Three-phase induction heating coils

Abstract

IN THE 60-cycle field of induction heating a 3-phase system is desirable. The advantages of 3-phase power is fairly obvious. In most cases a large amount of power is required and a balanced 3-phase load is very practical. Hence, 3-phase induction heating coils have been used to a large extent in 60-cycle heating of aluminum and brass. Since the size of stock to be heated is large in cross section, which is the primary reason for 60 cycle, the amount of energy required to heat the material because of its large mass is, in many cases, quite high. In the past, large billets, 4 inches to 30 inches diameter of aluminum, as well as brass, 4 inches to 10 inches in diameter, have been heated primarily for extrusion. Temperature uniformity is mandatory for high-quality results. In the case of special brass alloys, the temperature must be maintained at ±10 F (degrees Fahrenheit) throughout the billet. Induction heating is primarily a very rapid heating process taking seconds or minutes to heat, while other methods of heating require hours. Because of this rapid heating, temperature patterns follow closely magnetic flux patterns; also due to the rapid heating, sufficient time is often lacking for equalizing.