Induction converter circuits consist of two main
topologies. The resonant half−bridge uses 600 or 650 V
IGBTs and operates over a range of 20 – 70 kHz, while the
quasi−resonant topology uses 1200 V or 1350 V IGBTs and
typically operates at 25 – 30 kHz. At 30 kHz, the resistance
is 3.2 for the cast iron pan to 0.3 for the aluminum pan.
It can be seen that due to the higher resistance of the cast iron
pan, the losses will be considerably greater and therefore, the
pan will be more effective at heating.
It should also be apparent, that to reach a similar resistance
for the aluminum pan, the operating frequency needs to be
close to 1 MHz. This is not a practical operating frequency
for today’s IGBTs.