Nanocrystalline cores for EMI protection, current transformer and power transformation

Nanocrystalline cores – high-performance solutions for transport, energy and industry

Nanocrystalline cores are the perfect solution for EMI shielding applications (common mode chokes CMC), mid-frequency transformers up to about 80kHz, current transformers (CT), and sensors for residual current devices (RCD).

Our nanocrystalline cores cover a permeability range from 5000 to several 100,000 and have a saturation induction of up to 1.7 T, maintaining low losses for compact designs. We offer special hysteresis loops (R, Z) and various shapes, including toroids, oval, rectangular shapes, E-cores, bars, and custom designs made from thin ribbon.

At our Magnetics Products Technology Centre, managing our brand Acal BFi kOr, we support you in selecting the right material, shape, and finish for your application. Our team is dedicated to developing customised products quickly and efficiently, ensuring you get the best solution for your needs.

Product ranges in nanocrystalline cores

Nanoperm Nanocrystalline Cores
Magnetec
Nanoperm Nanocrystalline Cores

Nanocrystalline soft magnetic tape wound cores for EMI, specially designed to reduce motor-bearing currents.

Nanocrystalline magnetic cores Acal BFi kOr
Acal BFi kOr
Nanocrystalline magnetic cores Acal BFi kOr

Customised nanocrystalline cores for power and EMC applications as well as current transformers (CT) and residual current circuit breakers (RCCB).

Nanocrystalline cores
Magnetics Inc.
Nanocrystalline cores

Nanocrystalline cores are ideal for common mode chokes due to their high permeability, low loss, and high saturation (1.25 T). They offer smaller size, higher current capacity, and better performance than ferrite cores, especially at high frequencies and temperatures.

Nanocrystalline Core FAQs – Properties, Materials, and Applications

Frequently Asked Questions about Nanocrystalline Cores

These are metal alloys that are rapidly cooled from the melt into ribbons about 20 µm thick using a rapid solidification process. The sudden cooling preserves an amorphous (glassy) structure. Some alloys are used directly in this state as amorphous magnetic materials. For nanocrystalline materials, a subsequent heat treatment – sometimes in a magnetic field – produces a nanostructure that results in outstanding magnetic properties: high permeability, low losses, low magnetostriction, and a high saturation induction (>1.2 T).

The ribbon is cut to width and wound into ring-shaped cylinders (toroidal cores). If needed, these are fixed into other shapes (oval, rectangular) using templates. This is followed by a heat treatment in a protective atmosphere, sometimes in a magnetic field, to relax the core and set the target magnetic properties. The core is then coated or bonded into a housing, and optionally impregnated for additional stability.

One fascinating aspect of nanocrystalline materials is their flexibility. By adjusting the heat treatment, a wide range of magnetic properties can be set:

  • Flat (linear) hysteresis loops with permeabilities from a few thousand up to around 200,000
  • Round loops with maximum permeabilities up to 600,000
  • Rectangular loops with remanence levels of 90–97 % of the saturation induction

Thanks to 3–4 times higher saturation induction, superior permeability up to about 100 kHz, and high temperature resistance (up to 200 °C), nanocrystalline cores are ideal for:

  • Compact, low-loss transformers (5–100 kHz)
  • Space-saving broadband common mode chokes (CMC)
  • High-accuracy current transformers and RCD sensors
  • Certain types of push-pull inductors

They are particularly used in automotive, aerospace, installation technology, and robotics industries.

Yes, several material classes exist. For industrial applications, one material offering the best cost-performance ratio has become standard – originally developed under the Finemet brand by Hitachi Metals, now available in many variants.

Magnetostriction describes the interaction between magnetisation and mechanical deformation. It can cause unwanted effects like transformer noise (buzzing) or changes in magnetic properties under mechanical stress. With optimised processes, such as using Acal BFi kOr 120 material, practical magnetostriction-free performance is achieved, enabling stable permeabilities above 100,000.

The quality of nanocrystalline cores depends on the process stability during both ribbon and core production. Only a few manufacturers worldwide guarantee consistent ribbon quality. Reliable core manufacturers have long-term experience in series production and offer customised designs using high-quality materials.

Acal BFi offers the magnetostriction-free standard material kOr 120, as well as specialised variants kOr 118 and kOr 122. Ring cores and cut tape cores are available in established standard sizes. On request, Acal BFi develops customised solutions regarding shape, dimensions, permeability, remanence, cuts, air gaps, housings, or coatings – efficiently and cost-effectively.

Permeability (µ) describes the ability to guide magnetic flux. High permeability increases inductance or impedance, ideal for transformers, common mode chokes, or RCD sensors. At high frequencies, effective permeability drops, so low-loss materials become more critical. Lower permeability allows for higher saturation currents, beneficial in push-pull chokes and DC-sensitive current transformers.

Cutting impregnated cores introduces air gaps that reduce effective permeability (typically 2,500–10,000) and allow winding on bobbins. Larger air gaps can be added to further reduce permeability and improve saturation resistance and linearity – offering advantages over powder cores with comparable permeability.

Coated cores or housed cores can be wound directly with enamelled copper wire. For separating windings in transformers or common mode chokes, spacers can be used. Cut tape cores are usually mounted on bobbins without coating. For high-current applications, cables or busbars are often passed directly through ring or oval cores.