Re: [TCML] NST primaries

[David Dean <deano@xxxxxxxxxxxxxxxx>]

Hi

On Wednesday 04 June 2008 08:49:05 pm Mddeming@xxxxxxx wrote:
>  
> I think this will also double the secondary voltage which should toast it  
> instantly.
>  
It won't. 

Let us say the transformer uses 1 turn per volt (for the sake of simple 
arithmetic). As manufactured, the transformer has two independent primary 
windings designed for 120V. So each winding has 120 turns.  The primary 
windings are in parallel so each sees 120 volts across it. There are two 
independent secondaries, each with 7500 turns. The way the core is designed, 
primary-shunts-secondary, then primary-shunts secondary, it is like two 
separate transformers. Each primary winding drives its own secondary. So if 
you series the primaries and put in 240V you still have 120V seen across each 
primary, so still 7500V across each secondary.

Another way to look at it disregarding the unique core design, is that when 
the primaries are in parallel the current through the primaries is split 
between them, like a bifilar winding. The total effective turns is 120. The 
turns ratio (overall) is 120 to 15000. It is a step up transformer, so 
15000/120 = 125/1, and 125*120=15000.
Now if we series the primaries, all the current goes through both primaries, 
so we have in effect 240 turns. 15000/240 = 62.5/1, and 62.5*240=15000.

later
deano


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