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Re: [TCML] transformer theory questions

Hi Thomas,

My comments are interspersed with yours below...

--- On Sun, 9/20/09, Thomas Ryckmans <thomas.ryckmans@xxxxxxxxxx> wrote:

> From: Thomas Ryckmans <thomas.ryckmans@xxxxxxxxxx>
> Subject: [TCML] transformer theory questions
> To: tesla@xxxxxxxxxx
> Date: Sunday, September 20, 2009, 4:49 PM
> Hello,
> 
>  
> 
> I have general questions about transformer theory, and
> hopefully you'll be
> able to point me in the right direction. looking at
> textbooks, all
> transformers behave "ideally" so it is not of great use.

I disagree.  As an instructor of basic electronics, I find "ideal" components quite useful for teaching theory of operation.  If one can grasp ideal operation, it isn't much of a leap to comprehend real-world behavior.

> 
>  
> 
> How is the current output of a NST fixed?

This is well documented in the TCML archive should you require more detailed treatment of the subject.  Here's the condensed version:  The NST is a "shunted" transformer.  The shunts are small stacks of iron laminations physically wedged into the core windows between the primary and secondary coils.  The shunts deliberately introduce a large leakage inductance into the NST.  Leakage inductance is lines of magnetic flux originating in the primary coil that do not reach the secondary coil and is considered a form of inefficiency in most transformers.  However, in NSTs current limiting is more important than efficiency.  The core shunts partially short out the magnetic path between the NST primary and secondary, preventing some of the lines of flux from reaching the secondary.  The effect becomes more extreme as load current increases, resulting in a plateau at 30mA that cannot be exceeded, even if the NST is terminated into a short-circuit.

> 
>  
> 
> What is depotting - I understand the removal of tar etc,
> but why do it
> (sounds messy) and does it allow to change the output
> current?

Depotting itself doesn't increase the output of an NST.  Depotting merely gives you access to the shunts.  Removing some of the shunts will increase the output current.

> 
>  
> 
> What happens if you cut into the frame of a transformer,
> cutting the across
> the iron lamination?

I dunno for sure what will happen.  It will probably just ruin the NST.

> Many thanks
> 
>  
> 
> Thomas
> 
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>

Cheers,

Gregory R. Hunter


      

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