Since electric heating came into use long ago, it has been developed into products of various forms in many social places. In particular, recent remarkable progress in semiconductor switches toward large capacity and high speed has accelerated its technology improvement and application expansion. It can be much expected that the development of analysis technology and control technology using programmable controllers, will lead to a new electric heating process. This paper introduces our technology of industrial induction heating, arc heating, induction heating for the food industry, plasma heating and levitation melting, and surveys technical and demand trends of electric heating.

Technical progress in electric-arc furnaces has been remarkable in recent years, for example, high-voltage low-current operation in AC arc furnaces and higher efficiency attained by DC arc furnaces. On the other hand, measures against power supply system disturbance have steadily made progress such as self-commutating flicker compensators with greatly improved characteristics. This paper describes recent technical trends of arc furnaces for steel making and measures against power supply system disturbance.

Induction heating has rapidly spread because of its merits such as quick heating, clean heating, high efficiency and easy temperature control. This paper outlines the principle of heating with regard to a longitudinal flux method and transverse one and a survey of recent trends. Future induction heaters will be required to be high-quality and meet multikind small-quantity production as well as improved in effective use of energy and ease of operation, and also, to be pollution-free, gentle to the environment and low in price. The trends of typical induction heaters, inverters for power supply and process control are introduced.

A large-scale levitation melting furnace capable of melting metals up to about 2 ? has been developed. Its features are (1) an upper coil for melting, and a lower coil for levitating metals with low frequency, and two power supplies, (2) the cup-conical bottom of the cold crucible, (3) tapping from the bottom hole. This paper describes the principle, structure, metallurgical research, pouring simulation, distribution of eddy current, electromagnetic force, temperature and thermal stress, and cooling water flow analysis, citing the external view of the apparatus, and refers to the uses of CCLM and its application to larger capacity.

Plasma, a gathering of atoms and molecules from which ions and electrons separate, called the fourth state not belonging to any of solid, liquid and gas, is applied to various products in the electrical and the frontier industries. There are low-temperature plasma application such as CVD and thermal plasma application such as arc cutting and welding. From among the latter, this paper describes the principle and application of inductively coupled radio frequency plasma (ICP) and Fuji Electric's attitude to ICP equipment development.

The high-frequency (HF) inverter which is an important component of induction heating systems requires varied frequency and output according to heating conditions and heat capacity. Fuji Electric standardized HF inverters of 0.5 to 100 kHz and 20 to 4,000kW with thyristors, power transistors and power MOSFETs. Recently, it has developed a new series of higher frequency inverters of 500kHz and up to 1,000kW applying power MOSFETs. This paper introduces their standard specifications, features, circuitry configuration, including thyristor inverters and power transistor inverters.

Fuji Electric has completed a line of inverters using flat type MOSFETs, i. e. semiconductor switches for high frequency. This paper describes the features and applications of the MOSFET inverters. To apply these inverters to the domain where vacuum-tube power supply had been used so far, the main and control circuits were designed and high-speed stability and reliability were secured. Among the application examples, the power supply of 500kHz and 200kW for electric-resistance pipe welding is the first application of a semiconductor inverter in the world.

Fuji Electric developed a vortex electromagnetic stirrer for aluminum melting reverberatory furnaces in cooperation with Miyamotokogyosho Co., Ltd. Formerly, aluminum chips and UBC material that float on the melt and are not submerged in it are difficult to be melted in a reverberatory furnace. This vortex stirrer causes a vortex by giving the melt a shifting magnetic field as turning force; then aluminum chips and the like thrown into the furnace are drawn into the vortex and can be melted. The vortex stirrer is expected to be an indispensable equipment for reverberatory furnaces.

With conventional ladle smelters that were not equipped with a heater, countermeasures such as raising molten steel temperature and limiting molten steel treatment time have to be taken. Utilizing induction heating technology accumulated for many years, Fuji Electric has developed an induction heating ladle smelter which can efficiently heat molten steel in the ladle without overheating the ladle shell and improve the productivity and quality of multikind small-quantity products and trial pieces. This paper introduces its outline.

To meet recent growing trends towards protecting the environment and increasing the speed, Fuji Electric's induction heating inverters are widely used in the various fields of the food industry. This paper introduces their actual applications and advantages gained from introducing them. Main examples are food cooking apparatus such as electromagnetic cookers in hotel and restaurant kitchens, induction heating rice cookers and pancake cookers.