Opera-3d Magnetization and Hysteresis Module
Alongside industrial partners, Opera has developed a semi-empirical method for modelling hysteresis. When users input a measured major symmetric loop, easily obtained from measurements or published data-sheets, and imported into Opera as a magnetic characteristic table, Opera can supply a trajectory from the magnetic behaviour.
The Opera hysteresis model includes the issues of nested minor loops and ‘wiping out’ of minor loops, which occurs when the trajectory goes through an earlier turning point. Usefully, Opera recognises oscillating fields and minimises the storage of turning points.
Treating transition to saturation automatically, the simulation overcomes any limitations in the user’s data. All of Opera’s transient electromagnetic simulations offer hysteretic material models, including dynamics, rotating and linear motion and demagnetisation.
Opera-3d offers users the ability to model hysteretic materials under transient conditions using a B(H) trajectory-following algorithm. Users can simulate hysteretic materials in conjunction with the transient and motion electromagnetic solvers.
With this module users only need to supply data for the major hysteresis loop. Opera’s sophisticated algorithm uses a reconstruction technique to determine minor loops and turning points of the trajectory. It also erases turning points when the magnetization of a material exceeds the previous excursion. The algorithm correctly transfers to the saturated material curve beyond the end of the user data, in the same way as for anhysteretic materials in Opera-3d.
Magnetization and Demagnetization of Permanent Magnets
The result is a magnetized sample, where the magnetization distribution is correctly defined. This can then be used in other simulations to model the performance of the magnetized sample in its designated application (eg. an electrical machine).
During the simulation of the application further demagnetization and remagnetization of the sample in the application device due to the presence of current sources can also be modelled.
The Opera-3d (de-)magnetization analysis module (DEMAG) can be used to compute the magnetization of permanent magnet materials by time varying electromagnetic fields in three dimensions including the effects of eddy currents.
The values can then be transferred to the standard Opera transient solvers. In such a simulation where the applied field from current sources etc are opposing the magnet’s field, the variables will show the operating point of the magnet. In a transient simulation, they will show the lowest operating point that was reached during the transient event.
Demagnetization in service can be modelled. The minimum field will be tracked and updated during subsequent simulations, and the appropriate demagnetization curve or recoil permeability will be used.