Powdered-Iron Toriod Cores
This is a long page containing 4 tables. The first two relate to magnetic properties. The second two relate to dimensions.
Inductance and Turns Formula
These formulas work if you have a table to use them with such as the example table below for 100 turns.
The turns required for a given inductance or inductance for a given number of turns can be calculated from:
N = 100 * SQRT( L / A(l) ) L = A(l) * ( N^2 / 10,000 )
N = number of turns, L = desired inductance (uH), A(l) = inductance index (uH per 100 turns).
A(l) Values (uH per 100 turns)
_____________________________MIX________________________
Size 26* 3 15 1 2 7 6 10 12 17 0
----- ---- ---- --- --- --- --- --- -- ---- ---- ----
T-12 na 60 50 48 20 18 17 12 7.5 7.5 3.0
T-16 145 61 55 44 22 na 19 13 8.0 8.0 3.0
T-20 180 76 65 52 27 24 22 16 10.0 10.0 3.5
T-25 235 100 85 70 34 29 27 19 12.0 12.0 4.5
T-30 325 140 93 85 43 37 36 25 16.0 16.0 6.0
T-37 275 120 90 80 40 32 30 25 15.0 15.0 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 18.0 18.0 6.4
T-68 420 195 180 115 57 52 47 32 21.0 21.0 7.5
T-80 450 180 170 160 55 50 45 32 22.0 22.0 8.5
T-94 590 248 200 160 84 na 70 58 32.0 na 10.6
T-106 900 450 345 325 135 133 116 na na na 19.0
T-130 785 350 250 200 110 103 96 na na na 15.0
T-157 870 420 360 320 140 na 115 na na na na
T-184 1640 720 na 500 240 na 195 na na na na
T-200 895 425 na 250 120 105 100 na na na na
*Mix-26 is ismilar to the older Mis-41, but can provide an extended frequency range.
Magnetic Properties of Iron Powder Cores
Temperature
Stability frequency
Mix Color Material u (ppm/deg C) (MHz) Notes
--- ------------ ---------------- -- ----------- ----------- -----------------
26 Yellow/White Hydrogen reduced 75 825 dc - 1 Used for EMI filters and dc chokes
3 Gray Carbonyl HP 35 370 0.05 - 0.50 Excellent stability, good Q for lower
frequencies
25 Red/White Carbonyl GS6 25 190 0.10 - 2 Excellent stability, good Q
1 Blue Carbonyl C 20 280 0.50 - 5 Similar to Mix-3, but better stability
2 Red Carbonyl E 10 95 2 - 30 High Q material
7 White Carbonyl TH 9 30 3 - 35 Similar to Mix-2 and Mix-6, but better
temperature 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 Inductance may vary greatly with winding
technique
**Phenolic is nearly an air core.
NOTE: Color codes hold only for cores manufactured by Micrometals.
Courtesy of Amidon Association and Micrometals.
Powdered-Iron Toroid Cores: Dimensions
Inductance and Turns Formula
The number of turns (N) necessary to obtain a specific inductance (L) can be calculated by
N = 100 * SQR( L / L(100) )
L = desired inductance in uH, L(100) = core inductance (uH per 100 turns from table below)
Inductance per 100 turns +/- 5% (all values in uH)
Size MIX-41 MIX-3 MIX-15 MIX-1 MIX-2 MIX-6 MIX-10 MIX-12
----- ------ ----- ------ ----- ----- ----- ------ ------
T-200 755 360 120 105
T-184 1640 720 240
T-157 970 420 140 115
T-130 785 330 250 200 110 96
T-106 900 405 330 280 135 116
T-94 590 248 160 84 70 58 32
T-80 450 180 170 115 55 45 34 22
T-68 420 195 180 115 57 47 32 21
T-50 320 175 135 100 50 40 31 18
T-37 240 110 90 80 42 30 25 15
T-25 200 100 85 70 34 27 19 13
T-12 90 60 48 24 19 12 8.5
Magnetic Properties Iron Powder Cores
Temperature Typical Optimum
Stability Frequency Frequency
Material Color Code Permeability (ppm/deg C) Range (Hz) Range (Hz)
-------- ---------- ------------ ----------- ----------- -----------
41' HA' Green u = 75 975 10k - 100k 20k - 50k
3' HP' Gray u = 35 370 20k - 2M 50k - 500k
15' GS6' Red/White u = 25 190 20k - 5M 500k - 1M
1' C' Blue u = 20 280 40k - 5M 1M - 2M
2' E' Red u = 10 95 200k - 30M 2M - 10M
6' SF' Yellow u = 8 35 2M - 50M 10M - 20M
10' W' Black u = 6 150 4M - 100M 20M - 40M
12' lrn-8' Green/White u = 3 170 10M - 200M 40M - 90M
0' Ph' Tan u = 1 - 50M - 300M 90M - 150M
Courtesy of Amidon Associaites.
Ferrite Toriod Cores
Number of Turns Formula
N = 1000 * SQR( L / A(l) )
N = number of turns, L = desired inductance in mH, A(l) = valur from table below.
Core 63/67-Mix 61-Mix 43-Mix 77 (72) Mix J (75) Mix
Size u = 40 u = 125 u = 850 u = 2000 u = 5000
------ --------- ------- ------- ----------- ----------
FT-23 7.9 24.8 188.0 396 980
FT-37 19.7 55.3 420.0 884 2196
FT-50 22.0 68.0 523.0 1100 2715
FT-82 22.4 73.3 557.0 1170 na
FT-114 25.4 79.3 603.0 1270 3170
Ferrite Magnetic Properties
Property Unit 63/67-Mix 61-Mix 43-Mix 77(72) Mix J(75) Mix
------------------- -------- --------- --------- --------- ---------- ----------
Initial perm. u(i) 40 125 850 2000 5000
Max perm. 125 450 3000 6000 8000
Saturation flux
density @ 10 oer Gauss 1850 2350 2750 4600 3900
Residual flux
density Gauss 750 1200 1200 1150 1250
Curie temp. deg C 450 350 130 200 140
Vol. resistivity ohm/cm 1E8 1E8 1E5 1E2 5E2
Resonant circuit
frequency MHz 15-25 0.2-10 0.01-1 0.001-1 0.001-1
Specific gravity 4.7 4.7 4.5 4.8 4.8
Loss factor 1/ 110E-6 32E-6 120E-6 4.5E-6 15E-6
Q * u(i) @25 MHz @2.5 MHz @1 MHz @0.1 MHz @0.1 MHz
Coercive force Oer 2.40 1.60 0.30 0.22 0.16
Temp. Coef. of %/deg C
initial perm. (20-70 C) 0.10 0.15 1.0 0.60 0.90
NOTE: 1E6 is shorthand for 1 * 10^6 (one times ten raised to the 6th power).
Ferrite Toroids Physical Properties
Core
Size OD ID Height A(e) I(e) V(e) A(s) A(w)
------ ------ ------ ------ -------- -------- -------- -------- ---------
FT-23 0.230 0.120 0.060 0.00330 0.529 0.00174 0.1264 0.01121
FT-37 0.375 0.187 0.125 0.01175 0.846 0.00994 0.3860 0.02750
FT-50 0.500 0.281 0.188 0.02060 1.190 0.02450 0.7300 0.06200
FT-82 0.825 0.520 0.250 0.03810 2.070 0.07890 1.7000 0.21200
FT-114 1.142 0.750 0.295 0.05810 2.920 0.16950 2.9200 0.43900
OD - Outer diameter (inches) A(e) - Effective magnetic cross-sectional are (in^2)
ID - Inner diameter (inches) I(e) - Effective magnetic path length (inches)
Height - Height (inches) V(e) - Effective magnetic volume (in^2)
A(s) - Survace area exposed for cooling (in^2)
A(w) - Total window area (in^2)
Courtesy of Amidon Association