Re: Math help...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

John,

As Ed points out, energy transfer in magnetic circuits where ferromagnetics
are involved are never lossless. However, John is correct for the typical
air core transformer used in a 2 coil TC. 

The example I was discussing compared the initial energy residing in the
tank cap at the instant the main gap fired versus the maximum energy in the
secondary at the end of the first energy transfer cycle. This was the
condition that Malcolm described (if I recall, this was done quite some
time back...). But if you don't directly measure the secondary voltage, how
can this be accomplished?? 

The measurement was done by:
1. Using a "magic" value for coupling (so that both the voltage and current
simultaneously hit zero upon completion of an energy transfer
2. Preventing breakout from the toroid even at peak secondary voltage
3. Permitting the peak secondary energy to transfer back into the primary
circuit (easy, since it's virtually impossible to quench the gap under
these conditions)
4. We then measure the primary capacitor voltage once the secondary's
energy has completely transferred back into the primary capacitor.

We actually measure the primary tank cap voltage before and after TWO
energy transfers. We can then back compute the energy that must have been
transferred to the secondary during a single primary-to-secondary energy
transfer. Under these conditions, it was determined that you could transfer
over 90% of the original tank energy to the secondary. Once it was there,
we can either dissipate part of it as streamers (desirable case) or return
most of it back to the primary (the case we measured). 

This does not take into effect losses in the charging circuit, and we have
purposely avoided losses from leaders/streamers. It does not address
scaling. However, anything that reduces main gap losses and secondary
losses will improve the primary-secondary transfer efficiency. High Z
primaries and lower operating frequencies (i.e., John Freau's guidelines
for efficient coil design) should apply...

Hope this explains the situation...

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-worldnet.att-dot-net>
> 
> Bert -
> 
> I agree with your excellent comments below, however, I believe it should be
> pointed out that the energy transfer in all magnetic circuits is 100%
> because there are no losses in magnetic circuits. Electric losses are only
> in electric circuits and the efficiency is the ratio of output/input. This
> means that when reffering to electrical efficiency the input and output
> calcs should be shown. This can be a difficult task when talking about Tesla
> coils.
> 
> I understand the voltage can be used to find the joules (energy) in the
> primary capacitor but how do you determine the energy in the secondary
> circuit when the secondary voltage of an operating TC is an unknown? I
> avoided this problem by using a light bulb for the secondary load in my
> test.
> 
> When we say the TC efficiency can be about 90/95% what are the input and
> output conditions? Coilers talk about TC efficiencies but I have never seen
> any published input/output calcs. In my TC Construction Guide page 14-4 I
> show a simple efficiency test I made with a small TC and the input/output
> calcs were shown. Have any other coilers made these tests? The test showed
> an overall efficiency of 56%. Larger coils have efficiencies much lower.
> What are the input and output calcs for the 90 to 95% efficiencies? How do
> they relate to the overall efficiency? How do these 90/95% efficiencies vary
> with TC size?
> 
> John Couture
> 
> ----------------------------
> 
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Sunday, July 08, 2001 9:02 PM
> To: tesla-at-pupman-dot-com
> Subject: Re: Math help...
> 
> Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <bert.hickman-at-aquila-dot-net>
> 
> Josh and all,
> 
> That's an excellent question, Josh - and it goes to show that very few
> things are truly simple in coiling... :^)
> 
> Malcolm is correct. Previous experiments have measured primary tank
> capacitor voltage during a complete primary-secondary-primary energy
> transfer cycle. These have shown that the efficiency of the first
> primary-to-secondary transfer (from an initially charged tank capacitor to
> a fully resonating secondary) can indeed exceed 90%. However, this makes no
> statement regarding how efficiently we were able to charge the tank cap
> from the mains supply in the first place. For that, we need to talk a bit
> more about capacitor charging circuits...
> 
> -------------------   snip