A Hybrid Vehicle (HEV) and an Electric Vehicle (EV) are some of solutions to improve efficiency of a cruse and to reduce CO2 gas by regenerative breaking and operating the engine in optimum condition. It is requested to decrease the motor size and to increase the maximum torque for minimizing the driving units. For these purposes permanent magnet applied motors have been commonly used recently. The motor driving systems of HEV or EV must operate at variable speed ranges of up to 1:5. For this large range, Silent and smooth operations are desirable and important. Skew method is often adopted to ensure smooth start and stop and silent operation by reducing the torque ripple. But it possibly causes noise and vibration of the motor. This paper describes the mechanism of torsional resonance noise and vibrations arising from the skew method and the countermeasure to decrease them. Noise and vibration frequency and vibration mode were measured to identify the root cause of the noise at low rotating speed range from 3,000rpm to 4,000rpm in generating operation. Through this measurement and rotor skew phase optimizations, the root cause was identified to be the resonance between axial torsional natural frequency and electromagnetic force of slot ripple. Current design has conventional half slot skewed permanent magnet rotor. Rotor skew phase in the rotor was changed to 4-step V skew. After adoption of this countermeasure, the large and plateau noise around 3,000 rpm to 4,000 rpm were disappeared. This shows effectiveness of the adopted countermeasure. This method is applied to a large electrical output and large variable speed range permanent magnet reluctance motor (PRM) for the final advanced motor design. After large improvement in noise, the PRM are applied for a hybrid SUV, a passenger car and a hybrid truck now.
Torsional resonance noise reduction by motor torque phase adjustment
EVS, Electric Vehicle Symposium, 26 ; 1242-1247
2012
6 Seiten, 13 Bilder, 15 Quellen
Conference paper
English
Permanent Magnet Motor Torsional Resonance Noise Reduction by Rotor Skew Phase Adjustment
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