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The characteristics and advantages of ultra-microcrystalline iron core

The characteristics and advantages of ultra-microcrystalline iron core

2021-09-28

1. Technical narrative


Powerful (nano) transformer characteristics


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 material ferrite has low high frequency loss, but its low frequency range (below 100kHz) The magnetic characteristics of) are not very good, and the magnetic induction value (Bs) in its saturation state is low, and the volume and net weight of the iron core are still large. In addition, the Curie temperature of ferrite is low, and the heat resistance is poor. A slightly higher value will cause the Bs value to decrease, easy to saturate, and unstable operation, which is not suitable for applications with high low-frequency power. Nanocrystalline raw materials, with high-quality comprehensive magnetic energy, are very used in high-frequency and high-power variable-frequency power supplies and inverter welding machines. As the iron core of the inverter power transformer, it has been a long-term leader.


2.Advantages of Nanocrystalline (Nanocrystalline Iron Core Company)


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


High magnetic induction: the saturation magnetic induction Bs=1.2T, which is twice that of permalloy and 2.5 times that of ferrite. The power of the iron core is large, capable of 15kW~20kW/kg.


High permeability: The original permeability μ0 of static data can reach 120,000 to 140,000, which is very similar to Permalloy. The magnetic permeability of the transformer core used to output power is ten times that of ferrite, which greatly reduces the output power of the excitation current and improves the high efficiency of the transformer.


Low loss: In the frequency range of 20kHz~50kHz, ferrite is 1/2~1/5, which reduces the temperature rise of the iron core.


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


Because of the above advantages, the transformer manufactured by nanocrystalline is used in variable frequency power supply and inverter welding machine, which has greatly improved the credibility of switching power supply and second protection welding machine:


The loss is small and the transformer temperature rise is low. Many customers' long-term specific applications have confirmed that the temperature rise of the nanocrystalline transformer is much smaller than the temperature rise of the IGBT pipeline.


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


High magnetic induction and high power during work can achieve 15Kw/kg. Reduce the volume of the iron core. It is a high-power variable frequency power supply. The reduction in volume promotes the expansion of the indoor space in the main box, which is beneficial to the heat removal of the IGBT pipe.


The load capacity of the transformer is strong, because the magnetic induction is selected to be around 40% of the magnetic induction in the saturation state during work. When the load is generated, the magnetic induction is only caused by the increase


It is not easy to destroy the IGBT pipe due to the saturation of the iron core.


The Curie temperature of the nanocrystalline raw material is high. When the temperature is assumed to be above 100°C, the ferrite transformer can no longer work, and the nanocrystalline transformer can completely work normally.


This advantage of nanocrystalline has been understood and selected by more and more switching power supply manufacturers. A group of Chinese manufacturers have already selected nanocrystalline iron cores and used them for many years. More and more manufacturers have just started to apply or use. At this stage, it has been widely used in industries such as 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 have more substantial improvements in the next two years.


2. There are many problems that everyone is concerned about


In the whole process of applying nanocrystalline raw materials to variable frequency power supplies, there have been some problems such as noise problems, ductility problems, consistency problems, etc., which harmed the application and promotion to a certain level and caused concern. Now this kind of problem has been gradually dealt with.


(1) Noise problems


There are various reasons for noise:


1.Due to the magnetostriction index of the raw material itself, the magnetostriction index of the ferrite raw material is relatively large, although the ferrite transformer skeleton is solid core, noise sometimes occurs in the application. The composition of nanocrystals is different, and the magnetostriction index is different. The composition used in the first two years is a universal aluminum alloy composition. Therefore, the noise problem in the production of transformers is very obvious. Going deeper and deeper, choose different aluminum alloy components for different main purposes to consider the special requirements of different components for magnetization. For example, as output power output transformers, voltage transformers, common mode inductors, etc., special components have been developed and designed. The aluminum alloy composition adjusted in accordance with the regulations of the output power transformer reduces the magnetostriction index. The customer's application has confirmed that the noise problem has been greatly improved.


2. Due to the tightness of the iron core rewinding machine, it is very related to the quality of the applied amorphous strip. The specification error and uneven thickness of the amorphous strip all cause the iron core rewinding machine to be too loose, 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 the amorphous strip. To a certain level, it is beneficial to reduce the noise of the iron core.


3. The problem at the rectifier circuit level is that the DC component in the power circuit is large, which leads to an increase in the magnetic inductance during the operation of the iron core and causes noise. Everyone’s experiments have confirmed that the noise increases with the increase of the magnetic induction during work. Some manufacturers have adopted direct current isolation countermeasures on the power supply circuit, and the application of nanocrystalline iron cores has not caused noise problems for many years.


According to the above improvement, the foundation of the noise problem has been dealt with.


(2) The ductility problem


The key to the ductility of the nanocrystalline iron core is reflected in the slag drop of the iron core, which is a big problem for customers. It is not only a headache for simple installation, but also very easy to cause short-circuit failure to the power circuit. After many years of practical activities and scientific research, the ductility problem has been greatly improved based on the adjustment of the composition and processing technology. After the composition is adjusted, the flexibility of the amorphous ribbon is significantly improved. The thinning of the thickness of the amorphous strip also reduces the ductility. In addition, in the process of manufacturing the iron core, the iron core is impregnated with non-earth-stress glue to make the iron core not fragile and completely eliminate the problem of the ductility of iron core slag drop. In addition, because the non-ground stress glue fixes the interlayer gap of the iron core amorphous strip, it is not easy to cause resonance and reduces the noise.


(3) Consistency problem


Consistency is related to the scale of production and the volume of production line equipment. From the perspective of the quality of amorphous strips, a 500Kg production volume of machinery and equipment is comparable to a 50kg production volume of machinery and equipment. The same production of 500Kg amorphous strips is obvious. The former product has better consistency in composition and magnetic energy. For the latter. The same is true for the quenching and tempering treatment in the processing process. Therefore, large production scale and large production line equipment volume are beneficial to consistency.


In customer applications, the consistency of nanocrystals is specifically manifested in the large dispersion of the saturated operating voltage and the amount of inductors, sometimes more than twice the distance. The key reason is that the actual effect of the electromagnetic field quenching and tempering treatment is poor, and the manufacturing inspection is not classified and selected. Accompanied by the adjustment of the components used to output the power transformer, not only the ductility is improved, but also the residual magnetic induction compressive strength of the raw materials is reduced. Therefore, the actual effect of the electromagnetic field quenching and tempering treatment is expanded, and the saturation working voltage of the iron core is increased. It plays a key role in product consistency.


There is a gradual understanding of the whole process of the magnetic energy stipulated by the variable frequency power supply. In the first two years, because the amount of use is small, it is enough to pay attention to the consumption and comply with the regulations. Therefore, the characteristic test only accurately measures the main parameter of loss. For special customers, increase the detection induced voltage value. With the increasing amount of applications, various regulations have been clearly proposed, and the regulations on the consistency of characteristics are very prominent. Because there is an understanding of the whole process of such regulations, no matter in terms of composition improvement, manufacturing organization, testing specifications, etc., they are a little behind. Therefore, it is harmful to application promotion. Now that this issue has been fully understood, a variety of reasonable countermeasures have been adopted, and the consistency has been further improved.


(4) Price problem


The price problem is what customers are most concerned about. It is very important for customers who have prepared applications in advance or have just started applications. The price is immediately related to the total output. In recent years, as the industries using nanocrystalline iron cores have become more and more common, they are used not only for inverter welding machines, but also for electrolytic plating equipment, electromagnetic induction heating equipment, and batteries. In industries such as charging equipment, power supply systems, UPS switching power supplies, X-ray machine switching power supplies, laser generators, DC variable-speed switching power supplies, etc., the production volume is increasing, and the price is also greatly reduced. The price comparison at this stage is the most The initial price has already been reduced by about 40%. With the continued expansion of usage, the price will drop sharply, and the price of nanocrystals will become closer to the price of ferrite.


For the switching power supply with high power above 15KW at this stage, the price of nanocrystalline iron core is already lower than that of ferrite iron core. Due to the limited specifications of ferrite cores, it is difficult to handle the transformer skeleton necessary for high-power transformers, and it is necessary to apply multiple cores before considering the output power regulations. One nanocrystalline iron core is sufficient. From the price point of view, ferrite is much more cost-effective, but the total price of many iron cores is higher than the price of nanocrystalline iron cores.


3. Commodities of nanocrystalline transformers


The nanocrystalline transformers used are basically the coil inductance of the entire equipment manufacturer itself, because each manufacturer has different design schemes for the rectifier circuit, different mastery of nanocrystalline raw materials, and different levels of mastery of the transformer manufacturing process. Similarly, the level of transformers manufactured is not the same. Manufacturing high-frequency transformers has become a key step in manufacturing. Therefore, some manufacturers have clearly stated that whether high-frequency transformers can be manufactured systematically and the entire equipment manufacturers should purchase transformers immediately.


In the original transformers in the frequency range of 20kHz to 50kHz, ferrite is generally used as the transformer core.


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