# [TCML] Dr. Resonance inductors - 1/16th of an inch?

Stephen Hiscock stephenhiscock at yahoo.com
Fri Mar 6 02:02:00 MST 2009

```I think people might be possibly confusing the way they calculate the
inductance of a coil.

Large inductances are NOT hard to make - and certainly don't need to be
as big as a house!!!!!
or are we talking about stacking large amounts of these?

I believe inductance is calculated by
L= (d^2 * n^2)/(18*d+40*l)  (MicroHenries)
where:
L is inductance in micro Henrys,
d is coil diameter in inches,
l  is coil length in inches, and
n is number of turns.

so 25 inch diameter
length of 50 inches
and number of turns 2000
= 1,020,000uH
or 1.02 HENRIES
Which is physically quite big! - but so are tesla coils and no-one seems
to care?!?!

but if wound fairly compact they can be made smaller with more turms

eg
15 inch diameter
and 15 inch length
and 2000 turns gives
1,03 Henries
(but I guess this might not handle high voltage)

or 5 x 5 x 3500 turns = 1 Henry

or 1x 1 x 8000 turns = 1 Henry!!!
or 1/16th x 1/16th x 30000 turns = 1 Henry!!!!
does turns per volt matter?? -

I'm sure you get the point  - it depends on the dimensions and number of
turns - with the diameter or turns being the dominant factors
These numbers are NOT unusual -
Perhaps people are confusing Capacitance for inductance???
Now a 1 farad HIGH voltage capacitor would be quite large

Regards
Stephen

Jim Mora wrote:
> Hi All,
>
> It may be reasonable to assume that DC is confusing the 1mh air core choke
> or he has a hugh Marx generator much taller than his building!
>
> Respectfully,
> Jim Mora
>
> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On Behalf
> Of Lau, Gary
> Sent: Thursday, March 05, 2009 4:28 PM
> To: Tesla Coil Mailing List
> Subject: RE: [TCML] Dr. Resonance inductors
>
> Assuming a single-layer close-wound air core solenoid made from 30AWG magnet
> wire, a 1H inductor would be huge!  12.33" diameter x 36" long.
>
> I'll preface this by stating that I know very little about Marx generator
> construction.  But it seems to me that the inductors would need to support
> only the charging current of the caps by the PSU.  So if you're using a
> rectified 15/30 NST, 30 mA is the most that the inductors would need to
> support.  The discharge current of the erected circuit travels only through
> the gaps and caps - not the inductors.
>
>  The inductance requirement in a Marx generator is less clear, but as the
> erected pulse duration of a Marx generator is extremely brief, 1H seems WAY
> larger than necessary.  A little bit of Googling finds typical inductance
> values between .5-1.0 milliHenry.
>
> Regards, Gary Lau
> MA, USA
>
>
>> -----Original Message-----
>> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
>> Behalf Of Quarkster
>> Sent: Thursday, March 05, 2009 5:14 PM
>> To: Tesla Coil Mailing List
>> Subject: Re: [TCML] Dr. Resonance inductors
>>
>> DC -
>>
>> You are not implying that your stock of 1H air-core inductors are stored
>>
> outdoors
>
>> under a snow bank, are you??
>>
>> Would it be possible for one of your employees at Resonance Research
>>
> to provide
>
>> a photo of one of these very interesting inductors so we all don't have to
>>
> wait for
>
>> spring to arrive in Wisconsin?
>>
>> In the meantime (since these inductors have generated so much interest &
>> discussion), could you just share some details of their design &
>>
> construction?
>
>> Like -
>> 1. Air insulated, or oil insulated?
>> 2. Approximate physical dimensions?
>> 3. RMS current rating?
>> 4. Approximate weight?
>>
>>
> the top-
>
>> level specifications you would provide to a prospective customer.
>>
>> Regards,
>> Herr Zapp
>>
>>
>> --- On Thu, 3/5/09, DC Cox <resonance at wildblue.net> wrote:
>>
>> From: DC Cox <resonance at wildblue.net>
>> Subject: Re: [TCML] Dr. Resonance inductors
>> To: "Tesla Coil Mailing List" <tesla at pupman.com>
>> Date: Thursday, March 5, 2009, 9:20 AM
>>
>> I can't post a photo until I return to WI shop as they are in frozen
>>
> tundra
>
>> Wisconsin.  I'm in Tucson for the winter.
>>
>> I've used them in 3 Marx gens so far, and they work excellent.  Inductors
>> and resistors work the same in this circuit.
>>
>> DC
>>
>>
>>
>>
>>
>> On Wed, Mar 4, 2009 at 7:26 PM, Jim Mora <wavetuner at gmail.com> wrote:
>>
>>
>>> Hi Dc, List,
>>>
>>>
>>>
>>> I would very much like to see the construction of a 1H air core
>>>
> inductor.
>
>> I
>>
>>> plan to build a Marx Generator in the future. I know there are
>>>
>
>>> to
>>> using an inductor rather than a resistor in the stages besides prices.
>>>
> Can
>
>>> you post a picture and comment on the construction?
>>>
>>>
>>>
>>> Thanks,
>>>
>>>
>>>
>>> Jim Mora
>>>
>>> _______________________________________________
>>> Tesla mailing list
>>> Tesla at www.pupman.com
>>> http://www.pupman.com/mailman/listinfo/tesla
>>>
>>>
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>>
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