Masayoshi Ishida

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.

A New High Flux Density Non-Oriented Electrical Steel Sheet and its Motor Performance

A new high flux density non-oriented electrical steel sheet (JNP Core) has been developed. The magnetic flux density of JNP Core is enhanced more than 0.02T compared to an existing high flux density material (JNE Core) with nearly identical iron losses. There are two kinds of Si amount materials (JNP5 and JNP7) with thicknesses of 0.35 and 0.50 mm as in conventional non-oriented electrical steel sheet. The new steel is characterized by an improvement in its recrystallization texture. JNP Core is thought to be suitable for lamination material of PM motors or induction motors due to its high flux density and low iron loss. An in-wheel IPM motor for EV was made and the motor performance was tested. The motor efficiency and torque was improved by applying JNP5 material instead of conventional electrical steel sheet. Furthermore, the efficiency of induction motors using JNP Core as stator lamination material improved by more than 1% in the case that the operating flux density is over 1.6T.

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.

Intergranular Flux Creep in Ceramic YBa2Cu3Ox

Magnetic relaxation in crystallographically aligned superconducting ceramics YBa2Cu3O was measured to study the kinetics and anisotropy of flux penetration into intergranular region. With use of a thermally activated flux motion model, the activation energy of the intergranular flux creep was evaluated as 4.0±1.0 meV and 3.7±1.1 meV for external magnetic fields perpendicular and parallel to the ab-plane, respectively. Implications of the apparent isotropy are discussed.

Processing of Dense, Fine Grained YBa2Cu3Ox Ceramics Using a Spray-Drying Technique

High-Tc superconductor YBa2 Cu3 Ox has been synthesized using a spray-drying technique with special reference to the influence or the purity of the starting reagents on microstructures and superconducting properties. Sintering is enhanced and high density is easily obtained with ultrapure reagents of acetic salts. Doping with Sr to examine the impurity effects of reagents of conventional grade has resulted in porous microstructures. Magnetic field dependences of magnetization and critical current density of the ceramics are significantly dependent on the grade of the starting reagents.