Decrease of asynchronous rotation-frequence noise and vibration caused by electromagnetic force inside the motor for a hybrid vehicle

A hybrid vehicle (HEV) is one of the solutions to improve efficiency of a cruse and to reduce CO2 gas. 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. And according to electrical output up rating of a hybrid electric vehicle motor, parallel circuits will take place in the armature circuit. But it possibly causes trouble of noise and vibration of the motor because the motor driving systems of electric vehicle (EV) or HEV must operate at large variable speed ranges of up to 1:5. The authors analyzed the feature of noise pattern and consider the main cause. Mock up tests are conducted to confirm the main cause and the countermeasures including winding scheme change are determined. This paper describes mechanism of asynchronous rotation-fequence noise and vibrations arising from parallel circuit and the method to decrease them.