Soft magnetic composites (SMCs) based magnetic cores are attractive in high frequency inductor design. The desired overall core permeability of SMC core can be achieved by adjusting the powder size, addition of insulation material and phosphoric acid, and pressure during the preparation process to reduce the air gap loss and ease the inductor design. The nanocrystalline alloy (Fe-Cu-Nb-Si-B) is an emerging SMC with high saturation flux density and low hysteresis loss, showing potential suitability for SMC based magnetic cores. To date, nanocrystalline alloys are mostly used in form of laminated ribbon for magnetic cores and nanocrystalline powder SMCs have been seldom used in practice. Also, neither experimental validation nor comparison with other commercialized and commonly used SMC cores has been reported. In this paper, the structure and manufacturing process of nanocrystalline powder cores are introduced. The calculation of core loss is defined for the nanocrystalline powder core. The characteristics and performance of the nanocrystalline powder toroidal core are compared with those of existing commercial SMC cores such as Fe-Si powder (X flux), Fe-Ni powder (High flux), Fe-Si-Al powder (Kool Mµ), Fe-Ni-Mo powder (MPP). Experimental results are conducted at frequencies from 100 kHz to 600 kHz to verify the loss calculation and feasibility of this new nanocrystalline powder core.

This letter reports characterization of the novel nanocrystalline flake ribbon (NFR) soft magnetic material. The comparative analysis among the ferrite N87, N27, and the NFR is presented at different temperature, frequency, and peak magnetic flux density, respectively. Experimental results prove that the NFR has lower loss density, higher magnetic flux density saturation, and better temperature stability from 85 to 300 kHz. A LCL resonant tank based circuit is employed for large signal characterization. The mass-based stacking factor of the NFR core is adopted to describe the core structure. This letter suggests that the NFR is a good alternative to the ferrite for high power magnetic cores due to its superior performance and flexibility structures.

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This paper analyzed and compared the complex permeance model (CPM) and nonlinear analytical model (NAM) for surface-mounted permanent magnet (SPM) motor using voltage source inverter (VSI). For linear CPM, the slotting effect is represented using the improved complex permeance function that describes the real slot shape rather than infinitely deep slot. NAM is extended from CPM and it replaces the magnetic potential drop of stator iron by the equivalent virtual current in the slotopening and tooth-tip to account for nonlinearity effect. The nonlinear inductance of SPM motor including the main phase inductance, slot leakage inductance, tooth-tip leakage inductance, and end winding leakage inductance is calculated using the frozen permeability method, which is the key to solve the electric circuit with VSI. The instantaneous back-EMF is calculated from the nonlinear back-EMF coefficient and the back-EMF neglecting iron nonlinearity. The electromagnetic torque obtained from motor model is used in the mechanical model and then the rotational speed and rotor position are obtained for the electric circuit model. Hence, the iterative solving process for the motor system is established to calculate the transient performance of SPM motor using VSI. Compared with CPM, NAM can greatly improve the calculation accuracy, which is also validated by both FEM and experiment. Besides, the proposed NAM is computationally efficient, which is useful for both motor design and motor control.

This article introduces a toroidal nanocrystalline powder core with a trapezoidal cross section. The nonuniform magnetic flux distribution of toroidal cores with different cross-sectional geometries is discussed, the inductance equations are derived, and the geometrical optimization factor is given in order to retain the highest possible inductance value while minimizing material usage. A ten-turn coil is wound on the core, with the measured inductance values showing a good match with both finite element method (FEM) and mathematical calculation. The near-field electromagnetic interference (EMI) radiation in close proximity to the inductor is investigated by both FEM and experimental validation, and the toroidal core with a trapezoidal cross section has shown reduced EMI. By adopting a trapezoidal cross section for the toroidal core, a 30% reduction in material usage and lower EMI are achieved, albeit with a compromise of 14% in inductance.