An induction furnace is an apparatus that uses high-frequency induction heating to melt metal. Running current through the coil surrounding the crucible starts electromagnetic induction phenomena, which generate current in the metal in the crucible. This current produces joule losses in the metal, which are used to heat and melt it. Magnetic yokes are arranged around the coil. The yokes are used as strong components that prevent the Lorentz force generated by the coil from damaging and deforming it. The magnetic yokes also reduce the leakage flux that flows out of the appliance, preventing unintended heating in surrounding structures. Keeping the amount of material used in the magnetic yokes to a minimum makes it possible to reduce the cost of the apparatus.
To understand the magnetic flux that spreads from the induction furnace, it is necessary to use the eddy current distribution and magnetic flux flow in the metal in the crucible, as well as the concentrations in magnetic flux caused by the positions of the yokes.
This Application Note displays magnetic flux density distribution to evaluate the differences in magnetic flux with and without yokes.

The magnetic flux density distribution generated in the yokes and the air region is shown in fig. 1. When the yokes are present, there is less leakage flux than when they are not present. This means that it is possible to prevent a steel plate outside of the yokes from being heated.

The joule loss values of the molten metal are shown in fig. 2. There is 5% more joule loss in the furnace with the yokes than without them, so it is applying energy to the molten metal efficiently.