Daichi Azuma

Audible Noise From Amorphous Metal and Silicon Steel-Based Transformer Core

Model cores based on amorphous SA1 and HB1 alloys for pole transformers were prepared and their audible noise was measured in terms of A-weighted sound power level in a hemi-anechoic chamber in accordance with ISO 3744 standard. The two amorphous cores annealed under optimum conditions to minimize the audible noise showed the same sound power level of 56 dB as M3 core at their typical operating flux densities. It was found that A-weighted sound power levels increased above 1.4 T for SA1 core and above 1.5 T for HB1 core. This provides design limitations for transformer cores based on amorphous alloys.

Core Loss in Toroidal Cores Based on Fe-Based Amorphous Metglas 2605HB1 Alloy

Amorphous ribbon exhibits low power loss. However, core loss of amorphous ribbon based toroidal cores is about twice as large as that of the ribbon even after field annealing under an optimum condition. In the present work, effects of residual strain and inter-laminar eddy-current loss on loss increase were examined for toroidal cores based on recently developed Metglas 2605 HB1 alloy which has a high saturation induction Bs of 1.64 T. The results show that: 1) with increase in residual strain, core loss and hysteresis loss are increased and no significant change in excess eddy-current loss was observed, and 2) there is no significant difference for frequency dependence of eddy-current loss by varying packing factor from 83% to 87%. This implies that there is no loss increase due to inter-laminar eddy current.

Acoustic and Soft Magnetic Properties in Amorphous Alloy-Based Distribution Transformer Cores

A new amorphous Fe-based alloy, Metglas® 2605 HB1M, has been developed for distribution transformer cores, modifying the chemical compositions of a conventional alloy. The distribution transformer model cores based on HB1M and conventional Metglas® 2605 HB1 alloy were annealed with magnetic field and then evaluated on their acoustic and soft magnetic properties. It has been found that A-weighted sound power levels and exciting power of HB1M-based cores are lower than those of HB1-based cores. These transformer performance improvements result from the magnetic anisotropy being induced more easily in HB1M than in HB1 alloy.

Domain structure and magnetization loss in a toroidal core based on an Fe-based amorphous alloy

By utilizing a wide-view Kerr-effect magnetic domain observation system designed for domain observation on curved surfaces, domain images were taken on the surface of a toroidal core based on an Fe-based amorphous alloy. The results of the observation are discussed in terms of Bertotti’s eddy-current loss model, helping to clarify the concept of magnetic objects proposed by the model.

Effect of residual strain in Fe-based amorphous alloys on field induced magnetic anisotropy and domain structure

Field induced magnetic anisotropy in two Fe-based amorphous alloys with different saturation induction levels (1.56 T and 1.64 T) was investigated by varying magnetic field strength and annealing temperature and domain images were taken on these samples. Residual strain was evaluated by measuring coercivities of the materials after stress-relief annealing. These results are discussed, clarifying the difference between the two Fe-based amorphous alloys.

Remote Temperature Sensor Based on Amorphous Metal Strips

A new remote temperature-sensor configuration based on amorphous metal strips utilizing magnetic harmonics is evaluated. The basic principle of operation is to utilize shape anisotropy effects, high magnetic permeabilities, and Curie transitions of amorphous metal-based ribbon. Because of the ease of controlling Curie temperatures of amorphous alloys, temperature-specific sensors can be designed. An example is shown for a temperature sensor in a rotating machine.

Study on Standard Measurement Method of Magnetic Property of Fe-Based Amorphous Strip—Round Robin Test Results

In order to establish a standard measurement method for Fe-based amorphous strip, an amorphous single-sheet tester (AM-SST) has been investigated. An international round robin test (RRT) was carried out among International Electrotechnical Commission (IEC)/ TC68 experts in 2014. The AM-SST based on the proposed standard measurement method was built and investigated for its adoption by IEC. In this paper, the outline and the results of the RRT are reported. The repeatability of specific total loss with H coil and magnetizing current methods by using the AM-SST proposed is shown.

Distribution of magnetic field strength inside exciting coil of single sheet tester

The double H-coil method was proposed to detect magnetic field strength on the surface of a specimen more accurately than the single H-coil method. In this paper, the distribution of magnetic field strength inside exciting coil of a single sheet tester (SST) is measured simultaneously by the single H-coil method using four separated H-coils. They are placed at different distances from the surface of the specimen and thereby enable us to evaluate the influence of the position of the H-coil on the measurement accuracy of magnetic properties. As a result, it was revealed that the magnetic field strength and specific total loss increase linearly as the distance of the H-coil from the surface of the specimen increases. However the increasing rate of the specific total loss is smaller than that of the magnetic field strength and within the range of required measurement reproducibility.