materials. Therefore, it expands the actual effect of electromagnetic field conditioning treatment, improves the saturated working voltage of the iron core, and plays a key role in the consistency of goods.

There is a gradual understanding of the whole process of the magnetic energy required by the variable frequency power supply. In the first two years, due to the small amount of use, we only pay attention to the loss and meet the requirements. Therefore, the characteristic detection only accurately measures the main parameter of loss. For special customers, increase the detection induced voltage value. With the increasing amount of application, a variety of provisions are clearly put forward, especially the provisions of characteristic consistency are very prominent. Because there is an understanding of the whole process of such regulations, there are some backwardness in terms of composition improvement, production and manufacturing institutions, testing specifications and so on. Therefore, it is harmful to the application and promotion. Today, this problem has been fully understood, and a variety of reasonable countermeasures have been adopted, and the consistency has been further improved.

(4) Price problem

The price problem is the most concern of customers, especially those who prepare the application in advance or just start the application. There is an immediate correlation between price and total output. In recent years, with

The application of nanocrystalline iron core is becoming more and more common. It is not only used for inverter welding machine, but also used in many industries such as electrolytic electroplating equipment, electromagnetic induction heating machine equipment, battery charging machine equipment, power supply system, UPS switching power supply, X-ray machine switching power supply, laser generator, DC variable frequency variable speed switching power supply, etc, The price has also been greatly reduced. At this stage, the price has been reduced by about 40% compared with the initial price. With the continuous expansion of transportation, the price will drop sharply, and the price of nanocrystals will be closer and closer to the price of ferrite.

At this stage, for the switching power supply with high power above 15kw, in fact, the price of nanocrystalline iron core is already lower than that of ferrite iron core. Due to the limited specification of ferrite iron core, the transformer skeleton necessary for high-power transformer is difficult to deal with. It is forced to apply many iron cores before the output power regulation can be considered. One nanocrystalline core is enough. In terms of price, ferrite is much more cost-effective, but the total price of many iron cores is higher than that of nanocrystalline iron cores.

3、 Commodity of nanocrystalline transformer

The applied nanocrystalline transformer is basically the coil inductance of the whole equipment manufacturer, because the design scheme of rectifier circuit of each manufacturer is different, the mastery of nanocrystalline raw materials is different, the mastery level of transformer production and processing technology is different, and the level of transformer produced is also different. Manufacturing high frequency transformer becomes a key step in manufacturing. Therefore, some manufacturers clearly put forward the regulation that whether the high-frequency transformer can be systematically produced and manufactured, and the whole equipment manufacturer should immediately purchase the transformer.

Ferrite is generally used as the transformer core for transformers in the frequency range of 20kHz ~ 50KHz,

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