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Toroids: Powdered Iron

Use the table below to calculate inductance and number of turns per the following formulas.

Toroidal inductor equation formula

Where:

L = inductance in µH

AL = µH per 100 turns

N = number of full turns

AL Values
  Mix Type
Size 26 3 15 1 2 7 6 10 12 17 0
T-12 n/a 60 50 48 20 18 17 12 7.5 7.5 3.0
T-16 145 61 55 44 22 n/a 19 13 8.0 8.0 3.0
T-20 180 76 55 52 27 24 22 16 10 10 3.5
T-25 235 100 85 70 34 29 27 19 12 12 4.5
T-30 325 140 93 85 43 37 36 25 16 16 6.0
T-37 275 120 90 80 40 32 30 25 15 15 4.9
T-44 360 180 160 105 52 46 42 33 18.5 18.5 6.5
T-50 320 175 135 100 49 43 40 31 18 18 6.4
T-68 420 195 180 115 57 52 47 32 21 21 7.5
T-80 450 180 170 115 55 50 45 32 22 22 8.5
T-94 590 248 200 160 84 n/a 70 58 32 n/a 10.6
T-106 900 450 345 325 135 133 116 n/a n/a n/a 19
T-130 785 3350 250 200 110 103 96 n/a n/a n/a 15
T-157 870 420 360 320 140 n/a 115 n/a n/a n/a n/a
T-184 1640 720 n/a 500 240 n/a 195 n/a n/a n/a n/a
T-200 895 425 n/a 250 120 105 100 n/a n/a n/a n/a

Iron Powder Magnetic Core Properties
Mix Color Material μ Temp

Stability

(ppm/°C)

f

(MHz)

Uses
26 Yellow/White Hydrogen Reduced 75 825 DC -1 EMI filters, DC chokes
3 Gray Carbonyl HP 35 370 0.05 - 0.50 Exc. stability, good Q at low freq.
15 Red/White Carbonyl GS6 25 190 0.10 - 2 Exc. stability, good Q
1 Blue Carbonyl C 20 280 0.50 - 5 Exc. stability, good Q at low freq.
2 Red Carbonyl E 10 95 2 -30 High Q
7 White Carbonyl TH 9 30 3 - 35 Similar to mix 2 and mix 6, exc. temp stability
6 Yellow Carbonyl SF 8 35 10 -50 Very good Q and temp. stability for 20-50 MHz
10 Black Powdered Iron W 6 150 30 - 100 Good Q and stability for 40-100 MHz
12 Green/White Synthetic Oxide 4 170 50 - 200 Good Q, moderate temp. stability
17 Blue/Yellow Carbonyl 4 50 40 - 180 Similar to mix 12, better temp. stability, Q drops about 10% above 50 MHz, 20% above 100 MHz
0 Tan Phenolic 1 0 100 - 300 L varies greatly with winding technique

Iron Powder Magnetic Core Dimensions
Size Color Dimensions (in)
O.D. I.D. Height
T-200-2 Red 2.00 1.25 0.55
T-94-2 Red 0.94 0.56 0.31
T-80-2 Red 0.80 0.50 0.25
T-68-2 Red 0.68 0.37 0.19
T-50-2 Red 0.50 0.30 0.19
T-37-2 Red 0.37 0.21 0.12
T-25-2 Red 0.25 0.12 0.09
T-12-2 Red 0.125 0.06 0.05
T-50-10 Black 0.50 0.30 0.19
T-37-10 Black 0.37 0.21 0.12
T-25-10 Black 0.25 0.12 0.09
T-12-10 Black 0.125 0.06 0.05
T-94-9 Yellow 0.94 0.56 0.31
T-80-6 Yellow 0.80 0.50 0.25
T-68-6 Yellow 0.68 0.37 0.19
T-50-6 Yellow 0.50 0.30 0.19
T-26-6 Yellow 0.25 0.12 0.09
T-12-6 Yellow 0.125 0.06 0.05

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