Nanocrystalline materials for new energy vehicle products
1. What are the current applications of nanocrystalline materials in new energy vehicles? What are their advantages over other soft magnetic materials?
At present, the main markets for magnetic components of nanocrystalline soft magnetic materials for vehicle applications include electric vehicle on-board chargers, on-board inverters, motor bearing protection, and electric vehicle charging stations. There are many application methods, including inductors, chokes, CTs, and magnetic rings. I summarize the advantages of nanocrystalline magnetic rings into several keywords: compact, efficient, and stable. Compact refers to the high saturation magnetic density of nanocrystalline materials, which are smaller in size than other soft magnetic materials with the same performance. Efficient refers to the high magnetic permeability, low loss, and better electromagnetic interference suppression effect of nanocrystalline materials; stable refers to the high Curie temperature, low temperature coefficient, and stronger reliability of nanocrystalline materials.
2. What technical requirements are put forward for nanocrystalline materials under the trend of 800V electric drive system?
In the current soft magnetic material system, it is generally believed that the higher the magnetic permeability of the material, the worse its anti-saturation characteristics. However, there are some scenarios in vehicle applications, such as three-phase common-mode inductors in high-power OBC modules and nanocrystalline filter magnetic rings used in electric drives, which will have unbalanced currents, causing high-permeability nanocrystalline magnetic rings to enter a saturated state, causing heating and even burning. Therefore, how to reduce the magnetic permeability characteristics of nanocrystalline magnetic rings in high-current applications to improve their anti-saturation characteristics has become a technical difficulty in the nanocrystalline industry.
For example, the low-voltage side power inductors in DC-DC modules generally used low-permeability nickel-zinc ferrites, but now the power of DC-DC modules has been increasing, and the anti-saturation characteristics of nickel-zinc ferrites are not enough. As one of the technology leaders in domestic low magnetic permeability nanocrystal solutions, we have achieved mass production of ultra-low magnetic permeability nanocrystalline magnetic rings with μ=150. The ultra-low magnetic permeability nanocrystals can reach 1.4T (Tesla), which is significantly better than the 0.5T (Tesla) of nickel-zinc ferrite.
3. Nowadays, traditional circular nanocrystalline materials are rarely used in vehicle designs. In order to meet the space requirements of the design, what new design structures and new production processes have your company adopted?
Nanocrystalline is wound by strips, so it is sensitive to stress. In order to maintain stable performance, stress needs to be reduced as much as possible during the manufacturing process. The ring is the least stressed during the manufacturing process, followed by the runway shape, and finally the rectangle. Therefore, there are more rings in traditional applications.
However, despite the superior performance of the ring, it is not very commonly used in the automotive industry due to its insufficient space utilization. The runway shape is now more widely used because it performs better in a small space, followed by the rectangle. C-cut magnetic rings are also used in some high-power scenarios. Since these shapes are formed by ring deformation, how to eliminate the stress influence of the magnetic ring while maintaining the shape and maintaining the stability of the magnetic ring is the main problem. Through several years of experiments and precipitation, we have optimized the curing formula, which has less performance attenuation than the traditional curing process; at the same time, through a more optimized strong magnetic field heat treatment process, the magnetic ring itself has stronger stress resistance.
At the same time, for special-shaped iron cores, we can also use stacking and punching methods to process them, which greatly increases the application scenarios of nanocrystalline materials.
4. What do you think is the future research direction of nanocrystals?
Traditional nanocrystals are generally designed for 10K-100K frequencies, but now the high-order harmonic interference in motor controller modules is becoming more and more high-frequency, which means that nanocrystal filter magnetic rings must have better high-frequency impedance and a wider frequency range to meet EMC requirements. Therefore, high impedance at high frequencies, better anti-saturation ability, and stability under high and low temperatures and stress conditions are still our main research goals in the future.
