1K107 Nanocrystalline Iron Core for Low-Loss Transformer Design

1K107 Nanocrystalline Iron Cores in Power Conversion

1K107 nanocrystalline iron cores are soft magnetic components made from iron-based nanocrystalline alloy ribbon. The alloy contains iron together with silicon, boron, copper and niobium. The strip is first produced by rapid solidification such as melt spinning into an amorphous ribbon, then annealed at low temperature so that a nanoscale grain structure of roughly 5-50 nm develops, and finally wound, cut or bonded into a finished core. The result combines the high permeability of amorphous alloys with the magnetic stability of grain-oriented silicon steel, which is why these cores are widely used in power electronics, new energy converters and electromagnetic compatibility filters.

Typical Physical Properties and Comparison

The values below cover the magnetic and thermal parameters that dominate core selection for transformers, chokes and inductors. The comparison column refers to a conventional 30Q130-class grain-oriented silicon steel.

Loss figures quoted at 0.5 T and 50 Hz follow the IEC 60404 magnetic materials measurement series. They are indicative only: grade, ribbon thickness, winding factor and excitation waveform all shift the realised value, so the material data sheet for the delivered batch remains the reference for design work.

Core Loss and Permeability at Medium and High Frequency

Core loss combines hysteresis loss and eddy current loss, and the nanocrystalline structure suppresses both mechanisms at the same time.

Hysteresis loss: the nanocrystalline grains present little resistance to domain wall movement, so coercivity is only about one tenth to one twentieth of that of silicon steel. Because hysteresis loss is proportional to coercivity, it falls by a similar ratio.

Eddy current loss: ribbon thickness is typically 15-30 µm and resistivity is about 1.3×10⁻⁶ Ω·m, against about 0.45×10⁻⁶ Ω·m for silicon steel. Eddy current loss decreases with the square of ribbon thickness and with resistivity, so both properties work in favour of the nanocrystalline core.

Practical effect: in switching supplies operating above 50 kHz and in charging pile modules, loss can be one fifth to one tenth of that of a comparable silicon steel core, which raises converter efficiency and reduces the heat that has to be removed from the enclosure.

Initial permeability of 1K107 reaches 50,000-200,000, far above the 3,000-5,000 of silicon steel and the 10,000-30,000 of amorphous alloys. In current transformers, voltage transformers and residual current devices this high value produces a usable secondary signal from a weak primary field, improving conversion accuracy and shortening protection response time, and it also allows the turn count to be reduced for a target inductance, which saves copper and winding labour.

Stability, Ageing and Mechanical Strength

Thermal stability: grains are small and uniformly distributed and the lattice remains stable after annealing. The Curie temperature of 400-450 °C sits above that of amorphous alloys, and across -50 to 150 °C the drift in permeability and loss is normally below 5%, against 10-15% for amorphous cores.

Ageing behaviour: amorphous alloys can lose magnetic performance through structural relaxation during long storage, while the annealed nanocrystalline structure stays stable, with attenuation below 3% over ten years of service.

Mechanical properties: ribbon tensile strength is about 1500 MPa, roughly three times the 500 MPa of silicon steel, so wound cores resist cracking during handling and assembly. Ring, C-type and rectangular shapes can be produced by winding, cutting and bonding to suit the space available in the equipment.

Standard Dimensions and Custom Ring Sizes

Wound rings are supplied in the dimension sets below. OD and ID set the magnetic path geometry and H is the build height of the winding.

Sizes outside this list can be produced to customer drawings, including cut C-type and rectangular formats. The annealed winding is supplied bare or fitted into a protective box, and the box format is chosen to match the winding equipment used by the transformer builder.

Frequently Asked Questions

Q: When is a 1K107 nanocrystalline iron core preferred over silicon steel?
Above a few kilohertz, and especially between 50 kHz and 200 kHz, the loss advantage of several times over makes the compact nanocrystalline core the better choice. At pure power frequency with very high power, silicon steel remains the economical option.

Q: What core loss can be expected at 0.5 T and 50 Hz?
Typical values fall in the range of 0.15-0.3 W/kg, which is 60-80% below the 1.0-1.5 W/kg of a comparable 30Q130 silicon steel core.

Q: How high is the saturation flux density?
Saturation induction is typically 1.2-1.5 T, a little below the 1.8 T of grain-oriented silicon steel but well above ferrite, which keeps the core compact at moderate flux levels.

Q: What is the usable operating temperature range?
Continuous service from -50 to 150 °C is normal, with the Curie temperature at 400-450 °C. Loss and permeability drift by less than 5% across that band.

Q: Can the ring be delivered inside a protective box?
Yes. Bare wound rings and boxed rings are both available, and the box identity, outer diameter and height are matched to the ring so that the winding window stays predictable.

Q: Are non-standard sizes available?
Custom outer diameter, inner diameter, build height and cut formats such as C-type can be produced against a drawing, including sizes larger than the standard list above.