FeNi vs Sendust Powder Cores: Comparison for PFC & High-Current Inductors

FeNi and Sendust are both metal powder cores with distributed air gaps, but they are not interchangeable. Engineers often pick between them for PFC inductors, buck converters and high-current DC-DC stages — and the wrong choice costs either board space or efficiency. This side-by-side comparison covers the properties that decide the part.

1. Saturation flux density (Bs)

FeNi (50% Fe, 50% Ni) powder cores — also called High Flux cores — reach a saturation flux density of Bs ≥ 1.5 T. Sendust (Fe-Si-Al, also branded Kool Mu) saturates around 1.05 T. The ~40% difference means a FeNi core can carry roughly 40% more current in the same volume, or deliver the same inductance in a significantly smaller package. When the inductor sees high peak current or tight board space, FeNi wins.

2. Core loss at operating frequency

Frequency range	FeNi (High Flux)	Sendust (Kool Mu)
20–100 kHz	≤ 300 kW/m³ (at 100 mT)	Lower loss at low flux swings
100 kHz – 500 kHz	Usable, loss rises with frequency	Typically lower loss than FeNi
> 500 kHz	Loss climbs; ferrite usually better	Also lossy; ferrite preferred

Sendust generally has lower core loss than FeNi in the 20–500 kHz range at the same flux swing, which is why it is popular for PFC and line-frequency converters. At very high current and high flux density, however, FeNi can end up more efficient simply because you need a much smaller core.

3. DC bias and permeability roll-off

Both materials use a distributed air gap, so inductance rolls off gradually instead of dropping sharply. FeNi cores typically keep higher percentage of initial permeability under heavy DC bias, especially at elevated temperature. For inductors with large DC components — server POL, EV chargers, AI GPU VRM — FeNi delivers more usable inductance at full load.

4. Permeability range

Property	FeNi (High Flux)	Sendust (Kool Mu)
Typical μ range	14 – 160	26 – 125
Temperature coeff. of μ	Small variation, grade-dependent	Stable, slight variation
Magnetostriction	Moderate	Very low (quiet)

Sendust has very low magnetostriction, which means less audible noise in PFC and resonant circuits. If the design is sensitive to acoustic noise, Sendust is usually preferred.

5. Temperature range

FeNi powder cores operate reliably from −40 °C to +180 °C with flat permeability behavior, suiting automotive (AEC-Q200) and outdoor energy applications. Sendust also covers a wide range but loses permeability faster at the high end. For under-hood or enclosed industrial designs, confirm the permeability curve at your maximum hot-spot temperature.

6. Cost

Sendust is the more economical of the two. FeNi alloy powder is more expensive per kilogram because of the nickel content. At high current, though, the FeNi core can be 30–40% smaller, so the total inductor cost can be comparable — and system-level savings (smaller PCB, fewer parallel parts, smaller EMI filter) can more than make up the difference.

Application decision tree

• High-current power inductor, tight size → FeNi (High Flux)
• PFC inductor at moderate current, cost-sensitive → Sendust
• EV charger, server POL, AI GPU VRM → FeNi
• EMI filter, low-noise design → Sendust
• Buck converter with heavy DC bias → FeNi
• Resonant circuit, noise-sensitive → Sendust

For a deeper comparison with MPP and ferrite, see FeNi vs MPP Powder Cores and Ferrite vs Iron Nickel Core. The IEC 63299 classification guide explains the standard material family codes.

YUTE Magnetics manufactures FeNi powder cores and custom inductors with IATF 16949 quality management, plus AEC-Q200 stress testing per part number on request. Send your inductance, current and frequency targets for a free technical evaluation — our engineers will recommend the right material and core size for your design.

Frequently Asked Questions

What is the difference between FeNi and Sendust powder cores?

FeNi (High Flux) offers Bs ≥1.5 T, roughly 40% higher saturation than Sendust at about 1.05 T. Sendust generally has lower core loss in the mid-frequency range (20–500 kHz) and costs less.

Which core should I choose for a PFC inductor?

At moderate current and where cost matters, Sendust is a common choice because of its lower loss and lower price. Where current is high and board space is constrained, FeNi allows a smaller core with better bias stability.

Is FeNi better than Sendust for high-current inductors?

For high current, yes in most cases: the higher saturation means the required inductance can be delivered in a smaller volume, and inductance holds up better under heavy DC bias. Sendust would need a larger core for the same duty.

Which material is quieter in operation?

Sendust has very low magnetostriction, so it produces less audible noise. Where acoustic noise is a concern, such as in resonant circuits, Sendust is usually the preferred choice.

How much does cost differ between FeNi and Sendust?

Sendust is the more economical material. FeNi costs more per kilogram because of its nickel content, though the smaller core size at high current can offset part of the difference in the finished component.