In the computation of magnetic fields for rotating electric machines, transformers, and reactors, the hysteresis nonlinearity sometimes has to be taken into account. Nowadays, many scalar hysteresis models are known for one-directional fields. The main problem with using these models is that the models are complicated and they need much computation time. A new simple version of the scalar hysteresis model is presented for different computation tasks where the magnetic field is computed or where the magnetic state tracing of a core is needed. The major and minor hysteresis loops can be simulated. It is possible to make computations starting from the field strength as well as from the flux density. The model is based on the limiting hysteresis cycle and this measured cycle is used as the parametric data for the identification of ferromagnetic material.

Articles you may be interested inStress-and magnetic field-induced entropy changes in Fe-doped Ni-Mn-Ga shape-memory alloys Appl. Phys. Lett. 96, 071912 (2010); 10.1063/1.3309755 Shape memory and ferromagnetic shape memory effects in single-crystal Ni 2 MnGa thin films Large field induced strain in single crystalline Ni-Mn-Ga ferromagnetic shape memory alloy Magnetic shape memory ͑MSM͒ materials change their shape with the magnetic field. They can also be used in the reverse operation as sensors or voltage generators. The present paper demonstrates that large voltages are induced when the MSM material is mechanically compressed inside a MSM actuator. The experimental results reveal that voltages of close to 100 V were generated with a Ni-Mn-Ga MSM material subjected to short mechanical impulses, because of a change in its magnetization. The induced voltage depends on the geometrical and material parameters of the MSM actuator, as well as on the speed by which the MSM material changes its shape. A magnetic model for calculating the induced voltage is proposed and the measurement results from a MSM-type actuator are presented. The magnetic model demonstrates good accordance with the experimental results. The physical reason for the voltage signal is discussed and potential applications are proposed.

In this study, a vibration energy harvester is investigated which uses a Ni–Mn–Ga sample that is mechanically strained between 130 and 300 Hz while in a constant biasing magnetic field. The crystallographic reorientation of the sample during mechanical actuation changes its magnetic properties due to the magnetic shape memory (MSM) effect. This leads to an oscillation of the magnetic flux in the yoke which generates electrical energy by inducing an alternating current within the pick-up coils. A power of 69.5 mW (with a corresponding power density of 1.37 mW mm−3 compared to the active volume of the MSM element) at 195 Hz was obtained by optimizing the biasing magnetic field, electrical resistance and electrical resonance. The optimization of the electrical resonance increased the energy generated by nearly a factor of four when compared to a circuit with no resonance. These results are strongly supported by a theoretical model and simulation which gives corresponding values with an error of approximately 20% of the experimental data. This model will be used in the design of future MSM energy harvesters and their optimization for specific frequencies and power outputs.

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