Advantages and challenges of using nanocrystals in inverter power supplies

1. Advantages of Nanocrystals

 Nanocrystalline magnetic rings (ultramicrocrystalline iron cores) also have the advantages of silicon steel, permalloy, and ferrite cores. Right now:

 High magnetic induction: saturation state magnetic induction Bs=, which is twice that of permalloy. The transformer core has high power and can exceed 15 kW ~ 20 kW/kg.

 High magnetic permeability: The original magnetic permeability μ0 of static data can reach 120,000 to 140,000, which is very similar to that of permalloy. The magnetic permeability of the coil used to output power transformer is more than 10 times that of the ferrite core, which greatly reduces the excitation current output power and improves the efficiency of the transformer.

 Low loss: In the frequency range of 20kHz to 50kHz, the ferrite core is 1/2 to 1/5, reducing the transformer core temperature.

 High Curie temperature: The Curie temperature of the nanocrystalline magnetic ring (ultra-microcrystalline iron core) reaches 570°C, while the Curie temperature of the ferrite core is only 180°C ~ 200°C.

 Because of its advantages, nanocrystalline transformers are used in inverter power supplies, which has a great effect on improving the reliability of switching power supplies:

 The loss is small and the temperature of the transformer is low. The long-term practical use of many users has confirmed that the temperature of the nanocrystalline transformer is far lower than the temperature of the IGBT water pipe.

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

 During operation, the magnetic induction is high and the power is high, which can exceed 15Kw/kg. Reduce the volume of the transformer core. Especially for power inverters, the volume reduction increases the space inside the main chassis, which is beneficial to the heat dissipation of the IGBT water pipe.

 The load capacity of the transformer is strong, because the magnetic induction during operation is selected to be around 40% of the saturation induction. When the load occurs, it is only due to the increase in magnetic induction that it will become hot, and it will not damage the IGBT due to the saturation of the transformer core. water pipe.

 The Curie temperature of the nanocrystalline magnetic ring (ultra-microcrystalline iron core) is high. If the temperature exceeds about 100°C, the ferrite core transformer will no longer be able to work, but the nanocrystalline transformer can work normally.

 This advantage of nanocrystals has been understood and adopted by more and more switching power supply manufacturers. A group of manufacturers in China have already adopted nanocrystalline transformer cores and have used them for many years. More and more manufacturers are beginning to use or use it. At present, it has been widely used in inverter welding machines, power systems, electrolytic power supplies for electroplating processes, induction heating equipment, charging power supplies and other industries, and there will be even greater improvements in the next two years.

 2. Issues that everyone is concerned about

 In the process of using nanocrystalline magnetic rings (ultramicrocrystalline cores) in inverter power supplies, there have been some problems such as noise problems, ductility problems, consistency problems, etc., which have affected the application promotion to a certain extent and caused care. Now these problems have been gradually solved.

(1) Noise problem

 Noise is generated for various reasons:

 1. Due to the magnetostrictive index of the material itself, the magnetostrictive index of the ferrite core material is relatively large. Although the ferrite core is solid, noise sometimes occurs during use. The composition of nanocrystals is different, and the magnetostrictive index is different. The composition used in the past two years is a general aluminum alloy composition. Therefore, the noise problem in the production of transformers is very obvious, and the application, development and design More and more, different alloy compositions are used for different purposes to meet the magnetic requirements of different components. For example, special components have been developed and designed for power transformers, voltage transformers, common mode inductors, etc. The alloy composition adjusted according to the requirements of the power transformer reduces the magnetostrictive index. It has been confirmed by user applications that the noise problem has been greatly improved.

 2. The reason why the transformer core is wound tightly is closely related to the quality of the amorphous strip used. The size error and uneven thickness of the amorphous strip can cause the transformer core to be wound too loosely, which can easily cause noise. . After adjusting the composition, the molten steel has good fluidity, which is beneficial to the forming quality of the amorphous strip. It provides a beneficial guarantee for reducing the noise of the transformer core to a certain extent.

 3． The problem at the rectifier circuit level is that the DC component in the power circuit is large, which causes the magnetic induction of the transformer core to increase, causing noise. Our experiments have confirmed that the noise increases as the magnetic induction increases during work. Some manufacturers have adopted DC isolation measures in power circuits and have used nanocrystalline transformer cores without any noise problems for many years.

 Through the improvement of left and right, the noise problem has been basically solved.

(2) Ductility problem

 The ductility of the nanocrystalline transformer core is mainly reflected in the slag shedding of the transformer core, which is a major problem for users. It is not only a headache for simple installation, but also easily causes short-circuit faults in the power circuit and safety hazards. After many years of practice and research, the ductility problem has been greatly improved through adjustments to ingredients and processing techniques. After the composition is adjusted, the flexibility of the amorphous strip is significantly improved. Thinning of the amorphous ribbon also reduces ductility. In addition, in the process of manufacturing the transformer core, the transformer core is impregnated with non-stress adhesive, which makes the transformer core less fragile and completely eliminates the ductility problem of slagging in the transformer core. At the same time, because the stress-free glue fixes the gaps between the amorphous strips of the transformer core, it is less likely to cause resonance and reduces the generation of noise.

 (3) Consistency issues

 Consistency is related to the scale of manufacturing operations and the volume of production line equipment. Judging from the quality of amorphous strips, a 500KG production capacity machine is comparable to a 50KG production capacity machine. The same can produce 500KG amorphous strips. Obviously, the former product has better consistency in composition and magnetic energy. The latter one. The conditioning and tempering treatments during processing are the same. Therefore, large-scale manufacturing operations and large production line equipment are beneficial to consistency.

 The consistency of nanocrystals in customer applications is manifested in the large discreteness of the saturation state operating voltage and inductor quantity, sometimes more than double the distance. The main reason is that the effect of electromagnetic field quenching and tempering treatment is poor and there is no classification and selection in manufacturing inspection. The subsequent adjustment of the components used in the power transformer not only improves the ductility, but also reduces the residual magnetic intensity of the material, thus increasing the effect of electromagnetic field quenching and tempering and increasing the saturation voltage of the transformer core. , plays an important role in product consistency.

 3. Nanocrystalline transformer products

 The nanocrystalline transformers used are almost all wound by the equipment manufacturer itself, because each factory has different designs of rectifier circuits, different understanding of nanocrystalline magnetic rings (ultra-microcrystalline iron cores), and different requirements for transformers. The level of mastery of electrical appliance manufacturing and processing technology is different, and the level of produced transformers is also different. Manufacturing high-frequency transformers has become an important step in manufacturing. Therefore, some manufacturers have raised the possibility of systematic production of high-frequency transformers and the requirement for all equipment manufacturers to directly purchase transformers.

 Originally, transformers in the frequency range of 20kHz to 50kHz generally used ferrite cores as transformer coils. The most common forms of transformer cores were U-type or EI-type. O-type transformer cores, U-type or EI-type transformer cores were rarely used. There is no structural way to reduce the leakage inductance of the transformer.

 Due to the advantages of nanocrystalline magnetic rings (ultra-microcrystalline iron core), it provides ideal materials for the practicality and efficiency of high-frequency transformers. New materials promote the advent of a new construction of high-frequency transformers.

 This kind of patented transformer named "Beetle" was later improved by others and called "H" type transformer, which was also patented. These two transformers make full use of nanocrystalline magnetic rings (ultra-microcrystalline). The magnetic characteristics of high magnetic permeability, high magnetic induction intensity, low loss and small magnetic leakage of the toroidal transformer core have broken new ground in the primary and secondary structures of the transformer. The metal protection box of the transformer core is used as the secondary coil of the transformer, which is suitable for large current output. The primary coil is evenly wound around the secondary side, and the leakage inductance is not large. The fixed support point of the transformer is integrated with the bus output, which is beneficial to heat dissipation.

 The advantages of this type of transformer are:

 1. Large output power: 10 kW～20kW, power can exceed 15 kW～20kW/kg

 2. Leakage inductance is small, generally less than 5μH, preferably less than 2μH

 3． High efficiency, over 99%

 4. Light weight, the net weight of the 15 kW transformer is 3KG, and the volume is 160×150×95 mm

 5. The appearance design is beautiful and elegant.

 The practical application of nanocrystalline transformers effectively utilizes the characteristics of nanocrystalline soft magnetic materials; it is beneficial to the practicality and standardization of high-voltage power transformers; it is beneficial to the improvement of high efficiency and level of transformers; it is beneficial to inverter welding machines, Electroplating process, electrolysis and other machinery and equipment

 Productivity improvements. Currently, there are many manufacturers that can produce this type of transformer.

 Nowadays, some entire equipment manufacturing has begun to use "Ω" type transformers to achieve integrated manufacturing. This is a "more, faster, better, and more economical" approach.

 4. Conclusion

 Due to their excellent characteristics, amorphous and nanocrystalline soft magnetic materials make up for the shortage of silicon steel and ferrite core materials in different applications, bringing various electronic devices to a new level, improving efficiency, Significant environmental protection and energy saving effects have been achieved. New materials show vigorous vitality.

 Nowadays, more and more people know about amorphous magnetic cores and nanocrystalline magnetic rings (ultramicrocrystalline iron cores). In addition to transformers, amorphous magnetic cores and nanocrystalline magnetic rings (ultramicrocrystalline iron cores) can As the transformer core material for voltage transformers, series reactors, controllers, filters and other components, its application scope also involves electrical products in people's daily lives, smart meters, DC variable frequency air conditioners, leakage protection circuit breakers, etc. Transformation measurement, power distribution equipment, telemetry sensing technology of power supply system, electric locomotive central air conditioner of railway line system, inverter power supply of electric locomotive, railway signal sensing technology, etc., are also used in aerospace, aviation It has been selected and finalized in various military and national new technology projects such as companies and ships.