Quantification of NVH Parameters in DC Electric Motors Used for Automobile Application

With growing demand of comfort of cars, number of small electric motors used for adjustment of different functional units is steadily increasing. Due to the various rotational components and the forces they accord, electric motors radiate significant amount of noise at high frequencies with tonal components that can be annoying.

Motor noise comprises three sources namely: electromagnetic, aerodynamic and mechanical. This study considers mechanical and electromagnetic sources of Electric Power Assisted Steering (EPAS) motor used in passenger cars.

This paper describes an approach to assess noise and vibration parameters between field motors and fresh motors. Noise and vibration spectrums are analyzed in terms of frequency contents and dominancy of mechanical sources in sound power radiated by motor is discussed. FE modal analysis of motor is performed and correlated with impact hammer measurements to quantify structure borne energy contribution. Noise and vibration of motor is analyzed to identify structure contribution. Finally improvement is suggested to reduce structure contribution and its effect is discussed.