Kunihiro Senda

Influence of Various Non-Oriented Electrical Steels on Motor Efficiency and Iron Loss in Switched Reluctance Motor

The performance of a conventional 6/4 switched reluctance motor (SRM) has been studied using various non-oriented electrical steels for core material. The motor efficiency exhibited a strong correlation with the high-frequency material iron loss W10/400 (iron loss at 1.0 T, 400 Hz) through the influence on the motor iron loss although the fundamental frequency of the stator is about 100-200 Hz, while the material flux density B50 (magnetic flux density at 5000 A/m) had little influence on the motor efficiency. This paper also presents the calculation results of the motor iron loss based on FE analysis, which applies different equation forms to calculate the hysteresis loss according to typical flux density waveforms, and the computed iron losses agreed well with the measured losses. Then, it is shown that W10/400 is related well to the variation of hysteresis loss fraction in the motor iron loss for different materials and that the effect of core material on iron loss at higher frequency can be evaluated by their W10/400 values.

Effect of material properties on motor iron loss in PM brushless DC motor

The influence of material magnetic properties on the motor iron loss of a permanent magnet brushless dc motor has been studied using various non-oriented electrical steel sheets as stator lamination material. The motor iron loss has a strong correlation with the high-frequency material iron loss W/sub 10/400/ (iron loss at 1.0 T, 400 Hz), although the synchronous frequency is about 100 Hz. It is shown that the armature magnetomotive force causes strong pulses on the fundamental electromotive force waveform and that these pulses have a large effect on the motor iron loss.

Localized magnetic properties in grain‐oriented electrical steel measured by needle probe method

The accuracy of a needle probe method in measuring localized magnetic properties of grain-oriented electrical steel sheets was investigated and its application studied. The measuring error for the localized flux density was determined to be less than 1.7% for a load on the needle tip lighter than 300 g when the yoke structure was symmetrical with respect to the sheet plane. The average of localized iron losses measured with the combination of a needle probe and a Hall probe was in linear relation to the overall losses in the sheet. This method revealed that the localized magnetic properties vary markedly from location to location inside the sheet, and that localized iron loss depends on the localized flux density, domain wall spacing, and yaw angle of grain orientation.

Local magnetic properties in grain-oriented electrical steel measured by the modified needle probe method

Distribution of local magnetic properties in grain-oriented electrical steel was investigated using the needle probe method. The spatial nonuniformity of flux density was found to be affected by magentic poles on grain boundaries which mainly depend on the α angles between neighbouring grains and on the direction of grain boundaries.

Effect of hardness and thickness of non-oriented electrical steel sheets on iron loss deterioration by shearing process

Non-oriented electrical steels are widely used as the core material of motors. The magnetic properties of non-oriented electrical steel sheets have large influence on a motor efficiency. Punching is general manufacturing process in automatic fabrication of motor cores. This process is known to degrade the magnetic properties of non-oriented electrical steel sheets by plastic strain and elastic strain [1]. Therefore, the influence of the material characteristics such as grain size, hardness, and thickness on the deterioration of magnetic properties needs to be studied. In previous studies, the influence of grain size on the deterioration of magnetic properties was reported [2]. However, it is not clear about the influence of material characteristics except the grain size. The purpose of this study is to clarify the influence of thickness and hardness of non-oriented electrical steel sheets on the deterioration of iron loss by shearing process.

Investigation of the magnetic properties of Si-gradient steel sheet by comparison with 6.5%Si steel sheet

In this study, we investigated the magnetic properties of Si-gradient steel sheet produced by CVD (chemical vapor deposition) siliconizing process, comparing with 6.5% Si steel sheet. The Si-gradient steel sheet having silicon concentration gradient in the thickness direction, has larger hysteresis loss and smaller eddy current loss than the 6.5% Si steel sheet. In such a loss configuration, the iron loss of the Si-gradient steel sheet becomes lower than that of the 6.5% Si steel sheet at high frequencies. The experiment suggests that tensile stress is formed at the surface layer and compressive stress is formed at the inner layer in the Si gradient steel sheet. The magnetic anisotropy is induced by the internal stress and it is considered to affect the magnetization behavior of the Si-gradient steel sheet. The small eddy current loss of Si-gradient steel sheet can be explained as an effect of magnetic flux concentration on the surface layer.

Evaluation of stress distribution due to shearing in non-oriented electrical steel by using synchrotron radiation

The influence of the shearing process on the iron loss of non-oriented electrical steels with grain sizes of 10 μm-150 μm was investigated. The deterioration ratio of iron loss was clearly smaller in sample with small grain sizes. The droop height, reflecting the amount of plastic deformation, displayed a good relationship with the deterioration of iron loss under the effect of the material grain size. To clarify the strain distribution around the sheared edge, the elastic strain in a sheet sample with the thickness of 0.30 mm and grain size of 10 μm was evaluated by using synchrotron radiation. The width of the region of elastic strain due to shearing was two or three times of the material thickness. The results of the plastic strain distribution obtained by the measurements were then used to estimate the iron loss deterioration rate in 5 mm width sheared samples. The estimated loss deteriotation coincided with the actual measured iron loss.

Effect of material properties on motor iron loss

In the present work, a commercial PM brushless DC motor has been investigated using various non-oriented electrical steel sheets for the stator lamination. Measured data and calculated values by time-stepped finite element analysis are compared to evaluate the effect of material properties on the motor iron loss.