Induction heating for industry

Electroheating by magnetically inducing high-power currents into metal has been an accepted industrial process for over half a century. During the last decade, rapid development in high-current solid-state devices has resulted in the gradual replacement of the motor generator by frequency converters for the generation of medium-frequency power (300 Hz to 10 kHz). Power at these frequencies is normally used for forging, forming and melting, and for deeper case hardening. Lower frequencies (50 to 200 Hz) are obtained straight from supply lines, or from magnetic multipliers; applications include forging and melting at high power levels. Higher frequencies between 100 kHz and 10 MHz are produced by radio-frequency systems, and processes include hardening and joining. This article summarises the main areas of induction heating and the systems used to generate and control these power sources, and includes extracts from a new book on induction heating by the authors, published this summer. Advantages of induction heating include fast and precise heating, clean and compact equipment and, in many instances, cost savings compared with traditional methods