1K107 Nanocrystalline Toroidal Cores for High Permeability Transformers
Oct 27, 2025
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1K107 Nanocrystalline Toroidal Cores for Transformers
1K107 iron-based nanocrystalline toroidal cores combine ultra-high initial permeability with low high frequency core loss and a high saturation flux density. The closed magnetic path lets a design reach a target inductance with fewer winding turns and a smaller package than silicon steel or ferrite, and the material holds its performance across the medium to high frequency band from 50 kHz to 200 kHz. That combination suits common-mode chokes, current transformers and renewable energy inverters, where size, efficiency and stable behaviour over the operating range all matter.
Key Performance Features
High magnetic permeability: a high inductance is reached with fewer turns of wire, which reduces overall size and copper cost.
Low core loss: loss stays low at high frequency, giving higher efficiency and less heat generation inside the enclosure.
High saturation flux density: more flux can be handled before saturation, which is essential in high current applications such as power transformers and inverters.
Excellent high frequency behaviour: permeability remains high and loss remains low across a wide frequency range.
High Curie temperature: performance is stable over a wide operating range, and continuous operation up to 120 °C or higher is achievable.
Low audible noise: the toroidal shape and material properties keep magnetostrictive stress and the resulting noise to a minimum.
Toroidal Cores Compared with Silicon Steel and Ferrite
The table positions the nanocrystalline toroid against a 30Q130-class silicon steel toroid and a Mn-Zn ferrite toroid. Figures are indicative and depend on grade, test frequency and temperature.
| Parameter | Nanocrystalline toroidal | Silicon steel toroidal (30Q130 class) | Ferrite toroidal (Mn-Zn) |
|---|---|---|---|
| Operating frequency range | 50 kHz - 200 kHz | 50 Hz - 1 kHz | 100 kHz - 1 MHz |
| Core loss at 100 kHz | 15-30 W/kg | 120-180 W/kg | 8-15 W/kg (strongest at ultra-high frequency) |
| Initial permeability | 50,000-200,000 | 3,000-5,000 | 1,000-10,000 |
| Saturation induction Bs | 1.2-1.5 T | 1.8-2.0 T | 0.3-0.5 T |
| Power density at equal volume | 5-10 kW/L | 1-2 kW/L | 2-3 kW/L in ultra-high frequency duty |
| Magnetic leakage | 3% or less | 8% or less | 2% or less |
| Relative cost | 3.0-4.0 | 1.0 as benchmark | 1.8-2.5 |
| Preferred duty | Medium to high frequency, miniaturisation | Power frequency, high power | Ultra-high frequency, low power |
Typical Ring Dimensions and DC Overcurrent Class
Each ring is described by the bare core size, the matching protective box, the effective cross sectional area Ae, the magnetic path length Ie and the maximum DC overcurrent class.
| Core id (mm) | Core od (mm) | Core ht (mm) | Box ID (mm) | Box OD (mm) | Box HT (mm) | Ae (mm2) | Ie (mm) | Max DC overcurrent class (A) |
|---|---|---|---|---|---|---|---|---|
| 14 | 19 | 6.5 | 12 | 22 | 8 | 11.86 | 51.81 | 20 |
| 14 | 20 | 10 | 12 | 22.3 | 11.4 | 29.68 | 52.29 | 40 |
| 16 | 21 | 10 | 15 | 24 | 12.3 | 24.85 | 57.41 | 60 |
| 16 | 23 | 8 | 15 | 24 | 9.7 | 20.44 | 61.23 | 60 |
| 16 | 23 | 10 | 15 | 24 | 12.3 | 34.62 | 59.92 | 60 |
| 17 | 22 | 10 | 15.3 | 24.4 | 12.3 | 24.86 | 60.59 | 60 |
| 17 | 21 | 8 | 15.3 | 24 | 9.7 | 25.56 | 60.67 | 60 |
| 17 | 23 | 8 | 15.3 | 24.4 | 9.7 | 26.89 | 61.34 | 60 |
Sizes beyond this list, including larger diameters and higher overcurrent classes, are wound to order so that a toroid can be matched to a specific inverter, choke or current transformer design.
Application Fit: Chokes, Current Transformers and Inverters
Common-mode chokes in EMC filters: high inductance and a flat frequency response give effective filtering of common-mode noise in switched-mode supplies.
Current transformers: high permeability and saturation induction produce good accuracy and linearity over the measured current range.
Power inverters: solar and wind inverters, uninterruptible power supplies and switched-mode supplies all benefit from the combination of high efficiency and compact size.
Other duty: magnetic amplifiers, DC to DC converter inductors and audio output inductors also use the material where low loss and low noise are required.
Selection usually starts from the inductance needed at the switching frequency, then checks that flux density stays below saturation at peak current, that the DC bias stays inside the overcurrent class of the chosen ring, and that the finished ring with its box fits the mechanical envelope. Where the duty is pure power frequency at high power, silicon steel remains competitive; where the frequency is very high and the power low, ferrite is often the more economical answer.
Frequently Asked Questions
Q: What frequency band do 1K107 toroidal cores cover?
The material is normally used from about 50 kHz to 200 kHz, where its loss advantage over silicon steel is greatest and ferrite has not yet taken the lead.
Q: How much lower is core loss than silicon steel?
At 100 kHz a nanocrystalline toroid dissipates roughly 15-30 W/kg, against 120-180 W/kg for a 30Q130-class silicon steel toroid of similar size, a reduction of several times.
Q: Why does the toroidal shape help?
The closed ring confines flux inside the magnetic path, which limits leakage to about 3% or less and suppresses the magnetostrictive noise that open laminated stacks can produce.
Q: Can the core handle DC bias current?
Yes, within the stated DC overcurrent class, which ranges from about 20 A on the smallest rings to 120 A and beyond on larger rings. Operation close to that limit reduces inductance.
Q: What is the maximum continuous operating temperature?
Continuous operation at 120 °C or higher is possible because of the high Curie temperature, and the magnetic parameters drift only slightly across the industrial temperature range.
Q: Are dimensions and boxes customizable?
Core inner diameter, outer diameter, height, box format and electrical parameters including effective area and path length can all be produced to a customer drawing.