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Re: Variacs in parallel ?
Hi Bert,
Bert Hickman wrote:
>
> Commercial paralleling chokes are actually small, high current, 1:1
> transformers. They are simply a single center-tapped high-current
> winding wound on a silicon-steel core.
>
> <snip>
> Vout = [V1-(V1-V2)/2]
> |
> |
> To Wiper of + Vx/2 - | + Vx/2 - To Wiper of
> Variac 1 <---------OOOOOOO----o----0000000---------> Variac 2
> V1 ----------------------- V2
> -----------------------
> -----------------------
> Common Core
>
After a lot of thinking, I finally figured out how this would work:
If the input voltages on both ends are equal, the magnetic field
in the core would be nil because the two halves of the coil are
effectively opposite phases and would induce opposite fields that
would cancel each other. If one side were greater than the other,
it's field would overpower the field from the other side. Thereby
reducing the voltage on the greater side, and increasing the voltage
on the lower side.
Neat trick :)
Question 1, how many turns on what size core for a 30 amp system???
Question 2, How do you tell if it's working??? (I have all the
stuff I need to start experimenting on this, I just have no clue
as to how to tell if what I've made is doing it's job)
Question3, you mentioned silicon steel cores, I take it you don't
mean a standard "E I" type laminated cores??? (If "that's" the
case, I have something that will fit the bill *perfectly* :)
>
> For a 3-phase variac you'd need chokes between pairs in a tree
> configuration:
>
>
> W1 ------------
> O
> o-----------
> 0 |
> W2 -------o---- |
> | |
> | o----------- Vout
> | |
> | |
> ----- |
> O |
> o-----------
> 0
> W3 ------------
>
> A bit of heavy gauge wire or strapping and some transformer
> laminations should be sufficient to do the job, and one heck
> of a lot less expensive new paralleling chokes.
Someone suggested another solution where you wind 3 coils on a single
core, but there was no further information. Given the choice, I'd
rather wind a single core, rather than 3, separate ones. Does anybody
think this would work or have any idea of how many turns on what size
core???
I have cleaned off a bunch of cores and have a matched set of 3
that I could use to do the 3 center tapped method if I have to.
It's just that I had planned to use these for current limiting
reactors.
Any help or clarification would be greatly appreciated.
Paul