Frequency adjustment in induction heating systems

In induction surface hardening processes, the frequency has a decisive influence on the desired heating depth due to current displacement effects. Here, the demand for the AC voltage generated by the converter to be adjusted to the resonant frequency of the external oscillating circuit makes the exact adjustment more difficult. In order to achieve the desired heating depth and on the other hand to make the usage of different coil designs possible, many systems are equipped with options for frequency switching. Hereafter, various influences on the frequency by the components inside the external resonant circuit are presented as well as possibilities for adaptation.