Overcoming Performance Bottlenecks: Why Gradient High-Silicon Steel (JNHF) Achieves Zero Loss Deterioration in High-Frequency Reactors

I. The "Processing Degradation" Dilemma

Design engineers frequently rely on raw material datasheets when selecting core materials. However, in real-world manufacturing, different soft magnetic materials exhibit drastically different degrees of core loss deterioration once processed into finished cores:

• Fe-Based Amorphous Alloys: Featuring an ultra-thin ribbon gauge of just 0.025 mm, amorphous ribbons exhibit extremely low raw material core loss. However, they are exceptionally sensitive to mechanical stress. Even after stress-relief annealing, winding into C-cores, cutting, and assembly result in a 68% loss deterioration rate (jumping from a raw material loss of 1.31 W/kg to 2.20 W/kg in the finished core @ 20 kHz, 0.05 T).
• Thin-Gauge Grain-Oriented Steel (GO): Due to its strong magnetic anisotropy, GO steel must be manufactured as wound C-cores. Subject to winding stress and assembly constraints, it experiences a ~5% core loss degradation (increasing from 9.75 W/kg to 10.24 W/kg).
• Gradient High-Silicon Steel (JNHF-Core): By employing precision stamping/cutting combined with a glued block-type stacked lamination structure (Stacked Core), empirical data proves that JNHF achieves a 0% core loss deterioration rate in finished cores (4.89 W/kg raw material vs. 4.88 W/kg finished core).

Core Loss Degradation Comparison: Raw Material vs. Finished Core (20 kHz, 0.05 T)

II. Structural Innovation: Air Gap Dispersion Effect Suppresses Localized Overheating

To prevent magnetic saturation under high DC currents, air gaps must be introduced into the magnetic circuit of DC/AC high-frequency reactors. However, conventional concentrated air gaps generate severe fringing flux (leakage flux), inducing large localized eddy currents in adjacent laminations and causing intense localized hot spots.

Concentrated Air Gap vs. Multi-Gap Dispersion Performance

1. Conventional Wound C-Cores: Restricted by their geometry, C-cores typically rely on 1 or 2 large concentrated air gaps. As the total gap length increases (e.g., to 4 mm), intense fringing flux causes the core loss of amorphous and GO steel cores to rise exponentially.
2. JNHF Glued Block-Type Stacked Cores: Leveraging the non-oriented (NO) nature and superior mechanical behavior of high-silicon steel, JNHF can be configured as a multi-segment assembled block core, dividing a single large air gap into multiple smaller, distributed gaps:
   • For the same total air gap length (e.g., 4 mm), the length of each individual gap is drastically reduced;
   • Fringing flux is effectively contained, substantially suppressing fringing-induced losses;
   • Test results confirm that as total gap length expands from 0 mm to 4 mm, the core loss curve of JNHF remains remarkably flat, yielding significantly lower real-world losses at higher air gap lengths compared to amorphous and GO steel cores.

III. Dual Permeability Advantage: Superior DC Bias Resistance & High-Frequency Inductance Retention

For DC reactors in power electronics (such as Boost circuits, PFC inductors, and DC-DC converters), the DC bias characteristics of the core directly govern inductance stability under high load currents.

Excitation tests at 20 kHz, 0.01 T demonstrate:

• Amorphous & GO Steel Cores: When the DC bias ampere-turns exceed 2,000 A·t, inductance (μH / turn²) drops sharply off a cliff.
• JNHF Gradient Cores: Under high DC bias (from 2,000 A·t up to 4,000 A·t), JNHF displays an exceptionally smooth magnetic saturation roll-off, maintaining high residual inductance levels.

Mechanism: How Does JNHF Achieve High Bias Resistance & High Inductance?

JNHF utilizes a silicon gradient structure across the sheet thickness (high silicon ~6.5% Si at the surface, lower silicon at the center):

1. Low DC Permeability (μ_max = 4,100): Compared to standard silicon steel (37,000) and amorphous alloys (300,000), JNHF features a lower DC permeability, providing strong intrinsic resistance to DC magnetic saturation.
2. High High-Frequency Permeability (μ_20kHz = 1,500): At 20 kHz, JNHF retains a high AC permeability of 1,500 (outperforming GO steel's 1,110), ensuring abundant inductance under high-frequency current ripple.

IV. Youyou Technology: One-Stop Precision Processing Solutions for High-Silicon Steel Cores

Youyou Technology Co., Ltd. specializes in precision stamping and self-bonding lamination for motor stators and high-frequency reactor cores. Tailored to the unique characteristics of JFE Super Core materials (JNHF-Core and 6.5% Si JNEX-Core), we provide comprehensive custom manufacturing solutions:

1. 0.10 mm Ultra-Thin High-Silicon Steel Stress-Free Self-Bonding Lamination

For 0.10 mm ultra-thin JNHF sheets, we utilize interlock-free, weld-free self-bonding/gluing technology. Eliminates inter-lamination short circuits and eddy current loops caused by traditional riveting or welding, fully unlocking 100% of the material's native high-frequency performance.

2. Precision Stamping & Custom Multi-Gap Block Cores

Equipped with ultra-precision stamping and micro-cutting capabilities, we engineer and process custom multi-gap block-type cores tailored to your inductance and DC bias requirements. Helps power electronics designers control leakage flux heat and reduce overall reactor footprint and weight.

3. Near-Zero Magnetostriction Ultra-Quiet High-Frequency Cores

For noise-sensitive applications (such as automotive inverters, medical equipment, or residential power units), we offer processing solutions based on 6.5% Si JNEX-Core, achieving near-zero magnetostriction for ultra-quiet operation alongside low high-frequency core loss.

About YouYou Company

As a specialized manufacturer of high-precision motor lamination stacks and high-frequency reactor cores in China, YouYou Company delivers state-of-the-art precision stamping, 0.10mm ultra-thin self-bonding (Backlack) lamination, and gradient high-silicon steel (JNHF/JNEX) processing services. We provide global OEMs and Tier-1 suppliers with end-to-end soft magnetic solutions—ranging from material selection and rapid multi-gap block core prototyping (Micro-Wire EDM / Self-Bonding) to high-volume automated production with zero core loss degradation.