Re: How should we measure coil efficiency

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: How should we measure coil efficiency
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 23 Jul 1997 12:47:24 -0500
Approved: tesla-at-stic-dot-net

From: 	John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: 	Wednesday, July 23, 1997 1:58 AM
To: 	Tesla List
Subject: 	Re: How should we measure coil efficiency

At 08:10 AM 7/22/97 +0000, you wrote:
>
>From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
>Sent: 	Monday, July 21, 1997 11:02 AM
>To: 	tesla-at-pupman-dot-com
>Subject: 	Re: How should we measure coil efficiency
>
------------------------------------------------

 John, Greg, All -

 The Tesla coil efficiency is found with the following equation:

         % eff = (energy out/energy in) x 100

  Note that energy equals watts x time. Measuring the "energy in" is
possible by measuring the watts x time at the input. Measuring the "energy
out" by using sparks appears to be impossible from an engineering
standpoint. However, measuring "energy out" is possible using a load that
gives you watts x time. The easiest way to do this is with an incandescent
lamp. These devices can be easily calibrated in WATTS by using a light meter.

  I show how I tested a 7500 volt, 30 ma TC for efficiency in the Tesla Coil
Construction Guide. Also shown is a JHCTES computer program printout for
this coil. The JHCTES computes the % efficiency in a different manner but
comes up with a close agreement with the test.

  This is a very simple and accurate test and can be easily implemented by
any coiler and verified by the JHCTES program.

  John Couture

----------------------------------------------------

>>snip>
>> GOODNESS = (spark length to grounded terminal)  vs. (Energy in Cpri) X BPS
> 
>Greg,  
>
>Are you refering to a steady, connected spark to ground, or occasional hits?
>
>My concern about steady sparks to ground is that they may not be truly
>representative of the normal free air (or occasional to ground)
>spark length performance.  Malcolm's recent work at various 
>break-rates suggests this...if I'm understanding the
>conclusions of his findings.  In other words, two different TCs may give 
>indentical steady spark lengths to ground, but very different free air 
>spark lengths, (different than each other).  (free air length, same as
>occasional hits to ground length).
>
>Break-rate is tricky, the way in which it affects spark length and
>brightness seems poorly understood, since it is so dependent on 
>ionization effects in the air.  Break-rate seems to affect the relationship
>between "controlled" and free air sparks.
>
>Comments welcomed,
>
>John Freau
>   
>> This seems to be the most interesting TC figure of merit, since it measures
>> how effective the coil is at building arc bridges with the energy that is
>> delivered to its primary.  Long arcs seem to be the primary objective when
>> building TC's, so the art is obviously in making the longest arc with a
>> given amount of primary energy delivery.
> 
>> The above figure of merit is also easy to measure -- all that is required
>> is a tape measure and a voltmeter.
> 
>> -GL
>  >>
>
>
>
>