This article presents the up-to-date conclusions concerning the design of t
he three element L-LC resonant inverters for induction heating applications
. The main properties of the L-LC resonant tank are presented. The advantag
es of the L-LC circuit over the series resonant inverter (SRI) are explaine
d: namely, its current gain and short-circuit robustness. Finally, a transf
ormation algorithm is proposed which allows substitution of the SRI by an e
quivalent L-LC circuit, that is to say, an L-LC which achieves the same out
put power at the same resonant frequency with the same heating coil and pie
ce.