Application of Nanocrystalline High Frequency Transformer on Inverter Power Supply
Application of Nanocrystalline High Frequency Transformer on Inverter Power Supply
The operating frequency of the high-frequency inverter power supply is around 20 kHz to 50 kHz. As the main transformer of the power supply core, the traditional core ferrite has lower high frequency loss, but its lower frequency band (below 100 kHz) has less magnetic properties. Well, because its saturation magnetic induction value (Bs) is low, the volume and weight of the core are still large. In addition, the Curie temperature of the ferrite is low, the thermal stability is poor, and the temperature is slightly higher, which causes the Bs value to decrease and is easy to be saturated. The working condition is unstable and is not suitable for use under high frequency and high power. Nanocrystalline high-frequency transformer has excellent comprehensive magnetic performance, especially applied to high-frequency high-power inverter power supply. As the core of inverter transformer, it has shown certain advantages.
Applications: High-power switching power supply main transformer (such as inverter welding machine power supply, X-ray power supply, laser power supply, communication equipment power supply, high-frequency induction heating power supply, UPS)
Performance characteristics: high saturation magnetic induction, high magnetic permeability, high Curie temperature, low loss. The saturation magnetic induction is three times that of ferrite. The same volume of iron core is twice as large as the ferrite output power, and it has greater overload resistance. The core loss in the frequency range of 20 kHz to 50 kHz is 1/2 to 1/5 of the ferrite loss. The magnetic permeability is 10 times or more that of the ferrite, so the excitation power is small, and thus the copper loss is also reduced. The Curie temperature is 570oC, which is three times that of ferrite.
Nanocrystalline material High frequency transformer (inverter welding machine Power Transformer)
1. Advantages of nanocrystalline materials
The nanocrystalline high-frequency transformer has the advantages of silicon steel, permalloy and ferrite.
High magnetic induction: The saturation magnetic induction Bs=1.2T, which is twice that of permalloy and 2.5 times that of ferrite. The core has a high power density and can reach 15-20 kW/kg;
High magnetic permeability: static initial magnetic permeability μ0 can be as high as 12 to 140,000, which is equivalent to permalloy. The magnetic permeability of the core of the power transformer is more than 10 times that of the ferrite, which greatly reduces the excitation power and improves the efficiency of the transformer;
Low loss: ferrite 1/2 to 1/5 in the frequency range of 20 kHz to 50 kHz, reducing the temperature rise of the core;
The Curie temperature is high: the Curie temperature of the high-frequency transformer of nanocrystalline material reaches 570 °C, and the Curie temperature of ferrite is only 180~200 °C.
Due to the above advantages, the transformer made of nanocrystalline material is applied to the inverter power supply, which plays an obvious role in improving the reliability of the power supply:
The loss is small, the temperature rise of the transformer is low, and the long-term practical use of a large number of users proves that the temperature rise of the nanocrystalline material transformer is far lower than the temperature rise of the IGBT tube;
The core has high magnetic permeability, reduces the excitation power, reduces the copper loss, and improves the efficiency of the transformer. The primary inductance of the transformer is large, which reduces the impact of the current on the IGBT tube during switching;
The working magnetic induction is high and the power density is large, which can reach 15kW/kg or more. Reduce the volume of the core. In particular, the high-power inverter power supply has a smaller volume, which increases the space inside the chassis, which is beneficial to the heat dissipation of the IGBT tube;
The overload capability of the transformer is strong. Since the working magnetic induction is selected to be about 40% of the saturation magnetic induction, when the overload occurs, the heat is generated only due to the increase of the magnetic induction, and the IGBT tube is not damaged due to the saturation of the core;
The high temperature transformer of nanocrystalline material has a high Curie temperature. Assuming that the temperature reaches 100 °C or above, the ferrite transformer can no longer work, and the nanocrystalline transformer can work normally.
These advantages of nanocrystalline materials have been recognized and adopted by more and more power supply manufacturers. A number of domestic production plants have adopted nanocrystalline iron cores and have been used for many years. At present, it has been widely used in inverter welding machines, communication power supplies, electroplating electrolysis power supplies, induction heating power supplies, charging power supplies, etc., and there will be more applications in the next few years.
2some issues that everyone cares about
In the process of applying high-frequency transformers of nanocrystalline materials to inverter power supplies, some problems such as noise, brittleness, and consistency have appeared, which have affected the promotion and application to a certain extent, causing concern. Now these problems have been gradually solved.
2.1 noise problem
There are many reasons for the formation of noise: (1) The magnetostriction coefficient of the material itself, the core expansion coefficient of the ferrite material is relatively large, although the ferrite core is solid, noise sometimes occurs in use. The composition of nanocrystalline materials is different, the magnetostriction coefficient is different, and the components used in previous years are a common alloy component. Therefore, the noise problem of manufacturing transformers is more prominent, and as applications and developments become more and more in-depth, Different alloy compositions are used for different applications to meet the special magnetic requirements of different devices. For example, as a power output transformer, a current transformer, a common mode inductor, etc., special components have been developed. According to the requirements of the power transformer, the composition of the alloy is reduced, and the magnetostriction coefficient is reduced. The noise problem has been greatly improved by the use of the user; (2) the reason why the core is wound tightly, which has a great relationship with the quality of the strip used. The deviation of the strip size and the uneven thickness will cause the core to be wound tightly and cause noise. After adjusting the composition, the molten steel has good fluidity, which is beneficial to the forming quality of the strip, and provides a favorable guarantee for reducing the core noise to a certain extent; (3) the problem of the inverter circuit, the DC component in the circuit is large, causing the work of the core The magnetic induction is increased, causing noise. Our experiments show that the noise increases with the increase of the working magnetic induction. Some manufacturers have adopted DC-blocking measures on the circuit, and there has been no noise problem for many years using nanocrystalline iron cores.
Through the above improvements, the noise problem has basically been solved.
2.2 Brittleness problem
The brittleness of the nanocrystalline core mainly reacts to the iron core slag, which is the biggest problem reflected by the user. It is not only a headache for the installation operation, but also a hidden danger of short circuit to the circuit. After years of practice and research, the brittleness problem has been greatly improved through the adjustment of components and processes. After the composition is adjusted, the flexibility of the strip is significantly improved. The thinning of the strip thickness also reduces the brittleness. In addition, in the process of manufacturing the core, the core is impregnated with no stress glue, so that the core is not easily broken, and the brittleness problem of the core slag is completely solved. At the same time, since the stress-free glue fixes the layer gap of the core strip, it is less prone to resonance and reduces the generation of noise.
2.3 consistency issues
Consistency is related to the scale of production and to the capacity of the production equipment. From the quality of the strip, a 500 kg output device and a 50 kg output device are similarly produced, and the same 500 kg strip is produced. Obviously, the former has better consistency in composition and magnetic properties than the latter. The same is true for heat treatment in the production process. Therefore, the large scale of production and the large capacity of production equipment are favorable for consistency.
In the user's use, the consistency of the high-frequency transformer of nanocrystalline material is mainly manifested in the large dispersion of saturation voltage and inductance, sometimes more than doubled. The main reason is that the effect of magnetic field heat treatment is poor, and the production inspection is not classified and screened. As the composition of the power transformer is adjusted, not only the brittleness is improved, but also the residual magnetic induction strength of the material is reduced. Therefore, the effect of the magnetic field heat treatment is increased, and the saturation voltage of the core is increased, which plays an important role in product consistency.
There is a gradual understanding of the magnetic properties required for the inverter power supply. In the past few years, due to the small amount of usage, only the loss is required to meet the requirements. Therefore, the performance test only measures the loss parameter. Increase the test induced voltage value for a specific user. As the volume of applications increases, so does the various requirements, especially the requirement for performance consistency. Due to the understanding of this requirement, there are some lags in terms of composition improvement, production organization, and testing standards. Therefore, it has a certain impact on the promotion and application. Now that this issue has been sufficiently recognized and a variety of effective measures have been taken, the consistency has been greatly improved.
2.4 price problem
Price issues are of the utmost concern to users, especially those who are ready to use or just starting to use. The price has a direct relationship with the production volume. In recent years, with the increasing application of nanocrystalline iron core high-frequency transformers, not only for inverter welding machines, but also for electrolytic plating equipment, induction heating equipment, charging equipment. In the fields of communication power supply, UPS power supply, X-ray power supply, laser power supply, and variable frequency speed control power supply, the output is getting larger and larger, and the price is also greatly reduced. The current price has dropped by about 40% compared with the original price. As the amount of application continues to increase, the price will become lower and lower, and the price of nanocrystalline materials will be closer to the price of ferrite.
At present, for a high-power power supply of 15 kW or more, because the size of the ferrite core is limited, the core required for the high-power transformer is difficult to solve, and several cores have to be used to meet the power requirement. And a nanocrystalline heart can be used. From the perspective of unit price, ferrite is much cheaper, but the total price of several cores is higher than the price of nanocrystalline core.
3 nano crystal transformer products
Due to the different design of inverter circuits in different factories, different understanding of nanocrystalline materials, and different degrees of mastery of transformer manufacturing processes, the level of transformers manufactured is also different. The manufacture of high frequency transformers has become an important part of production. Therefore, some manufacturers have suggested that it is possible to specialize in the production of high-frequency transformers, and the whole machine manufacturer directly purchases the requirements of the transformer.
The original transformers in the frequency range of 20 kHz to 50 kHz generally use ferrite as the transformer core. The iron cores are mostly U-shaped or EI-type. A few use O-shaped cores. U-shaped or EI-type iron cores are difficult to reduce the leakage inductance of the transformer. .
The advantages of nanocrystalline high frequency transformers are:
High power: 10~20kW, power density can reach 15~20kW/kg;
The leakage inductance is small, generally less than 5μH, preferably less than 2μH; the efficiency is high, reaching more than 99%; the volume is small and the weight is light, the weight of the 15 kW transformer is 3kg, the volume is 160mm×150mm×95mm; the appearance is beautiful.
Due to the structure and processing of such high-frequency transformers, the price is relatively high, and currently only a certain number of applications have been obtained on electroplating and electrolysis power sources. There are still difficulties in promoting the industry with fierce price competition.
The productization of nanocrystalline transformers makes reasonable use of the properties of nanocrystalline soft magnetic materials; it is beneficial to the improvement of transformer efficiency and level; it is beneficial to the improvement of production efficiency of inverter welding machine, electroplating and electrolysis. Several manufacturers are currently able to produce such transformers.
Prospect of 4 amorphous and nanocrystalline soft magnetic materials
Amorphous and nanocrystalline high-frequency transformers make up for the shortage of silicon steel and ferrite materials in different applications due to its excellent characteristics, which has improved various electronic products to a new level, improved efficiency, and achieved remarkable results. energy saving effect. The new material shows a vibrant vitality.
The scope of application also includes: household appliances, smart meters, DC inverter air conditioners, leakage protection switches, etc. in daily life; power transmission and transformation measurement, power distribution, telemetry and sensing, etc.; locomotive air conditioning and electric locomotive of railway system Inverter power supply, railway signal sensing, etc. It is also used in aerospace, aviation, marine and other military and national high-tech projects.
High efficiency, energy saving and high performance-price ratio are the goals pursued by each product. Nanocrystalline high-frequency transformers provide an ideal choice for inverter power supply. To promote the development of inverter power supply in China, we will provide excellent services.