Induction Heating and Flux Field Intensifiers

Induction heating is the process of heating a conductive material by generating a circulating flow of electrons or eddy currents in the material. This effect can be intensified or in some cases shielded by using materials that control the magnetic flux field generated by the induction coil. These materials are called magnetic flux concentrators or flux intensifiers.

Flux concentrators are made from high permeability, low power loss materials. The most common examples are a molded material consisting of iron powders in a compacted non-conductive binder, or lamination style concentrators. Both will have similar results but specific applications or geometries may dictate the use of one or the other style.

Most applications calling for flux intensifiers require the field to be compressed or intensified in certain area. Under normal conditions the field of the coil is drawn to the load side closest to the work piece. Some of the field naturally flows around the other sides of the coil. This is where flux intensifiers can be used to help focus more the energy towards the work piece. By wrapping the sides of the coil and creating an opening towards the work pieces, the additional flux field is focused into a smaller area and results in improved coil to work piece coupling.

The same materials that are used to focus the flux fields towards a work piece can also be used to protect certain areas from undesired hardening. If for example, a coil is wrapped around a shaft with a flange, the natural tendency will be for most of the field to be attracted towards the shaft area. As the coil gets closer the flange, a certain amount of the energy is drawn towards the mass area next to the coil, by the proximity effect. If that area is required to remain soft, flux intensifiers can be used on the face of the coil in between the coil and the flange to prevent heating in that area. Conversely if the area is required to be heated, the effect can be intensified by placing the intensifier material on the side opposite the flange so that the coil is between the flange and the concentrator.

The use of flux concentrators can make difficult applications easier. But the application and development of a coil with flux concentrators can involve additional time and costs to properly develop the coil to the application. We at Zion industries use flux intensifiers as dictated by the application and have the ability to design, manufacture and develop the tooling with flux concentrator materials in house. If you have a challenging induction application, we would be glad to review it with you.

Lou Ghinga
Zion Industries, Inc.

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