High-frequency inverter power supplies operate at a frequency range of 20 kHz to 50 kHz. The main transformer serves as the core component of a power supply. Although ferrite, the traditional magnetic core material, features relatively low high-frequency loss, it delivers unsatisfactory magnetic properties at frequencies below 100 kHz. In addition, its low saturation magnetic flux density (Bs) leads to larger size and heavier weight of magnetic cores. Furthermore, ferrite has a low Curie temperature and poor thermal stability. A slight temperature rise will reduce its Bs value, making the core susceptible to magnetic saturation and unstable operation, so it is not suitable for high-frequency and high-power operating conditions. With excellent comprehensive magnetic properties, nanocrystalline toroidal cores (ultra-microcrystalline cores) have become the premier choice as transformer cores for high-frequency  inverter power supplies nanocrystalline core

I. Advantages of Nanocrystalline Materials

Nanocrystalline toroidal cores integrate the advantages of silicon steel, permalloy and ferrite, detailed as follows:

High Magnetic Flux Density Its saturation magnetic flux density Bs is 1.2 T, twice that of permalloy and 2.5 times that of ferrite. The core achieves high power density ranging from 15 kW/kg to 20 kW/kg.

High Magnetic Permeability Its static initial permeability μ₀ can reach 120,000 to 140,000, equivalent to that of permalloy. For power transformer applications, Nanocrystalline Cores for High-Power Transformers is more than ten times that of ferrite, which greatly cuts down excitation power and improves transformer efficiency.

Low Core Loss Within the frequency band of 20 kHz to 50 kHz, its core loss is 1/2 to 1/5 of ferrite, effectively suppressing temperature rise of the magnetic core.

High Curie Temperature The Curie temperature of nanocrystalline toroidal cores is up to 570 °C, while the Curie temperature of ferrite is only 180 °C to 200 °C.

Benefiting from the above merits, transformers made of nanocrystalline cores greatly improve the reliability of inverter power supplies:

Low loss brings low temperature rise of transformers. Long-term practical application by numerous users proves that the temperature rise of high-permeability nanocrystalline transformer cores is far lower than that of IGBT devices.

High core permeability reduces excitation power and copper loss, boosting transformer efficiency. The large primary inductance of the transformer alleviates current impact on IGBT devices during switching operations.

High operating magnetic flux density brings a high power density of 15 kW/kg, realizing miniaturization of magnetic cores. Especially for high-power inverter power supplies, the smaller core size leaves more internal space inside the cabinet, facilitating heat dissipation of IGBT devices.

Strong overload resistance of the transformer. Since the operating magnetic flux density is set at approximately 40% of the saturation magnetic flux density, overload conditions only generate extra heat caused by increased magnetic flux, instead of damaging IGBT devices due to magnetic core saturation.

Thanks to the high Curie temperature of nanocrystalline toroidal cores, ferrite transformers will fail to work normally when the temperature exceeds 100 °C, whereas nanocrystalline transformers can operate stably without abnormality.

These superior properties of nanocrystalline materials have been recognized and adopted by an increasing number of power supply manufacturers. Many domestic manufacturers have adopted nanocrystalline cores and put them into practical use for years, and more manufacturers are starting formal adoption or trial application. At present, nanocrystalline cores are widely applied in inverter welding machines, communication power supplies, electroplating and electrolysis power supplies, induction heating power supplies, charging power supplies and other fields, and their application scale will expand significantly in the next few years.

Email: sales008@mycoiltech.com

Name：Alex~Mycoiltech

Amorphous and nanocrystalline soft magnetic materials feature outstanding properties. They offset the drawbacks of silicon steel and ferrite materials in various applications, upgrade all types of electronic products, raise efficiency and achieve remarkable energy-saving results, such as high-frequency main transformers and common-mode inductors for photovoltaic inverters, new energy vehicles, charging piles, amorphous alloy distribution transformers and so on. These new materials boast vigorous development vitality.

Now, an increasing number of people get to know amorphous magnetic cores and nanocrystalline magnetic rings (ultra-microcrystalline iron cores). Apart from transformers, amorphous magnetic cores and nanocrystalline magnetic rings can also be used as core materials for transformers, reactors, sensors, filters and other components. Their application scope covers household appliances in daily life including smart electric meters, DC inverter air conditioners, leakage protection switches; power systems such as power transmission, transformation and measurement, power distribution, remote measurement and sensing; railway systems like locomotive air conditioners, inverter power supplies for electric locomotives, railway signal sensing inductors and filters. They are also adopted and finalized for many military and national high-tech projects including aerospace, aviation and marine fields.

Please feel free to contact me for any product inquiries.

Email: sales008@mycoiltech.com

Name：Alex~Mycoiltech

Almost all nanocrystalline transformers are wound by complete machine manufacturers themselves. Different companies have different inverter circuit designs, different understandings of nanocrystalline cores, and different mastery of transformer making processes. As a result, transformers they make vary greatly in quality. Making high-frequency transformers is a key step in production. For this reason, some manufacturers hope to buy finished high-frequency transformers from professional suppliers instead of making them in-house.

High frequency transformers ferrite cores working at 20kHz to 50kHz , mostly U-type or EI-type, with a small number of O-type cores. U-type and EI-type cores are structurally hard to cut down transformer leakage inductance.

With the advantages of nanocrystalline cores, they become ideal materials to make smaller, more efficient high-frequency transformers, and help create a new structure for high-frequency transformers.

One patented design is named “Beetle” transformer. After further improvements, it became the patented “H-type” transformer. Both designs make full use of nanocrystalline cores’ features: high permeability, high magnetic flux density, low power loss and low magnetic leakage of ring cores. They adopt new primary and secondary winding structures. The metal shell protecting the core works as the secondary winding, fitting high-current output. The primary winding is wrapped evenly over the secondary winding, bringing very low leakage inductance. The fixing support and current output part are combined into one structure for better heat dissipation.

Advantages of this transformer:

High power: 10 kW ~ 20 kW, power density reaches 15 kW ~ 20 kW per kilogram

Low leakage inductance: normally below 5 μH, top versions less than 2 μH

High efficiency: over 99%

Small size and light weight: a 15 kW transformer weighs 3 kg, with dimensions 160×150×95 mm

Nice appearance

Due to special structure and complicated processing, this transformer has a relatively high price. It is now moderately used in electroplating and electrolysis power supplies, such as photovoltaic inverters, energy storage PCS, grid-tied inverters, off-grid inverters, main high-frequency transformers for energy storage, string inverters, commercial & industrial energy storage power supplies, residential energy storage systems, and nanocrystalline filter inductance cores for energy storage. It is hard to widely promote it in industries with fierce price competition. Therefore, the Ω-type transformer was developed.

The Ω-type transformer shares the same basic structure as common ring transformers, but with improved winding methods to lower leakage inductance and distributed capacitance. Its leakage inductance is generally below 10 μH. Its price is around 40% lower than Beetle-type or H-type transformers, attracting many manufacturers thanks to its good cost-performance.

Mass production of nanocrystalline transformers makes good use of the properties of nanocrystalline soft magnetic materials. It helps mass production and standardization of high-frequency power transformer cores, improves transformer efficiency and overall performance, and raises production efficiency for inverter welding machines, electroplating, electrolysis and other equipment. Several manufacturers are capable of producing such transformers at present. Some complete machine manufacturers have started to adopt Ω-type transformers for integrated production, which is an efficient, cost-saving and productive solution.

Email: sales008@mycoiltech.com

Name：Alex~Mycoiltech

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

In the research, production and mass manufacturing of switching power supplies, industrial control equipment and digital adapters, standard general electronic components can no longer meet the needs of precision equipment. Many magnetic components, including high-power through-hole filter inductors, EE13 power switching transformers and EE30 power drive transformers, need targeted customization. This is the key to ensuring stable operation of electronic products.

The through-hole filter inductor is a core component for equipment anti-interference, which mainly filters out EMI clutter in circuits. Different equipment has big differences in working frequency bands and current intensity. Standard inductors have fixed parameters, which often lead to insufficient filtering and excessive high-frequency interference. Customized inductors can adjust coil turns, core materials and pin spacing to fit the circuit features of different equipment. They also adapt to plug-in production processes, avoiding poor welding and low compatibility in mass production.

The EE13 power switching transformer is mostly used in small power adapters and low-voltage switching circuits. Such equipment has compact PCB space and strict requirements on component size and heat control. Standard EE13 switching transformers have single winding parameters, usually causing low energy conversion efficiency and serious equipment heat generation. Customization can accurately adjust core gaps and winding specifications to match the rated power of equipment, reduce size, lower power consumption and meet the miniaturization design needs of small devices.

Customization of the EE30 power drive transformer is especially important for medium and high-power industrial power supplies. As the core of power drive systems, it works under high voltage and large current, with strict standards for insulation voltage resistance and output stability.

Customization can optimize the frame structure, wire specifications and safety parameters, meet strict industrial certification standards, and greatly improve the stability and service life of industrial equipment. In short, component customization is not an unnecessary process. By customizing through-hole filter inductors and different types of EE transformers according to equipment demands, we can balance product performance, size and cost. It is an essential measure to improve the quality and production efficiency of electronic products.

Please feel free to contact me for any product inquiries.

Email: sales008@mycoiltech.com

Name：Alex~Mycoiltech