# Re: 60 vs. 30 ma

```Subject:  Re: 60 vs. 30 ma
Date:   Mon, 9 Jun 1997 03:52:10 +0000
From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
To:  Tesla List <tesla-at-pupman-dot-com>

At 12:47 AM 6/8/97 +0000, you wrote:
>Subject:  60 vs. 30 ma
>  Date:  Sat, 07 Jun 1997 15:58:21 -0500
>  From:  Tedd Payne <tpayne-at-netnitco-dot-net>
>    To:  Tesla List <tesla-at-pupman-dot-com>
>
>
>Thanks to those who replied.  Maybe I could have asked my question more
>clearly, so I'll try again.
>
>If I have a well-operating coil using a 12KV/30ma neon transformer, and
>I replace that transformer with a 12KV/60ma transformer:
>
>1.  To take best advantage of the 60ma, should I change the torroid size
>and/or change the primary tap location?  (assume the .005uF cap value
>won't change)
>
>I think I read that by using a larger torroid, a smaller cap could be
>used.  Therefore, if I use a 60ma transformer (which would normally call
>for about a .01 cap), I could get away with using the original .005 cap
>by using a larger torroid.  Is that correct?
>
>2. After changing the torroid size and/or primary tap, what increase in
>spark length should I expect as a result of moving up to 60ma?
>
>3.  If I changed only the primary tap location (if that would help) and
>did NOT change the torroid size, what increase in spark length should I
>expect as a result of moving up to 60ma?
>
>Thanks again,
>
>Tedd
>
>-------------------------------------------------------

Tedd -

The output (spark length) of a Tesla coil is based on the folowing
equation:

Output = Input minus Losses

It looks simple but isn't. However, this equation is the reason that
there
is sometimes little increase in spark length when the input power is
increased. Increasing the power will begin to increase the secondary
voltage
for a certain size of coil. When the sec voltage increases the losses
increase which tend to limit the increase in spark length. A point is
soon
reached where the losses are great enough to prevent the spark from
increasing at all. This generally results in the secondary sparking
across
the windings.

The reason I say it is not simple is because of the difficulty of
determining the increase in losses in the secondary circuit when the
input
power is increased. There are many ways to prevent losses in Tesla
coils.
Increase the size of the secondary wire, increase the insulation, etc.
In
the primary circuit increase the wiring, use a capacitor with less high
voltage losses, change the operating spark gap to a more efficient one,
etc.

What I am saying is to build a Tesla coil for 60 ma and use it with 30
ma.
When you get around to use it with 60 ma you will find the TC produces a
big
increase in spark length. The losses will be less than if you start with
a
30 ma coil.

Use a smaller toroid for the 30 ma and a larger toroid for the 60 ma.
The
primary should have enough turns to tune with either toroid.

There are several TC computer programs including the JHCTES program
that
are available to make the job easier. The JHCTES program will give you
the
toroid sizes and the primary turns you need. And much more, 46
parameters,
all in tune. In fact you can solve dozens of similar problems with this
program.

John Couture

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