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Magnetic Flux Control in Induction Systems
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Teacher Hans De Keulenaer, Valentin Nemkov
Magnetic flux controllers are widely used in induction heating systems for concentration, shielding or redistribution of the magnetic field which generates power in the part to be heat-ed. Controllers help to obtain accurate heat pattern control, improve parameters of inductors and performance of the entire installation. In melting systems, especially in the case of vacu-um, cold crucible and other specialty furnaces, the magnetic control can provide large energy savings, magnetic field shielding, shorter melting cycles and optimized field distribution for enhancement of the metallurgical processes. Magnetic flux control, i.e. modification of the magnetic field distribution and intensity, may be accomplished by variation of shape and po-sitioning of the induction coil turns, by insertion of non-magnetic shields (Faraday rings) or the magnetic templates that may be called magnetic controllers.
Each method of magnetic control has its own advantages, drawbacks and limitations. Induc-tion coil designers pay main attention to optimization of active conductors (turns), their size, number and position. They try to avoid using additional components for the magnetic flux control in order to simplify design and reduce costs. This approach is understandable but it is correct only partially. Today’s competitive market with new materials and technologies, more strict demands to the product quality, safety and ergonomic requirements forces us to review the existing design guidelines and traditions. The main tool for that is computer simulation which can predict not only the process parameters but also life time of tooling (inductors) and service properties of the final products. In some cases it is difficult or even impossible to meet specifications of heating without application of magnetic controllers. Effects of using magnet-ic controllers, design guidelines and results prediction with the help of computer simulation are described in this presentation. Several case stories are based on more than 20 years of R&D and practical experience of sci-entists and practitioners at Fluxtrol, Inc. Presented material may be interesting not only for the induction heating community but also for all people using AC magnetic fields in techno-logical processes.