Powdered-Iron Toroid Cores: Magnetic Properties


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

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