Coreless induction furnaces

The paper deals mainly with induction furnaces for steel melting, although some attention is given to other applications such as the case-hardening of steel. Construction of furnace bodies to avoid heating of the metal framework, and the fritting of refractory linings in situ, are discussed. Other apparatus in the furnace circuit is described, namely high-frequency generators, methods of switching condensers and the protection of the generator. The function of series condensers and the development of earth-leakage protection in furnace circuits are discussed. The changing characteristics of furnaces due to changes in the physical properties of the charge are described, as is the effect of lining erosion. The paper concludes with a short statement on valve-operated furnaces.