I slotted my 1256B variac core, test results

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Oxandale" <toxandale-at-cei-dot-net> 

Thanks again for comments in regards to the original posting. Here are some
numbers I recorded comparing two 1256D variacs (one with a slotted core and
the other unmolested). Before my Sencore LC meter bit the dust, these two
were within a couple of mH of each other at full winding (terminals 1 and 4)
prior to any slotting of the core on one of them. I am not at the current
time using the variac as a sole means of ballast, but instead have placed it
in series with a fixed winding ballast, as my goal is to achieve a 0-30amp
output using as close to a full sweep (full winding usage) of the variac as
is possible.

The un-modified variac (at a 150 vac output (to the coil) test voltage)
achieved a 5-25amp variance within a ~70º sweep of the winding.

The modified variac achieved this same 5-25amp variance in a broader ~160º
sweep of the winding. Moderation of the power increase was much easier with
the slotted core. Also, the exponential increase in current as the windings
were reduced (toward the last 25% of the travel) was not nearly as abrupt as
with the un-modified variac.

The results now bring up a question I'd like to throw out to you guys. I
would like to place two modified variacs in parallel so that I could
increase my current flow without damaging my variacs (for larger future
projects). With a paralleled ballast (using 2 variacs) effectively reduced
to 1/2 the amount of the inductance provided from one variac, can I assume
then that I may be able to achieve a full scale sweep of the ganged parallel
wired variacs for even more moderation of current control?

(un)Terry