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In this paper, the transient thermal response of a conventional double layer switched flux permanent magnet machine is studied for both healthy and fault conditions such as inter-turn short-circuit. A highly optimized and accurate co-simulation model for different operating conditions is developed requiring low computation and time resources. The electro-mechanical models for both healthy and faulty operation are implemented in Matlab/Simulink while the thermal model is implemented using 3D FEM software. Both models are dynamically coupled to enable the influence of temperature rise on the electromagnetic performance and vice versa to be predicted. Operation under various conditions are investigated and it is found that the temperature rise under fault conditions and high speed can lead to irreversible demagnetization of the permanent magnets. The superposition principle is used to accurately estimate the impact of short-circuit currents on the temperature rise. A series of dynamic tests are carried out to validate the transient thermal response prediction when operating during both the healthy and fault conditions.

Abstract:The irreversible magnet demagnetization phenomena are investigated in this paper, under both healthy and short-circuit conditions for a switched flux permanent magnet (SFPM) machine. The temperature effects on permanent magnet material are taken into account and the influence of short-circuit current over demagnetization is evaluated. In order to calculate the short-circuit current (mainly inter-turn short-circuit), the MATLAB/Simulink model has been employed. The aforementioned short-circuit current is then fed to the finite element model, so the demagnetization analysis can be carried out. Various fault scenarios are investigated, including high speeds and high fault severity. It is found that the short-circuit current has limited effect on the magnet demagnetization due to particular features of the SFPM machines. The mechanism of demagnetization has been revealed and found out to be mainly due to temperature rise and poor PM materials utilization. Experiments have been carried out to validate the MATLAB/Simulink model for short-circuit current predictions.

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The large signal operation of the bulk acoustic wave (BAW) resonators is characterized by the amplitude-frequency effect and the intermodulation effect. The measurement of these effects, together with that of the small signal frequency characteristic, are used in this paper for the parameter identification of the nonlinear circuit models developed previously by authors. As the resonator has been connected to the measurement bench by wire bonding, the parasitic elements of this connection have been taken into account, being estimated solving some electrical and magnetic field problems