A magnet’s magnetizing state largely affects the characteristics of a device that uses permanent magnets. A magnetization device performs magnetization by applying an extremely strong magnetic field to a magnet. The capacity of the magnetization power supply is also determined by multiplying the magnetization current by time. The production process requires that magnetization be performed by running a large current through a magnetization coil in an extremely short period of time. However, eddy currents are generated in the magnetic material to be magnetized when the currents time variations are too severe, opening the possibility that the intended magnetization distribution cannot be obtained. On the other hand, when the current changes too slowly the magnetizing device’s capacity needs to be expanded, leading to an increase in production cost. This is why the trade-off between production costs and whether sufficient magnetization can be carried out needs to be studied.
A magnetic field analysis using the finite element method (FEM) can handle the nonlinear magnetic properties of materials and eddy currents that are generated in the magnetic material to be magnetized when current flows through the coil. This makes it possible to discover how the magnetizing field will be generated and what effect it will have on the magnetization distribution.
This Application Note presents how to obtain the magnetization field distribution accounting for eddy currents in the magnetic material to be magnetized, the eddy current density distribution in the magnetic material to be magnetized, and the surface magnetic flux density of the magnet.
Magnetization Field / Eddy Current Density Distribution / Surface Magnetic Flux Density
This section shows the magnetization field in fig. 1, the eddy current density distribution in the magnetic material to be magnetized in fig. 2 and the magnet’s surface magnetic flux density in fig. 3.