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# ballast Inductor Choke coil (fwd)

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From:  Mad Coiler [SMTP:tesla_coiler-at-hotmail-dot-com]
Sent:  Friday, April 03, 1998 10:13 AM
To:  tesla-at-pupman-dot-com
Subject:  Re: ballast Inductor Choke coil (fwd)

>----------
>From:  Alfred A. Skrocki [SMTP:alfred.skrocki-at-cybernetworking-dot-com]
>Sent:  Thursday, April 02, 1998 6:39 AM
>To:  Tesla List
>Subject:  Re: ballast Inductor Choke coil (fwd)
>
>On Tue, 31 Mar 1998 18:47:49 EST Erik Schulz
><ESchulz531-at-aol-dot-com> wrote;
>
>> Matt,
>>       When an inductor is placed in series with an AC source it
causes
>> resistance governed by this equation.  R = 2 * Pi * f * L
>>
>> So for a transformer that uses about 1kw you would need 14.4 ohms
with a 120
>> volt wall socket, so the inductance should be about 0.0382 H,
>
>Up to here everything checks out OK.
>
>> so on a 12 in cylinder with a 6 inch diameter you would need about
780 turns
>> with air as the core.
>
>NO WAY! The standard equation for calculating the number of turns need
on a
>helical inductor is;
>

Alfred,

You defenitaly prooved your point here, but I put the figures into a
computer program I have that calculates values for helical coils,
entering 38200uH, 3" radius, and 12" winding length and I got 789.89
turns. Is there something wrong with this program?

>    N = SQRT (L * ((9 * R) + (10 * H))/R * R)
>
>    N = Number of turns needed.
>    L = inductance in microhenrys.
>    R = radius (inches).
>    H = height (inches).
>
>Now in your earlier calculation you determined that you wanted a 0.0382
>Henry inductance to convert this into microhenrys you would divide the
>value in Henrys by 0.000001 thus giving; 38200 microhenrys! Now pluging
>that into the above equation along with your cylinders measurements
gives;
>
>    N = SQRT (38200 * ((9 * 3) + (10 * 12))/3 * 3)
>
>Then:
>
>    N = 1475 turns would be required
>
>A far cry greater than 780 turns! Now dividing 12 by 1475 gives 0.008
>inches or 8 mils for the maximum possible thickness of the wire
(including
>the insulation) which would be #33 gauge. Now taking the diameter of
that
>cylinder; 12 and multiplying this by pi to get the length of one turn
>yields; 37.7 inches, Which when multiplied by the 1475 turns yields;
>155607.5 inches or apx. 4634 feet! Now the resistance per 1000 fet of
#33
>wire is; 205.7 ohms, multiplying this by 4.634 gives; 953.2 ohms D.C!
The
>D.C. resistance of this coil is 66 times greater than it's impedance.
In
>short it is impractical to make a single layer air core with this high
an
>impedance! It would be neccessary to use a multilayer core, preferable
with
>an iron core to get the number of turns down far enough so you could us
a
>wire such that it's D.C. resistance was significantly smaller than it's
>impedance, otherwise it will never pass the needed current!
>
>>  I don't know how to figure out the internal resistance of the
transformer.
>
>Actually you did that in the begining of your calculation! I'll use
your
>1 Kilowatt transform. 1000/120 = 8.33 amps drawn by the transformers
>primary. Then since Z = E/I we have 120/8.33 = 14.4 ohms impedance. If
>you say, wanted to current limit this transformer to 500 watts you
would
>need to put another 14.4 ohms impedance in series with the transformer,
in
>other words you would need a 0.0382 Henry choke in series with the
>transformer.
>
>                                       Sincerely
>
>                                        \\\|///
>                                      \\  ~ ~  //
>                                       (  -at- -at-  )
>                                -----o00o-(_)-o00o-----
>                                   Alfred A. Skrocki
>                               Alfred.Skrocki.Sr-at-JUNO-dot-com
>                           alfred.skrocki-at-cybernetworking-dot-com
>                      Visit my Do-It-Yourself Aquarium WEB page at;
>                       http://www.geocities-dot-com/CapeCanaveral/6251
>                                     .ooo0   0ooo.
>                                -----(   )---(   )-----
>                                      \ (     ) /
>                                       \_)   (_/
>
>
>
>
>

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