Factors affecting the current in the primary coil

[VNTC]

•L2C2 not in place
Primary current is proportional on DC supply voltage and the duration of the pulses applied on it
Example with C1=80nF, bus 340Vdc, haft bridge drive(full bridge drive equivalence Vbus*2)
*For the coil 5uH, primary current can reach 550A in after 60us.(image1)
*For the coil 10uH, primary current can reached 450A after 90us.
*For the coil 10uH, primary current can reached 390A after 110us.

•L2C2 in place, K=.16
Depend on the situation of the tuning the load resistor at secondary coil will reflect to primary coil to reduce or make grow the primary current. In good tuning it works something like a low frequency transformer (the primary current depend on the load on the secondary).

Image 2 schematic of a DRSSTC in 2 situation good and bad tuning
Image 3 Primary current grow gradually and maintain high level >350A, power out high>50kw
Image 4 Primary current maintain low level<150A, power out low<30Kw.

[Uspring]

The primary current rampup, disregarding secondary loading, can be calculated following chapter 3 here: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/mmc-tank-capacitor/ . It is based on the fact, that for every voltage switch of the bridge, the voltage change at the bridge is added to the primary cap voltage.

For a primary tank loaded by a secondary tank, the max primary current can be described by an effective Q of the primary tank, which is imposed on it by secondary loading. For a discussion of this look here: https://4hv.org/e107_plugins/forum/forum_viewtopic.php?163363

[Mads Barnkob]

VNTC, while I unfortunately does not have much to add, I just wanted to say I follow your discussions of theoretic operation with great interest. Uspring is sharp as usual