[ §5 · calculators · soft switching ]

Soft switching (k²Q)

Answers “does my SSTC switch softly or hard”. The condition is Uspring’s; getting to it from Burnett’s reflected model was done here.

coupling ksecondary Q

k²·Q 25.00current lags voltage by 2.3°minimum Q for k=0.5 4 Essentially clean ZCS.Resonant current far outweighs the magnetising current,so the losses are mostly conduction.

formula

I_res / I_mag = k²·Q          φ_lag = arctan( 1 / (k²·Q) )

limits

SSTC only: a primary with no capacitor. With a tuned primary the model does not hold; there it is the two-pole picture.

First-harmonic estimate. The magnetising current is actually triangular, not sinusoidal.

Q is the loaded Q at that instant. Without an arc it is several times higher than with one, so a coil travels rightwards along this scale during the burst.