Chang-Hung Hsu

Reducing audible noise for distribution transformer with HB1 amorphous core

In this paper, the way to reduce the audible noise of a distribution transformer is presented by incorporating a newly developed transformer core and a rigid-structure tank. The vibrations related tothe core structure and tank frame are considered, so that a distribution transformer with accelerometers mounted on the internal core and external tank, respectively, is addressed. In practice, the core with a new joint structure and the tank with a strong rigid-frame (H-type) are applied to a single-phase amorphous HB1-cored transformer with capacity 167 kVA for performance verification. Finally, a personal computer-based data acquisition platform is setup for signal measurement and processing. Experimental results demonstrate that the HB1 amorphous-cored transformer with the proposed core joint and rigid-structure tank can be performed well in the aspect of audible noise reduction.

Effects of magnetomechanical vibrations and bending stresses on three-phase three-leg transformers with amorphous cores

This paper explores the influence of bending stresses on the magnetic characteristics of three-phase transformers with amorphous cores. Different types of core structures, including C-cores and toroidal cores, and their magnetic properties are compared using VSM and XRD. The losses in the magnetic core of the three-phase transformer are analyzed using the finite element analysis for both design and measurement. In addition, experimental results indicated that amorphous-core transformers with rectangular corners had higher audible noise and vibration intensities. This is because the condensed distribution of magnetic flux lines in the corners of the core may create high magnetic inductions associated with high magnetostriction. Finally, experiments with three-phase amorphous-core transformers were performed to study the effects of magnetism and magnetostriction on their performance in terms of core loss, vibration, and audible noise.

Fe-based Composited Cores for Single-Phase Transformers Fabricated with High-Induction Amorphous Material

A composite-structured, high-induction, double-layered soft magnetic composite core (SMC) comprised of magnetic amorphous HB1-M, HB1, and SA1 materials was developed. A finite element analysis simulated results for the magnetic loss and magnetic flux density for three types of amorphous cores are quite different from findings for traditional magnetic core structures, such as laminated silicon steel, because the magnetostriction and permeability properties of composite-laminated no-cutting structures can be restrained. The SMC structure showed interesting results for magnetic loss, magnetic flux lines, core vibration, and sound level. The main advantage of transformers assembled with composited-cores of SA1 and HB1 over a higher-induction core single-phase transformer is the significant reduction of magnetic loss. However, the SA1 and HB1 composite core also showed worse results in terms of vibration and sound level because the magnetostriction and magnetic flux density in the core distribution are not qui...

Suppressing magneto-mechanical vibrations and noise in magnetostriction variation for three-phase power transformers

This study investigated the effect of magnetostriction-induced core magnetomechanical vibrations and noise on the magnetic properties of power transformers. The magnetostriction of grain-oriented Si steels was found to be extremely sensitive to compressive stress applied along the rolling direction and to tensile stress applied along the transverse direction. The compressive stress increased the variation in the magnitude of magnetostriction, which is correlated with core vibration and noise. A 2D model of the power transformer was used to simulate the noise and vibration variables through a finite element analysis.

Effects of magnetostriction and magnetic reluctances on magnetic properties of distribution transformers

This paper analyzes the causes of magnetic reluctance in silicon steel wound cores with multi step-lapped joint structures through the appropriate exploitation of simulated and experimental local flux distributions in an air-gapped core, to propose techniques that can enable the reduction of the resulting core loss and vibration. The magnetic magnetostriction forces in the lap-joint regions, constituting another significant source of permeability, can be controlled by rearranging the step-lapped joint structure. Then, the computed local flux distributions were compared with experimental data. Single-phase pad-mounted distribution transformers with a capacity of 167 kVA were used in this study. It is indicated that the multi-step lap joint can significantly reduce the core loss and exciting power by regulating the configuration of adjacent air-gapped distances. Finally, composite-core structures were also used to validate the reduction of magnetostriction, core loss, and vibrations, corresponding to single...

Correlation of magnetostriction variation on magnetic loss and noise for power transformer

Magnetostriction (MS)-caused strain in single-phase three-legged cores with different core cutting forms, which suffer from induced magnetic loss and noise, was studied. It is found that adopting each different core form types induces magnetostriction e variation in a transformer core operating with a high-frequency AC signal. The results are compared with finite element analysis simulations. It is also indicated that magnetostriction e variations are significant in the rolling direction and along limbs and yokes. In this paper, it is proposed that core corner sides and T-joint parts without cutting structure, the core exhibits lower core loss and lower heat dissipation due to the fact that the magnetic flux that passes through corner sides shows lower magnetostriction variation. The magnetic properties resulting from magnetostriction variation in core loss and heat dissipation phenomena are significantly different from other core forms because of stronger contributions from magnetostatic forces. The main contribution for reducing core loss and noise, making them much less in corner numbers and cutting-fabricated forms, can be expected to come from lower magnetic flux and magnetostriction variation.

Influence of Bending Stress on Magnetic Properties of 3-Phase 3-Leg Transformers With Amorphous Cores

This paper mainly explores the influence of bending stresses on the magnetic characteristics of three-phase amorphous transformers. Different types of core structures, including C-shaped and toroidal cores, are considered for a comparison of magnetic properties using VSM, XRD, and SEM. Among all specimens, those taken from the limb plane and the rectangular corner of a C-core have the lowest and highest coercivities, respectively. In addition, the crystalline property of Fe and α -Fe of rectangular cores is stronger than that of toroidal cores. Subsequently, the properties of magnetic loss and magnetic anisotropy are investigated. The experimental results of three-phase amorphous core transformers with a capacity of 100 kVA demonstrate that the toroidal core transformer has better magnetic characteristics in terms of lower core loss and exciting power than conventional C-core transformers.