In the field of modern power electronics, soft magnetic materials play an increasingly crucial role, their performance directly impacting the overall efficiency of power conversion, transmission, and control equipment. From residential power systems to industrial-grade power facilities, soft magnetic materials are the core foundation for achieving efficient power processing, and their application scope continues to expand as global demands for energy conservation and low-carbon development continue to rise.
Choosing the right core material is a key step in improving the energy efficiency of power electronic devices and reducing energy loss. As the "heart" of core components such as inductors and transformers, the magnetic properties of the core directly determine the operating losses, temperature rise, and stability of the equipment. Inappropriate material selection can not only increase energy consumption but also shorten the lifespan of the equipment and increase maintenance costs.
Among numerous soft magnetic materials, amorphous cores and nanocrystalline cores have become popular choices in the current power electronics field due to their excellent magnetic properties. This article will focus on these two core materials, providing a detailed analysis from the aspects of structure, manufacturing, characteristics, and application scenarios, offering comprehensive technical references for relevant practitioners.
Amorphous cores are made of amorphous alloys (also known as metallic glasses). Their most significant characteristic is the disordered arrangement of atoms—unlike the regular lattice structure of traditional crystalline materials, the atoms in amorphous alloys do not have time to form an ordered arrangement during solidification, ultimately forming a glass-like amorphous structure. This unique structure is the core source of their superior magnetic properties.
The manufacturing of amorphous cores relies on rapid solidification technology: molten alloy (usually composed of elements such as iron, silicon, and boron) is sprayed through special nozzles onto high-speed rotating cooling rollers. The alloy melt cools rapidly at rates in the millions of degrees per second, skipping the crystal formation stage and directly forming amorphous ribbons only tens of micrometers thick. Subsequently, these ribbons are cut, stacked, wound, and subjected to subsequent insulation treatments to ultimately produce amorphous cores of different specifications.
High Permeability: The disordered atomic structure reduces the resistance to magnetic domain movement, allowing amorphous cores to achieve rapid changes in magnetic flux even under low magnetic fields, exhibiting excellent magnetic permeability.
Low Coercivity: Hysteresis loss is positively correlated with coercivity. The low coercivity of amorphous materials significantly reduces hysteresis loss and improves energy conversion efficiency.
Low Iron Loss: The resistivity of amorphous alloys is much higher than that of traditional silicon steel sheets, effectively suppressing eddy current generation. Combined with the advantage of low hysteresis loss, its overall iron loss is significantly lower than that of traditional magnetic core materials.
Amorphous magnetic cores, due to their low loss and high cost-effectiveness, are widely used in energy- and cost-sensitive fields, including:
Distribution transformers (especially energy-saving distribution transformers);
Power conversion equipment such as switching power supplies and uninterruptible power supplies (UPS);
Inductors, reactors, and other components in industrial control.
For developing markets, the cost-effectiveness and availability of amorphous cores are their core advantages. On the one hand, the manufacturing cost of amorphous cores is relatively controllable, requiring no complex crystal manipulation processes. On the other hand, their compatibility with energy-saving transformers and other equipment helps developing markets achieve long-term energy savings while controlling initial investment, meeting the needs of regional energy structure optimization.
Definition and Structure
The matrix material of a nanocrystalline magnetic core is a nanocrystalline alloy. Its structural characteristic is the uniform distribution of ultrafine crystalline particles with a size of only 5-50 nanometers within the disordered matrix of the amorphous alloy. This composite structure of "amorphous matrix + nanocrystalline particles" combines the low-loss characteristics of amorphous materials with the high magnetic stability of crystalline materials, achieving further optimization of magnetic properties.
Manufacturing Method
The manufacturing of nanocrystalline cores is based on amorphous ribbons. The core step is controlled annealing: first, an amorphous ribbon is prepared using rapid solidification technology, and then the ribbon is annealed at a specific temperature (usually 400-500℃). During the annealing process, some atoms in the amorphous matrix rearrange to form uniformly dispersed ultrafine nanocrystalline particles. After annealing, the particles undergo winding, shaping, and insulation treatment to ultimately produce a nanocrystalline magnetic core.
Extremely High Permeability: The presence of nanocrystalline particles further optimizes the magnetic domain structure, resulting in a significantly higher permeability for nanocrystalline cores compared to amorphous cores, especially at low frequencies.
Ultra-Low High-Frequency Loss: Thanks to its ultra-fine grain structure and high resistivity, nanocrystalline cores maintain extremely low iron losses even at high frequencies (tens to hundreds of kHz), making them suitable for high-frequency power electronic devices.
Excellent Temperature Stability: The nanocrystalline structure exhibits strong thermal stability, with minimal changes in magnetic properties (such as permeability and loss) over a wide temperature range (typically -50℃ to 150℃), allowing it to adapt to complex temperature environments.
Moderate Saturation Flux Density: The saturation flux density is approximately 1.2T, falling between that of amorphous cores and traditional silicon steel sheets. This satisfies the flux requirements of most power electronic devices while avoiding magnetic saturation problems caused by excessively high flux densities.
Due to their high-frequency, low-loss, and excellent temperature stability, nanocrystalline cores are primarily used in fields with stringent performance requirements, including:
Common-mode inductors and differential-mode inductors (for suppressing electromagnetic interference);
On-board inverters and filters for electric vehicles (EVs);
High-frequency transformers (such as those used in communication power supplies and photovoltaic inverters);
Precision current transformers and voltage transformers (for power metering and monitoring).
For industrial users, the durability and adaptability to harsh environments of nanocrystalline cores are their core value. In high-temperature and high-humidity environments such as tropical regions and high-temperature workshops, nanocrystalline cores maintain stable magnetic properties and are not easily affected by environmental factors leading to performance degradation or failure. Simultaneously, their excellent vibration and shock resistance meet the reliability requirements of long-term continuous operation of industrial equipment, reducing equipment maintenance frequency and costs.
Amorphous Cores: Atoms are completely disordered, with no obvious crystalline structure, exhibiting a uniform "glassy" state.
Nanocrystalline Cores: Based on disordered amorphous materials, with uniformly distributed ultrafine nanocrystalline particles (5-50nm in size) inside, belonging to an "amorphous + nanocrystalline" composite structure.
Permeability and Loss Level:
Permeability: The permeability of nanocrystalline cores is much higher than that of amorphous magnetic cores, especially at low frequencies.
Loss Level: At low frequencies (e.g., 50/60Hz), the difference in loss between the two is small; however, at high frequencies (>20kHz), the loss of nanocrystalline cores is much lower than that of amorphous magnetic cores.
Frequency Range Applicability:
AmorphousCores: More suitable for low to mid-frequency ranges (typically ≤20kHz), such as power frequency distribution transformers.
Nanocrystalline Cores: Suitable for mid-to-high frequency ranges (20kHz to several hundred kHz), such as high-frequency inverters and automotive electronic equipment.
Temperature Performance:
AmorphousCores:Offer better temperature stability, but at high temperatures (>100℃), the magnetic performance degradation is slightly greater than that of nanocrystalline magnetic cores.
Nanocrystalline Magnetic Cores: Provide superior temperature stability, exhibiting minimal magnetic performance changes within the -50℃ to 150℃ range, making them suitable for more complex temperature environments.
Cost vs. Performance Trade-off: Amorphous cores have lower raw material and manufacturing costs, making them suitable for cost-sensitive applications with lower high-frequency performance requirements. Nanocrystalline magnetic cores, due to the added controlled annealing process, have a relatively higher cost but offer superior high-frequency performance and temperature stability, making them suitable for high-value-added, high-performance equipment.
Selection Logic:If the project primarily involves low-frequency applications (e.g., power frequency transformers), has a limited budget, and prioritizes basic energy-saving effects, amorphous cores should be prioritized. If the project involves high-frequency operations (e.g., EV inverters) and has high temperature stability requirements, nanocrystalline cores should be chosen even if the cost is slightly higher.
Operating frequency is the core factor in magnetic core selection:
If the equipment operates in the low-frequency range (e.g., 50/60Hz power frequency), such as in distribution transformers, amorphous cores offer better cost-effectiveness.
If the equipment operates in the mid-to-high frequency range (>20kHz), such as in high-frequency inverters and automotive filters, nanocrystalline cores should be prioritized to avoid excessive high-frequency losses leading to excessive temperature rise.
A comprehensive judgment should be made based on the equipment's energy efficiency targets and long-term operating costs:
If the primary goal is basic energy saving with short long-term operating times (e.g., small power supplies operating intermittently), amorphous cores can meet the requirements.
If the equipment needs to operate continuously for extended periods (e.g., in industrial transformers and new energy power plant inverters), even with a slightly higher initial investment, choosing nanocrystalline cores can achieve long-term energy savings through lower losses, reducing overall operating costs.
Environmental factors directly affect the lifespan and stability of magnetic cores:
If the equipment is installed in a dry, normal-temperature environment (such as an indoor power distribution room), both amorphous and nanocrystalline cores are suitable;
If the equipment needs to operate in high-temperature (>100℃), high-humidity, or temperature-fluctuation environments (such as tropical outdoor equipment or automotive electronics), nanocrystalline cores with stronger temperature stability should be selected.
For customers in developing markets, a balance must be found between cost control and performance requirements:
If the project budget is limited and the application scenario is low-frequency basic power equipment (such as rural power distribution transformers), amorphous cores have a more significant cost advantage;
If the project involves high-value-added equipment (such as precision testing instruments or new energy vehicle components), performance should be prioritized, and nanocrystalline cores should be selected to avoid equipment failure due to insufficient material performance.
Magnetic core selection involves matching multiple dimensions of technical parameters. It is recommended to consult professional magnetic core suppliers (such as BIDRAGON). Our professional team can provide customized magnetic core solutions based on the specific parameters of your equipment (such as power, frequency, and temperature rise requirements), including material selection, structural design, and performance testing, ensuring a perfect fit between the magnetic core and the equipment.
Amorphous and nanocrystalline cores each have their advantages: amorphous cores are characterized by high cost-effectiveness, low frequency, and low loss, making them suitable for cost-sensitive low-frequency power equipment; nanocrystalline cores, with their high frequency, low loss, and excellent temperature stability, are the preferred choice for high-performance high-frequency equipment.
When selecting a magnetic core, price should not be the sole criterion. Instead, the operating frequency, efficiency requirements, environmental conditions, and long-term operating costs of the equipment should be considered to choose the most suitable material. Only by accurately matching the application scenario can the performance advantages of the magnetic core be fully utilized, achieving efficient and stable operation of the equipment.
If you are looking for a suitable magnetic core solution for your next project, please contact our technical team. We will provide you with professional technical support and customized solutions to help your equipment achieve a dual improvement in performance and efficiency.