Fuminori Ishibashi

Cooling airflow in unidirectional ventilated open-type motor for electric vehicles

In this paper, the cooling airflow in a unidirectional ventilated open-type motor for electric vehicles (EV) was studied. Numerical fluid analysis was performed on the airflow in the motor through a ventilation path outside the stator iron core inside the frame. It is confirmed that there was a flow separation where air did not flow along the path surfaces. This was observed in a flow visualization experiment using water instead of air. We propose a new structure to prevent air separation and confirm its effectiveness by a visualization experiment. It is also shown that another structure with paths both inside and outside the stator iron core in the frame improves the motors cooling performance. These structures are effective for EV motor downsizing

Small induction motor noise calculation

There has been an increasing demand for a quiet induction motor. Electromagnetic noise is jarring to the ear. Most offensive electromagnetic noise is generated when the natural frequencies of the stator coincide with or are close to the frequencies of the magnetomotive forces. Electromagnetic noise is calculated by BEM program using the electromagnetic forces of Maxwell stress. The natural frequency and behavior of the stator are calculated by mechanical FEM, considering the contact between stator core and frame. Spring elements are introduced between the stator frame and the pressed core. Vibration is calculated by mechanical FEM. Calculated and experimental noise level were within 3 dB(A) at 1,200 Hz and 4,080 Hz.

Bridge and rotor inductances of closed slots induction motor

In this paper, the bridge inductance of closed slot was investigated by a search coil, FEM analysis and conventional equations. The bridge flux density and the bridge linkage flux were measured with removed a closed-slot rotor of 4P-0.75 kW motor. The inductance was also calculated using magnetic energy and magnetic co-energy obtained by FEM.