Current Harmonics, Torque Ripple and Whine Noise of Electric Machine in Electrified Vehicle Applications

Noise and Vibration (NVH) characteristic of an electric machine (e-Machine) is the outcome of complex interaction between source level disturbances and the surrounding structure to which the e-Machine is attached. Key e-Machine metrics that objectively quantify source level disturbance include torque ripple and radial electro-magnetic forces. These disturbances can radiate directly from the e-Machine housing (air-borne component) and also can be transmitted through the structural attachments like stator bolts, stator ring, powertrain mounts etc. (structure-borne component). In the e-machine driven by PWM switching inverter, current is not perfectly sinusoidal but contain different level of harmonics. Current harmonics impact Torque ripple, which in turn would translate into undesirable noise and vibration. There is very limited literature referencing the influence of current harmonics on torque ripple and e-machine NVH. This paper specifically addresses the impact of current harmonics on the 6^th and 12^th electrical orders of the torque ripple and relevant e-Machine whine noise employing statistical correlation & regression analysis based on the data sets acquired from dynamometer testing and finite element based CAE calculations.