RE: TC efficiency, was Math help...

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi John C., all,

On 16 Jul 01, at 7:36, Tesla list wrote:

> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-worldnet.att-dot-net>
> 
> 
> Bart -
> 
> You are correct I was refering to the "overall efficiency" of a Tesla coil.
> Refer to my post to John F.
> 
> I don't understand what you mean by "spark gap losses may offset any
> efficiency gain". The losses determine the amount of the efficiency.
> 
> Don't confuse power with energy. The the spark length vs input power
> equation is a power equation. The input power for a foot of spark can be
> considered an energy equation regardless of the amount of input power.
> 
> The input power for a foot of spark always is larger for larger coils
> compared to small coils. This is an indication that larger Tesla coils are
> less efficient than small coils. I think Tesla mentioned this in the CS
> Notes. The reason is that large coils have much heigher voltages than small
> coils and this increases the corona, etc, losses per unit of output/input.

If corona production is suppressed for the system in question (and it 
can be, although one might be driven to extreme measures to do it), 
there is one thing that always changes as a secondary gets larger - 
its capacitance. For a given shot of energy, that amounts to a drop 
in output voltage as the coil increases in size. You can make a coil 
develop any voltage you like bearing in mind that as voltage 
increases, at some point the coil will flashover its windings.

Regards,
Malcolm

> Note that coupling is not involved with efficiency, only with the
> Coefficient of Leakage which is an interesting magnetic circuit limitation
> for Tesla coils.
> 
> I agree we have a lot to learn about Tesla coils before we can design them
> with a minimum of guestimating.
> 
> John Couture
> 
> ---------------------------------
> 
> 
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Sunday, July 15, 2001 4:40 PM
> To: tesla-at-pupman-dot-com
> Subject: Re: TC efficiency, was Math help...
> 
> 
> Original poster: "Barton B. Anderson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>
> 
> John C.
> 
> Tesla list wrote:
> 
> > Original poster: "John H. Couture by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <couturejh-at-worldnet.att-dot-net>
> >
> > John F -
> >
> > A well known characteristic of Tesla coils is that the watts per foot of
> > spark increases as the TC gets larger. This means losses increase and
> > efficiency decreases as the TC is made larger. The range is about 200
> watts
> > per foot of spark for small coils to 2000 watts for large coils. This is
> > based on measurements that  coilers make every day. Have you made
> > measurements that would indicate the contrary?
> >
> > John Couture
> 
> This may be true in "overall" efficiency. I disagree with that this is a
> "well known characteristic" but we
> have discussed this over and over again on the list. Maybe well understood
> by only a select few (I don't put
> myself into that catagory). There are areas in larger systems that may be
> more efficient and areas less
> efficient. Although the transformer should be more efficient, the sparkgap
> losses probably offset any
> efficiency gain. This offset may be large or small based on gap designs,
> low to high inductive primary's,
> coupling, etc..
> 
> How much data is there really where losses are quantified across "main
> components" on big systems or small?
> Sure, there may be a few, but is there enough data on coils where we can
> make statements about large coils
> power per foot of spark increasing with coil size and relate "that" to
> large coils are more or less efficient?
> I would say yes, "if" we include that "typically" this occurs on larger
> systems because, with larger coils
> comes larger current feeds, enabling larger systems to simply add another
> megawatt to achieve longer
> sparklengths without consideration to efficiency in the design.
> 
> However, if we build and test a small and large system designed for peak
> efficiency in every possible
> aspect.... well, I don't think we have that information and couldn't make a
> definitive statement (although we
> could easily theorize).
> 
> Take care,
> Bart
> 
> 
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