Wire Gauge Tables Appendix C: Core Specifications Reference specifications for magnetic cores commonly used in VIC choke design. Includes ferrite toroids, iron powder cores, and E-cores. Core Material Overview Material Type μᵣ Range Frequency Range Best For MnZn Ferrite 800-10,000 1 kHz - 2 MHz High L, moderate f NiZn Ferrite 15-1,500 500 kHz - 100 MHz High frequency Iron Powder 8-100 10 kHz - 10 MHz High current, low cost MPP (Molypermalloy) 14-550 DC - 1 MHz Low loss, stable Kool Mµ 26-125 DC - 500 kHz High current, moderate loss Air Core 1 Any No saturation, linear Common Ferrite Materials MnZn Ferrite Materials Material μᵢ B sat (mT) Frequency Notes Fair-Rite 77 2000 480 <1 MHz General purpose, high μ Fair-Rite 78 2300 480 <500 kHz Very high μ TDK N87 2200 490 <500 kHz Popular, low loss TDK N97 2300 410 <300 kHz Very low loss Ferroxcube 3C90 2300 470 <200 kHz Low loss at high B Ferroxcube 3F3 2000 440 <500 kHz Higher frequency Iron Powder Core Mix Chart Iron powder cores (Micrometals/Amidon) are identified by color code: Mix Color μᵣ Frequency Range Application -26 Yellow/White 75 DC - 1 MHz EMI/RFI filters -2 Red/Clear 10 250 kHz - 10 MHz RF, resonant circuits -6 Yellow/Clear 8.5 3 - 40 MHz Higher frequency -1 Blue/Clear 20 500 kHz - 5 MHz Medium frequency -3 Gray/Clear 35 50 kHz - 500 kHz Medium μ, low f -52 Green/Blue 75 DC - 200 kHz High μ, DC bias Common Toroid Sizes FT (Ferrite Toroid) Series Size OD (mm) ID (mm) H (mm) Aₗ (77 mat) Aₗ (43 mat) FT-37 9.5 4.7 3.2 884 440 FT-50 12.7 7.1 4.8 1140 570 FT-82 21.0 13.0 6.4 2170 557 FT-114 29.0 19.0 7.5 2640 603 FT-140 35.5 23.0 12.7 3170 885 FT-240 61.0 35.5 12.7 4820 1075 Aₗ values in nH/turn². Highlighted sizes are commonly used for VIC chokes. T (Iron Powder Toroid) Series Size OD (mm) ID (mm) H (mm) Aₗ (-2 mix) Aₗ (-26 mix) T-37 9.5 4.9 3.2 4.0 27 T-50 12.7 7.7 4.8 4.9 33 T-68 17.5 9.4 4.8 5.7 38 T-80 20.2 12.6 6.4 8.5 55 T-94 24.0 14.5 7.9 8.4 70 T-106 26.9 14.0 11.1 13.5 90 T-130 33.0 19.7 11.1 11.0 96 T-200 50.8 31.8 14.0 12.0 120 Inductance Calculations Using Aₗ Value: L (nH) = Aₗ × N² N = √(L / Aₗ) Example: Want L = 10 mH = 10,000,000 nH Using FT-240-77 (Aₗ = 4820 nH/turn²) N = √(10,000,000 / 4820) = 45.6 turns Use 46 turns for L ≈ 10.2 mH Saturation Considerations Saturation Flux Density (B sat ): Material Type B sat (mT) MnZn Ferrite 400-500 NiZn Ferrite 250-350 Iron Powder 800-1000 MPP 750 Calculating Peak Flux: B = (V × t) / (N × A e ) Where A e is effective core area. Keep B < 0.5 × B sat for linear operation. Temperature Effects Material Curie Temp (°C) Max Operating (°C) μ vs. Temp MnZn Ferrite 200-250 100-120 Peaks near 80°C, then drops NiZn Ferrite 300-500 150 Relatively stable Iron Powder 770 (iron) 125 (coating limited) Stable Core Selection Guide for VIC For Primary Choke (L1): Moderate L (1-50 mH typical) Moderate current handling Consider: FT-82-77, FT-114-77, T-106-26 For Secondary Choke (L2): May need higher L (10-100 mH) for high Q Lower current typically Consider: FT-140-77, FT-240-77 For High Frequency (>100 kHz): Use lower-μ materials to maintain SRF margin Consider: Iron powder -2 or -6 mix, NiZn ferrite Quick Reference: Turns Calculation Desired L FT-82-77 FT-240-77 T-106-26 1 mH 21 turns 14 turns 105 turns 5 mH 48 turns 32 turns 236 turns 10 mH 68 turns 46 turns 333 turns 25 mH 107 turns 72 turns 527 turns 50 mH 152 turns 102 turns 745 turns Approximate values. Verify with actual Aₗ from manufacturer datasheet.