Re: In-Line 3-Phase Variac
At 16:07 20/08/99 -0600, you wrote:
>Original Poster: "Choad" <choad69-at-geocities-dot-com>
> What happens if you parallel the two outer windings and connect the
>middle winding in parallel also but reversing the leads. As H1-H2-H1 and
>H2-H1-H2. Seems to me that the flux lines should ge the oppisite directon
>for that winding which would be the same direction as the other two legs. If
>you just put voltage on the two outer windings in parallel won't you get the
>same voltage in an opposite phase on the middle winding? This idea is
>working in my head. So will someone please tell my why I'm wrong and this
>won't work. :)
I'm no engineer, which is why I asked the question in the first place, but ....
1. Like most variacs there are a number of windings beyond the 'primary',
so the output goes to about 110%. Reversing the primary to the middle leg
this would fail.
2. If you imagined the case of just 2 legs on a rectangular core, this
would effectively double the flux through the core and risk saturation.
3. As I think Bert pointed-out, if we connect the 2 outer legs, then
double the flux will be returning through the centre leg, so the dV across
the windings will be *double* the supply dV at 180degree phase
shift. Connecting the supply to this would be like connecting the output
of a 1:2 transformer back to the primary....... where there is smoke ......
The great advantage of this unit is its size (and cost!!) and heavy
construction. Two of the 3 windings will be ample for my task.
I'm going to do some test measurements under load today. I'll post them to
the list for those interested.