Structural Vibration and Acoustic Analysis of a 3-Phase AC Induction Motor 2019-01-1458

This paper is aimed at studying the NVH and acoustic performance of a 3-phase AC induction motor in order to find a way to reduce the magnetic component of noise from an electric motor in an electric vehicle (EV). The method suggested here is to reduce the magnetic component of sound from the motor by making modifications to the end bracket of the motor housing. EVs are being considered the future of mobility mainly owing to the fact that they are environment-friendly. With a lot of companies already investing heavily in this technology, electric drives are set to become extremely popular in the years to come. The heart of an EV is its motor. Modern electric vehicles are quiet and with the lack of an IC engine to mask most sounds from other components, the sound from the electric motor and other auxiliary parts become more prominent. This paper lays down a process to analyze the sound radiated from the electric motor in three broad steps. First, to model the motor in an electromagnetic platform, Ansys Maxwell in this case, and solve for electromagnetic forces. Second, to perform a modal analysis on the motor and identify resonant frequencies after which the electromagnetic forces need to be mapped to the structure. Finally, the structural displacements need to be imported to an acoustic platform, LMS Virtual.lab in this case, to perform an acoustic response analysis. The main source of electromagnetic noise in a motor arises from magnetic flux variations in the air gap which interfere with the resonant frequencies of the stator core. These flux variations result in a time-varying force that acts on the stator core or teeth and causes it to deform. This paper will talk about the radial and tangential components of this force and how these structural vibrations can be dampened by using a modified end bracket with properties that can help reduce the overall sound radiated by the motor.