[TCML] Homebuilt Transformer - Can you add shunts?

[bartb]

Hi Phil,

It shouldn't matter if you have a single gap in the path or several. The 
affect of gap distance however will be additive. In Richie's Ballast, 
you can see the top core and the hard polystyrene shims he used for the 
gap. These shims are across both sides.
http://www.richieburnett.co.uk/parts2.html#ballast

For the UU's, you can add metallic shims in the center U's and then 
polystyrene the outer U's. This would probably help adjustment. You 
could also metallic shim one outer U and the center U's, then only 
polystyrene one outer U for the actual *gap*. I think you have some 
options here that might be worth playing with unless you can think of a 
decent means of adding shunts, but as the core is U shaped, that might 
be difficult to do. I think with the gap technique, you would have no 
need to force the secondary onto the outer U's. It could be done, but it 
would be nice if center tap wasn't necessary (as you could ground one 
side of the output and run only 1 hv line to the capacitor/gap).

Sounds like a fun project!
Take care,
Bart

Phil Tuck wrote:
> Hello Bart, everyone.
> Thanks for responding. Now I think about it aren't you meant to have just a
> single gap in the magnetic circuit ( i.e.: in just one leg) ?
> With my cores (Two pairs of UU's, one pair on top the other at the bottom) I
> would need to add 8 plastic shims to go between all the faces (2 x centre
> legs and 4 x outside legs). 
> I'm wondering if this is interrupting the magnetic path a bit *too much*
> -even using thin plastic. 
> Milling just two legs shorter on one side, and thereby leaving the magnetic
> path complete on the un-milled legs is not an option - I have the necessary
> gear but there's no way I am doing that!
>
> At present the secondary is wound over the primary on the centre leg,
> whereas I'll go for a secondary on each outside leg centre tapped. This
> means the gaps in all the legs will be inside a coil so that might help
> matters a bit.
>
> Regards
>
> Phil
> www.follytowers.co.uk/tesla
>
>      
>
>
>
> -----Original Message-----
> From: bartb [mailto:bartb at classictesla.com] 
> Sent: 26 March 2009 03:05
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Homebuilt Transformer - Can you add shunts?
>
> Richie used an air gap. This should be possible also with your core 
> type. This is probably easier than trying to insert shunts as a magnetic 
> leakage bypass with your particular core shown. Lot's of measurements 
> are needed until you find the amount of leakage current needed for 
> desired regulation. I think probably a simple air gap will be best with 
> this core of which you can do by inserting a thin sheet of poly (or 
> layers of) at the joining of the two halves.
>
> Take care,
> Bart
>
> Phil Tuck wrote:
>   
>> Hello.
>>
>> I am in the process of rewinding a transformer from a UK RADAR set. A
>> drawing of the core with sizes can be seen here 
>>
>>  
>>
>> http://homepage.ntlworld.com/follies/tesla/radartransformer.html
>>
>>  
>>
>> Eventually it will be a 2 to 3 Kva unit   ( originally it was 2Kva 8.25 kv
>>     
> @
>   
>> 250 m/a with  AWG 14 on the primary & AWG 24 on the secondary)
>>
>> Before I start finalizing turns etc, I wondered can I introduce a magnetic
>> shunt to limit the shorted current, like NST's use, and thus avoid having
>>     
> to
>   
>> use a Ballast?
>>
>> If so would I just need to introduce some packing between the jointing
>>     
> faces
>   
>> ?
>>
>>  
>>
>> Richie Burnett has done a similar thing with some inductors to stop
>> saturation at 
>>
>> http://www.richieburnett.co.uk/parts2.html#ballast
>>
>>  
>>
>> Looked at a few other webpages on homebuilt transformers but none seem to
>> use this method for a transformer though, but I thought this was the same
>> method employed by NST's
>>
>>  
>>
>> Thanks
>>
>> Phil
>>
>>  
>>
>>      
>>
>>  
>>
>>  
>>
>>  
>>
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>>
>>   
>>     
>
>
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