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Yet another question about Balasting
Ok, first a little math
If Current = V/(2*Pi*F*L)
Then Inductance = V/(2*Pi*F*I)
So, for a 60 Hz system we have...
Current 120VAC 240VAC
Limit (mH) (mH)
1 318.3 636.6
2 159.2 318.3
3 106.1 212.2
4 79.6 159.2
5 63.7 127.3
6 53.1 106.1
7 45.5 90.9
8 39.8 79.6
9 35.4 70.7
10 31.8 63.7
11 28.9 57.9
12 26.5 53.1
13 24.5 49.0
14 22.7 45.5
15 21.2 42.4
16 19.9 39.8
17 18.7 37.4
18 17.7 35.4
19 16.8 33.5
20 15.9 31.8
21 15.2 30.3
22 14.5 28.9
23 13.8 27.7
24 13.3 26.5
25 12.7 25.5
26 12.2 24.5
27 11.8 23.6
28 11.4 22.7
29 11.0 22.0
30 10.6 21.2
31 10.3 20.5
32 9.9 19.9
33 9.6 19.3
34 9.4 18.7
35 9.1 18.2
36 8.8 17.7
37 8.6 17.2
38 8.4 16.8
39 8.2 16.3
40 8.0 15.9
(Boy! Can Excel *ever* be handy :)
Ok, now that we have the value in millihenrys (millihenries???)
to give us whatever current limit we want;
it's time to start building some inductors.
My question....
Where is a good (i.e. cheap) place to get EI cores to wind these on???
and would anyone happen to know the formula for an inductor wound on
one???
(the ones I've seen usually look more like sections of thick walled
cylinders than a perfect toroid, does that matter???)
Thanks,
Paul
I had a thought about building a series of inductors with current limits
of
1A, 2A, 4A, 8A, (& maybe 16A & 32A) and using relays to turn them on in
parallel
combinations to give me whatever limit I wanted up to 1A less than twice
the
highest value. Perhaps even using some logic controler so I could use
BCD
thumbwheel switches to "dial in" the value I wanted.