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Re: How to rise the secondary? (fwd)



---------- Forwarded message ----------
Date: Sun, 12 Jul 1998 06:56:41 -0700 (PDT)
From: gweaver <gweaver-at-earthlink-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: How to rise the secondary?

I think your right under perfect conditions but I don't think perfect
conditions exist. I know they don't in Tessessee. 

I build most of my coils in the winter when the air is cold and dry.  I have
designed some primary coils to be a little tight on the inside turn so I can
cut it off 1/4 turn at a time to find best coupling without having to raise
the secondary coil up.  

If you change something in the circuit, like the top load it changes the
coupling. If you change the capacitors, spark gap, chokes, power supply
voltage or anything in the circuit it changes the coupling.  Once you get
the perfectly designed Tesla Coil you can't change anything in the circuit.
I guess thats OK if you don't like to experement with your TC.  I thing
experement is what makes coiling fun.

I have 2 coils I keep set up all the time on the work bench, 4" 750 watt
coil and a 6" 1350 watt coil.  I tweaked them both out for best performance
in the cold dry winter air.  I have found that in the spring when the
weather gets a little warmer and the humidity is very high from all the rain
we have here I have no choice but to raise both of the secondary coils up to
stop arc over between the primary and secondary coils.  I have to raise the
6" coil 2" to stop arc over running the same power I did in the winter.
Raising the coil 2" reduces the output a little but running the coil at low
power to stop arc over reduces the output even more.

I think many of the people on the TC list may not have the humidity problems
I have living here in Tessessee.  We had non stop rain this year from the
last week of Feb. to the end of June. 4 months of non stop rain and maybe 4
or 5 days of the 4 months it didn't rain.  I should get into the umbrella
business.

If I could put a Tesla Coil in a large tank of high voltage oil it would be
very helpful to me. 

I don't use any test equipment, formulas or computer programs to make
coupling adjustment with and don't think its necessary to have any.  Makes
no difference what the test equipment or formulas say, the number one goal
is long discharge sparks. I move the secondary coil 1/2" at a time and
measure the discharge sparks to a target at low power, then fine tune by
moving the coil 1/4" then 1/8" at a time. Then I turn up the power and see
what happens.  Naturally if the power input is too much for the size coil I
am running it will arc over between the primary secondary coils.  You can't
run a 4" coil on 10KW, you need a larger coil. 

Make it simple and make it work.

Gary Weaver






>>   To All -
>>
>>   Why are coilers building Tesla coils and raising the secondary to make
>> them work properly? Raising the secondary of a properly designed and tuned
>> coil only reduces the output. Why use a faulty design of excessive
>> overcoupling then try to correct it by raising the secondary?
>>
>>   If a proper pri/sec clearance is maintained to prevent flashovers and the
>> coil properly tuned raising the secondary is unnecessary. Tweaking is part
>> of the tuning process and not necessary for coupling selection with a
>> correct design. With a properly designed TC the quenching adjustments relate
>> only to the primary circuit. Quenching always occurs after the first
>> transfer when the secondary circuit has almost zero energy and has no effect
>> on the primary circuit.
>>
>>   Critical coupling is the same for Tesla coils as it is for any dual
>> coupled RCL system. If this condition can be determined at the time of
>> design the correct amount of overcoupling can be determined and excess
>> overcoupling avoided. It does not make engineering sense to deliberately and
>> incorrectly design a coil with excessive overcoupling and then try to
>> correct it by raising the secondary.
>>
>>   I have studied and researched this problem with over a dozen coils. My
>> conclusion was that raising the secondary was not necessary with a properly
>> designed TC. In fact a TC that requires raising the secondary can never be
>> adjusted to produce optimum output. This is because moving the secondary
>> away from the primary will reduce the output. I have not solved the problem
>> of finding the exact coupling for a particular TC. However, coupling is not
>> critical as it does not affect the amount of energy transferred. Only
>> sufficient pri/sec clearance is required to prevent sparkovers. I agree more
>> research is needed.
>>
>>   John Couture
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