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PRIMARY??


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From:  Thomas McGahee [SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent:  Sunday, March 22, 1998 9:50 AM
To:  Tesla List
Cc:  mwise-at-sosis-dot-com
Subject:  Re: PRIMARY??


> 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,
Good question! Look at it this way: Yes, the 'extra' unused turns are
developing a voltage. In fact, several tens of KV most likely. But
since there is no 'loading' on these turns, there is no power 'loss'
(assuming you don't have any corona loss).

Taking it to the extreme, a Tesla coil can be made using an auto-
transformer style flat pancake coil. The output is normally the
center, by the way. Part of the coil acts as the primary, and the
rest acts as the secondary. In ***this*** case you **will** get
corona loss.

Bottom line: for most coilers the amount of 'loss' encountered due to
unused primary turns being in the circuit is so small that you can
safely ignore them in practice.

BTW, one reason why it is usually better to tap outward on the primary
is that if you tap inward (one connection at extreme outside), the
inner turns will have a high enough voltage to cause an arc to strike
from the primary to the secondary base.

Hope this helps.
Fr. Tom McGahee