Industrial Induction Heating - with a focus on multi coil solutions

Abstract

Most types of materials and components use heating during the manufacturing process, with a large potential for cost and energy savings. Induction heating is the most energy efficient industrial heating technology for many applications, but so far technical limitations has delayed large scale introduction. The difficulties relate to heating of large flat and curved surfaces, and, perhaps most important of all, the difficulties in achieving a uniform heat distribution. The efficiency of existing industrial induction heating systems on the market is often low, with clear demands for improvement. The first part of this work aims to improve the efficiency and manufacturability of induction heaters. By combining a newly developed core material, a silicon-iron powder composite, with litz wire for high frequency applications, very high efficiency heaters can be manufactured. The powder composite can be molded into any size and shape which allows building large, complex structures with integrated cooling. The results from this work have been commercialized and an increasing number of companies can benefit of substantial economical and energy savings in the production. The second part of the work concerns investigating a type of induction heating based on several coils, in order to achieve uniform heating. The method is called travelling wave and characterized by a fast propagating electromagnetic field that moves along the workpiece. The challenges related to multi-coil solutions are many, because of the interaction between the currents in the coils. The work contains results of the system behavior based on analytical models, simulation results of the heating pattern, and above all, experimental validation of the models. The general accuracy of the analysis of travelling wave systems has been greatly improved. Solutions to the challenges limiting the practical use of travelling wave systems are presented. Combining the new materials and production methods developed for induction heaters, with the technology of multi-coil heating has the potential to greatly improve the output from industrial processes in terms of cycle time, energy efficiency and product quality. For thermal cycling operations, the thermal mass is a huge problem. Given a method to supply uniform heating of thin workpieces provides entirely new conditions for many industrial processes; considerably reduced energy consumption, an increased production rate and products with new and improved properties