Characterisation of radial vibration force and vibration behaviour of a pulse-width modulation-fed fractional-slot induction machine

The authors present the full analysis of the vibration behaviour responsible for audible magnetic noise in a pulse-width modulation (PWM)-fed fractional-slot induction machine, including theoretical predictions, numerical simulations and experimental validations (stator modal analysis and deflection shapes visualisation). Magnetic force waves caused by slotting harmonics, PWM harmonics and their interactions are characterised in terms of nodes number, rotation speed and propagation direction. It is shown in particular that some odd spatial order vibration waves appear because of fractional slotting, and that some combinations between slotting lines and PWM lines can be very noisy because of an elliptical mode natural frequency close to the switching frequency. Nomenclature