Re: Help with a one shot device

From: mike (spamme0_at_netscape.net)
Date: 03/05/05 

Date: Sat, 05 Mar 2005 14:07:58 -0800

Rich Grise wrote:
> On Fri, 04 Mar 2005 21:34:39 -0800, mike wrote:
>
>>Jeff wrote:
>>
>>>Mike,
>>>
>>>Thanks, I am making mine from a MOT also. Had not really considered
>>>the larger fast amp draw. Great info on the whole process.
>>>
>>>Did you find a 220V transformer (I have had no luck finding anything
>>>other than 110V units from the scrap piles) from a microwave or was it
>>>110V originally and you rewound the primary too?
>>>
>>
>>I'm in the US. They're all 120V. The SS Relay is 240V simply 'cause I
>>had it in the junk box. A microwave transformer is a lousy choice for a
>>spot welder. Designed to be low coupling for the microwave application.
>
>
> In the spot welder designs I've seen on the web that use MOTs, they take
> out the shunts. In this picture,
> http://www.neodruid.com/images/dscf0145.jpg
> you can see the shunts in the window between the windings. Toss them. (or
> put them in your "there must be a use for this crap somewhere" box) Those
> things protect the transformer and maggie by bypassing some of the flux.
> Lose them, and you have a regular transformer. Of course, you already
> know to toss the secondary and wind 3-4 turns of #2 weld cable. :-)
>
> Good Luck!
> Rich
>

I agree, toss the shunts, but I'm not sure that's the whole story.
Is the core made of the same stuff as a real transformer?
YOu also lose some coupling with the side-by-side windings.
I expect there are some rules of thumb about this??
mike 

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