The transportation industry is facing various new technological changes. Among them, the replacement of traditional internal combustion engines by electric powertrains makes new vehicles quieter. Still, new challenges in noise and vibration are rising, in particular during the design of electric motors. In order to develop efficient architectures meeting the expectations both in terms of performance and acoustic comfort, engineers need to access new methods and tools.
Motor design generally starts with the torque as the main purpose of an electric motor is to deliver the required torque at a given speed range. Then, the dimensions of the motor start becoming apparent and efficiency analysis, radial force analysis, structural analysis, and acoustic analysis enter the loop.
“Acoustics analysis should be part of the process and not applied at the end of it” explains Dr. Berker Bilgin, Research Program Manager and Chief Engineer of Canada Excellence Research Chair in Hybrid Powertrain program at McMaster University. If not, it will become difficult to reduce acoustic noise from the motor once the motor design is finalized. Electric motor noise is mainly due to the impact of electromagnetic radial forces (see Figure 1) that excite the stator structure.
By including Actran in their design process, McMaster researchers developed current control techniques to limit acoustic noise: “Without making any changes in the motor we can actually reduce the acoustic noise just by optimizing the current, because the radial forces are also related to stator excitation, and we experimentally verified drastic noise reduction in switch reluctance motors”, said Dr. Berker Bilgin.
The use of simulation tools has reduced significantly the cost of prototyping and allowed a more advanced analysis of the designed product. Another added value of simulation is of course the attention paid to details thanks to 3D acoustic modelling capabilities. In addition, Actran’s visualization capabilities offer a great possibility for students to train and dig deeper in their research.
In the future, CERC in Hybrid Powertrain team plan on working on how to modify the structural modes without affecting the torque performance of the motor, focusing on current controls of the motors, or modelling the damping ratio of the motor for accurate estimation and reduction of acoustic noise in electric motors.