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Nanocrystalline Cores and Amorphous Cores in Transformers
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Nanocrystalline Cores and Amorphous Cores in Transformers
The advent of nanocrystalline cores and amorphous cores has provided ideal materials for medium and high-frequency transformers. With industrial development, the operating frequency of power supplies has increased to 20kHz, and the output power exceeds 30kW. Traditional core materials, such as silicon steel sheets, suffer from high losses and cannot meet the demands of new requirements in power supplies.
Amorphous and iron-based nanocrystalline cores have significant application value in high-power & high-frequency transformers due to their high saturation magnetic induction strength, high permeability, low loss, good temperature stability, and environmentally friendly manufacturing processes.
Nanocrystalline Cores
Nanocrystalline materials primarily consist of iron, chromium, copper, silicon, and boron. These specific alloy components are manufactured into an amorphous state using rapid quenching technology, followed by heat treatment to produce nanometer-sized crystalline grains.
Nanocrystalline cores exhibit excellent magnetic properties and temperature stability, particularly suitable for replacing ferrites in transformers below the 20kHz to 50kHz frequency range.
The resistivity of nanocrystalline materials is 90μΩ.cm (after heat treatment). Due to their nanostructure, they combine the advantages of silicon steel, permalloy, and ferrite.
Ordinary iron-based nanocrystalline soft magnetic materials have a thickness of about 30μm. Due to their brittleness, and sensitivity to stress, their magnetic properties can be significantly reduced if subjected to external forces during processing and use. Therefore, nanocrystalline cores are typically manufactured into ring or horseshoe shapes and housed in protective casings. Nanocrystalline cores’ heat dissipation performance is affected by the protective casing material.
New kinds of nanocrystalline cores have been used in transformers. The thickness of nanocrystalline materials is only 24μm. After heat treatment, the solidified cores have significant advantages over traditional transformer cores:
※ The new nanocrystalline cores, wrapped with insulating film, achieve the strength required for winding and can be directly wound into transformers.
※ The cured nanocrystalline cores eliminate the protective casing, allowing for greater heat dissipation space and improved transformer operational safety.
※ This design reduces the impact of the protective casing material on nanocrystalline cores and saves on the structural design and molding time for the protective casing.
※ The design for nanocrystalline cores can be more flexible, offering various shapes such as toroidal, rectangular, and C-shaped cores, providing more options for transformer design and subsequent winding processes.
Amorphous Cores
Amorphous materials are produced using ultra-rapid quenching technology, with a cooling rate of approximately one million degrees per second. This technology solidifies molten steel into alloy strips with a thickness of 30 micrometers in a single step. Due to the rapid cooling, the metal does not have time to crystallize, resulting in no grains or grain boundaries in the alloy, thus forming what is known as an amorphous alloy.
Amorphous metals have a unique microstructure that differs from conventional metals. Their composition and disordered structure endow them with many unique properties, such as excellent magnetism, corrosion resistance, wear resistance, high strength, hardness, toughness, high resistivity, and high electromechanical coupling coefficients.
The main components of iron-based amorphous cores are iron, silicon, and boron. With a silicon content as high as 5.3% and the unique structure of the amorphous state, their resistivity is 130μΩ.cm, which is twice that of silicon steel sheets (47μΩ.cm).
The thickness of iron-based amorphous materials used in amorphous cores is about 30nm, much thinner than what silicon steel sheets can achieve. Consequently, their eddy current loss is low during high-frequency operation, and within the frequency range of 400Hz to 10kHz, their loss is only 1/3 to 1/7 of that of silicon steel sheets. Additionally, the permeability of iron-based amorphous cores is much higher than traditional cores.
Due to these advantages, amorphous cores reduce transformer weight by more than 50% and lower temperature rise by 50%.
After years of development, besides being used in high-frequency transformers, amorphous and nanocrystalline cores have been widely applied in current transformers, switching power supplies, and electromagnetic compatibility devices.
Amorphous and Nanocrystalline Cores Provider: Leimai
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