Powdered-Iron Toroidal-Cores
Magnetic properties
Inductance and Turns formula
The turns required for a given inductance or a inductance for a given number of turns can be calculated from:
N=100 √ L/AL or L=AL{N2/10.000}
Were N = number of turns;
L = desired inductance (μH)
AL = inductance index (μH per 100 turns)
| AL Values (μH 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 |
115 |
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
|
Magnetic Properties Iron Powder Cores
Most powdered-iron toroid-cores that radio amateurs use are manufactured by Micrometals, who uses paint to identity the material used in the core. The Micrometal color code can find in the table below.
|
Mix
|
Color
|
Material
|
μ
|
Temp stability
(ppm/0C)
|
f (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 lowe frequencies
|
|
15
|
red/white
|
carbonyl gs6
|
25
|
190
|
0,1 – 2
|
Excellent stability, good Q
|
|
1
|
bleu
|
carbonyl c
|
20
|
280
|
0,5 – 5
|
Similar to mix 3, but better stabillity
|
|
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 temp stabillity
|
|
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
|
bleu/yellow
|
carbonyl
|
4
|
50
|
40 – 180
|
Similar to Mix-12, better temp. stability, Q drops about 10% above 50 MHz, 20% above 100MHz
|
|
0
|
tan
|
phenolic
|
1
|
0
|
100 – 300
|
Inductance may vary greatly with winding technique
|