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In the application of nanocrystalline toroidal cores (ultra-microcrystalline iron cores) in inverter power supplies, certain problems including noise, brittleness and inconsistent performance once emerged, hindering their popularization and application to a certain extent and attracting widespread attention. These issues have been gradually resolved at present.

(I) Noise Issue

Noise originates from multiple causes:

Magnetostriction coefficient of the raw material itself: Ferrite materials feature relatively high magnetostriction coefficients; even solid ferrite cores may generate noise during operation. Nanocrystalline materials deliver varying magnetostriction coefficients subject to different alloy compositions. Early adopted general-purpose alloy formulations led to prominent noise in finished transformers. With in-depth research and application development, customized alloy compositions have been developed for different scenarios to meet the special magnetic requirements of various components. For instance, dedicated formulations have been developed for power output transformers, current transformers, nanocrystalline toroidal common-mode inductors, etc. Alloy compositions optimized for power transformers effectively reduce the magnetostriction coefficient, and practical application by customers verifies that noise has been greatly mitigated.

Tightness of core winding: This is highly correlated with the quality of strip raw material. Dimensional tolerance and uneven thickness of strips will result in loose winding of cores and consequent noise. Optimized compositions improve the fluidity of molten steel, promoting better forming quality of strips, which lays a solid foundation for core noise reduction.

Defects in inverter circuit design: Excessive DC component in the circuit elevates the operating magnetic flux density of the core and triggers noise. Our experiments prove that noise intensifies as operating magnetic flux density rises. Some manufacturers adopt DC-blocking circuit designs, achieving noise-free operation of nanocrystalline cores for years.

Thanks to the above optimizations, the noise problem has been basically solved.

(II) Brittleness Issue

The most prominent customer complaint regarding nanocrystalline cores is brittleness manifested as core chipping. It not only complicates assembly operation but also poses hidden short-circuit risks to circuits. After years of research and trials, brittleness has been substantially improved via composition adjustment and process optimization. Modified formulations greatly enhance the flexibility of strips, and thinner strip thickness further reduces brittleness. In addition, a stress-free adhesive impregnation process is adopted in core production to prevent fragmentation, thoroughly solving the chipping problem caused by brittleness. Meanwhile, the stress-free adhesive fixes interlayer gaps between strip layers, restraining resonance and further suppressing noise generation.

(III) Consistency Issue

Product consistency is associated with production scale and equipment capacity. In terms of strip quality, to produce 500 kg of strip material, equipment with a 500 kg single-batch capacity delivers far better consistency in composition and magnetic properties than 50 kg-batch equipment. The same rule applies to the heat treatment process during production. Larger production scales and higher-capacity equipment are conducive to improved consistency.

In actual customer application, poor consistency of nanocrystalline cores is mainly reflected in large dispersion of saturation voltage and inductance, with values sometimes differing by more than double. Root causes include insufficient effect of magnetic field heat treatment and lack of classification & screening in incoming inspection. Composition modification for power transformer applications not only improves brittleness but also lowers residual magnetic flux density of the material, strengthening the effect of magnetic field heat treatment, boosting core saturation voltage, and playing a vital role in improving product consistency.

The industry has gone through a gradual cognition process regarding magnetic property requirements of nanocrystalline cores  inverter power supplies . In early years with low consumption volume, only core loss was required to meet the standard, hence only core loss was tested in routine inspection; individual customers additionally required induction voltage testing. Growing market demand has raised diversified requirements, among which consistency stands out as a critical indicator. Due to the lagging cognition of this demand, upgrades in composition modification, production arrangement and testing standards fell behind market needs, restricting product promotion. At present, sufficient attention has been paid to this problem, and multiple effective measures have been implemented to greatly improve product consistency.

(IV) Price Issue

Price is the top concern for customers, especially those preparing to adopt or newly adopting nanocrystalline products. Product price is directly linked to production volume. In recent years, expanding application scenarios have driven mass adoption of nanocrystalline iron cores, which are widely used not only in inverter welding machines, but also in industrial Inductor nanocrystalline core transformers, electroplating & electrolysis equipment, induction heating equipment, battery chargers, communication power supplies, UPS systems, X-ray power supplies, laser power supplies, variable-frequency speed regulation power supplies and other fields. Expanded output has brought a substantial price cut, with current prices around 40% lower than the initial launch price. Continuous volume growth will further drive prices down, narrowing the price gap between nanocrystalline cores and ferrite cores.

For high-power power supplies above 15 kW, nanocrystalline cores are already cheaper than ferrite cores in practical application. Restricted by maximum single-piece size of ferrite cores, multiple ferrite cores must be assembled to meet power demand for high-power transformers, while a single nanocrystalline core can fulfill the requirement independently. Although unit price of ferrite is lower, the total cost of multiple combined ferrite cores exceeds the cost of one nanocrystalline core.

Email: sales008@mycoiltech.com

Name：Alex~Mycoiltech