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Continuing on this SSSR scheme of mine, I've now mounted two primary
modules, each consisting essentially of 3T on 12"-diameter driven by a
p-p pair of MOSFETs, with power source capable of up to ~330 VDC to the
MOSFETs and operating at ~125 KHz. There has been discussion here as to
whether to connect those two primary drivers effectively in series,
using a bifilar choke or chokes to deliver the DC power to them, or
whether it will produce just as many ampere-turns merely to connect the
two driversto the same DC power source, directly in parallel. In both
cases, the gate drives are transformer-coupled. The primaries are
coaxial, co-planar, wound with turns close together, and are located
directly against the bottom of the secondary.
Fortunately I've made provision for the bifilar chokes because
initially, following the simpler connection, I find that a) each primary
+ driver produces the expected primary currentwhen operated by itself
(measured by a current transformer through which 1 turn of each primary
passes). However, b) when I connect both of them similarly I get a
total primary current increase of only around 10%. This seems to tell
me what I had rather suspected, namely that the primaries must be
connected effectively in series by means of "floating" at least 3 of the
final 4 primary drivers as I describe while galvanically connecting the
primaries themselves in series. That's the scheme I'd used years back
when I actually got nice spark breakout from the 6x24 toroid, with no
breakout point, which I am aiming for again.
I'm guessing that the ~10% increase in current is due to the decrease
ineffective dc resistance of the resultant primary, nothing more. So...a
little re-wiring will be in order.