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PRIMARY??
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From: Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent: Sunday, March 22, 1998 5:59 AM
To: Tesla List
Subject: Re: PRIMARY??
Tesla List wrote:
>
> ----------
> From: Zuma [SMTP:mwise-at-sosis-dot-com]
> Sent: Saturday, March 21, 1998 9:51 PM
> To: tesla-at-pupman-dot-com
> Subject: PRIMARY??
>
> I was sitting here looking through my e-mail from the list and thought
> of a question about the primary. I have heard before to aleast leave an
> few extra turns for tuning purposes, but can there be to many turns?
> What I mean is that if you have a coil that tunes in at say 5 turns and
> your primary consists of 15 turns. Will having these 10 extra turns be
> lossy to the coil? It in a way seems like it might because it isn't
> concentrating to only those 5 turns. Take for instance this, your
> primary is tapped at turn 5, regardless of this tap I am assuming there
> is voltage still at the outer turn, so wouldn't this be some sort of a
> loss to the amount of energy being transfered? Is this a valid
> assumption?
>
> Chris Jones
Chris,
The problem with having too many turns is that the extra turns behave as
an autotransformer. The turns out from the tap will actually increase
the maximum voltage on the primary by the respective turns-ratio of the
total versus the used turns. If you're unly using a third of the
primary, you'll basically have 3X step-up of the primary voltage at the
end turn!
Since the grounded strikerail is tyupically only 1.5 - 2" above the
outermost turn, this can (and has :^( ) led to flashovers between the
outermost turn and ground due to the higher voltage. When I just
completed a primary for a 10" coil, I wanted to fire up my older 6"
secondary to try it out, since the 10" secondary was not yet complete.
This required tapping in at about turn 6 of a 17-turn primary. When the
sparks started flying I quickly began to get very hot, white arcs
between turn 17 and the strikrail easily jumping about 2". You tend to
remember the lessons you've learned the hard way - assuming you
survive... :^)
Safe coilin' to you, Chris!
-- Bert --