Material families
| Material | μᵢ (initial) | Frequency range | Saturation | Notes |
|---|---|---|---|---|
| MnZn ferrite | 1 000 – 15 000 | 10 kHz – 2 MHz | Sharp (0.3–0.5 T) | Power, transformers |
| NiZn ferrite | 10 – 1 500 | 1 – 500 MHz | Sharp (0.2–0.4 T) | RF chokes, EMI |
| Powdered iron (Fe) | 10 – 100 | DC – 5 MHz | Gradual (1.0+ T) | Switchers, chokes |
| Kool Mu (Fe-Si-Al) | 26 – 125 | < 1 MHz | Gradual | DC-tolerant |
| MPP (Moly Permalloy) | 14 – 550 | < 1 MHz | Gradual | High-quality DC inductors |
| HighFlux (Ni-Fe) | 14 – 160 | < 1 MHz | ~1.5 T | High saturation |
| Nanocrystalline | 10 000 – 200 000 | 50 Hz – 200 kHz | ~1.2 T | Common-mode chokes |
| Amorphous | > 100 000 | < 100 kHz | ~1.5 T | Precision CT, filter chokes |
| Air core | 1 | RF (MHz – GHz) | None | Highest Q at high f |
Picking a core
- Power inductor (buck/boost, ≤ 500 kHz): powdered iron or Kool Mu — soft saturation.
- Transformer for SMPS: MnZn ferrite (N87, 3C94, PC40) for 20–500 kHz.
- EMI / common-mode choke: NiZn ferrite or nanocrystalline for high-frequency blocking.
- RF: air-core or NiZn for lowest loss at high frequency.
- Current sensing / linearity: MPP or Kool Mu — small μ drop at high I.
Loss at frequency
- Loss = hysteresis (per cycle) + eddy currents (per f²) + residual.
- Loss rises rapidly above each material's recommended operating frequency.
- Core loss curves provided in datasheets at specified B and f — check before committing.
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