Re: ignition coil

From: 	Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Reply To: 	alfred.skrocki-at-cybernetworking-dot-com
Sent: 	Monday, July 21, 1997 5:44 PM
To: 	Tesla List
Subject: 	Re: ignition coil

On Monday, July 21, 1997 4:45 PM Malcolm Watts
[SMTP:MALCOLM-at-directorate.wnp.ac.nz] wrote;

> OK, how does it work? It works by storing energy in the core via the 
> primary and releasing it in both primary and secondary when the power 
> supply is cut off from the primary. 
> (1) How to maximise core energy? Since E = 0.5LI^2 and L is fixed, 
> you must get I as high as the primary winding can stand. Since I is 
> limited by Vapplied/Rwinding, the more V applied, the more I.  BUT,
> applying V to an inductance means it takes time for I to build up to 
> the resistance limited value. So dwell time must be set long enough.
> The longer the dwell, the slower the breaks have to be if core energy 
> is to be maximised.
> (2) How to get _all_ energy from the core to the secondary? Not easy.
> You have to break the supply from the primary without a spark across 
> the break contacts. Fast parting contacts are the order of the day.
> You can slow the rate of rise of core energy release by putting a 
> small capacitor across the contacts, the ideal being that the 
> contacts part company faster than the voltage across them rises.

Malcolm, I find nothing wrong with what you said except that it 
ignores one of Michael Faradays most important observations, namely
that the faster that the current is cut off from an inductor the 
faster the magnetic field collapses and the higher the induced 
voltage. It was to this end that Tesla started out with a mercury 
turbine interuptor for his initial H.V. generators and it was what 
lead Tesla to the design of the Tesla coil itself.


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