In-Line 3-Phase Variac
Help needed from the engineers/professionals (Bert, Malcolm etc.)......
You may recall I found a nice 3-phase variac, complete with control motor
etc and posted a picture of this to the list several weeks back. See:
Now I have since been thinking about this and I have some concern. Most
3-phase variacs are simply 3 ganged single phase units on a common shaft
.... easy !
This unit is 3 linear windings, one on each leg of a double-E core. I had
originally planned to use the three windings (15A each) in parallel for a
45A variac - very conservatively looking at the size of the cores and wire
gauge. However ....
1. Trying to visualize the core magnetic fluxes, if I simply parallel the
3 windings there will be no continuous path for the flux to follow.
Am I thinking correctly here ??
Or has my lack of knowledge brought me unstuck again !
(alternatively would this simply act as a form of current limiting)
2. Thinking further, if I used just the 2 outside legs in parallel, then
the flux could take the center leg - providing the core area is sufficient
(which I suspect it would be). Is this an adequate solution, assuming my
concerns are correct in point 1 ?
3. Taking the mental process another step. Could I construct a current
limited variac by running the outside 2 legs in parallel, then short the
center-leg to the wiper ? (which could then be independently variable)
Only problem with the idea in (3) is the wipers are mounted on a common bar
which is motor controlled. Separating the center wiper would be messy, but
All help and ideas appreciated.