Magnetostriction in nonoriented (NO) electrical steel is a possible source of vibration and acoustic noise in electrical machines. The anisotropy of the magnetostriction of NO steel can be far greater than that of its specific power loss which is often quoted. Also magnetostriction under rotational magnetization can be much higher than under alternating magnetization. This paper shows the relevance of magnetostrictive anisotropy to the rotational magnetostriction of a NO steel. An investigation of the effect of anisotropy in magnetostriction was carried out, followed by rotational magnetostriction measurements. A model based on an analogy of mechanical elasticity was used to describe the effect of magnetostrictive anisotropy on the rotational magnetostriction. Results show that a high value in rotational magnetostriction is mainly driven by its high magnetostriction in the transverse direction. The phenomenon is shown to be a source of asymmetrical deformation in the back iron of electrical machine cores where rotational flux predominates.

Magnetostriction in nonoriented (NO) electrical steels is a harmful source of vibration and acoustic noise in electrical machines. It is far more anisotropic than specific power loss, which results in more complexity in prediction of the vibration and acoustic noise. An investigation of the anisotropy in magnetostriction and mechanical elastic properties of a NO steel is presented in this paper. Measurements of deformation in the stator teeth of an induction motor model core were conducted in order to study the effect of the magnetostriction anisotropy. Strain due to Maxwell forces in the air gap was calculated and compared with the measured deformation. Measurement results indicate that anisotropic magnetostriction has a great impact on unsymmetrical deformation of the stator teeth of induction motor cores.

This paper presents a unified structure of the unbalanced synchronous reference current control strategies for single-phase grid-tied voltage-source converters to obtain a zero steady-state error in the line current. An arbitrary waveform is used as the orthogonal current for the stationary to rotating frame axis transformation of the reference and measured grid currents. Various choices of such orthogonal signals lead to different control structures with the same performance characteristics. This causes a temporary unbalanced system, in which double-line frequency components appear in the control loops during the transient state. The proposed method with cross-axis decoupling, tuned at the control loop bandwidth by greater than eight times the grid frequency, has better performance than the existing virtual balanced synchronous reference frame scheme. Absence of the orthogonal signal generation guarantees the stability criterion of the control scheme. A zero steady-state error is still achieved under conditions of uncertainty in the converter parameters. Simulation and experimental results of a 1.5-kVA pulse width modulation rectifier validate the proposed methodology.

Magnetostriction of nonoriented electrical steel was measured under rotating flux magnetization conditions which occur in AC electrical machine stator cores, and compared with the magnetostriction calculated from a model based on a mechanical elasticity analogy. Shear magnetostriction and magnetostriction perpendicular to the magnetization direction are accounted for in the model which leads to an accurate representation of magnetostriction throughout the electrical steel lamination plane. This has the potential for improving the accuracy of stator core deformation and vibration calculations.

This article reports an investigation into ferrite and nanocrystalline materials for the medium-frequency transformer of a dual active bridge DC-DC converter, which plays a key role in the converter’s efficiency and power density. E65 MnZn ferrite cores and toroidal and cut nanocrystalline cores are selected for the construction of 20-kHz transformers. Transformer performance is evaluated with a 1.1-kW (42–54 V)/400 V dual active bridge DC-DC converter with single-phase shift and extended phase shift modulations. The experimental results indicate that the toroidal nanocrystalline transformer had the best performance with an efficiency range of 98.5–99.2% and power density of 12 W/cm³, whereas the cut-core nanocrystalline transformer had an efficiency range of 98.4–99.1% with a power density of 9 W/cm³, and the ferrite transformer had an efficiency range of 97.6–98.8% with a power density of 6 W/cm³. A small mismatch in the circuit parameters is found to cause saturation in the nanocrystalline toroidal core, due to its high permeability. The analytical and experimental results suggest that cut nanocrystalline cores are suitable for the dual active bridge DC-DC converter transformers with switching frequencies up to 100 kHz.