Optimum design of the stator parameters for noise and vibration reduction in BLDC motor

A new optimum structural design is presented here in order to shift the natural frequencies of the stator structure in brushless DC motor to the highest values at different mode shapes and increase the stator stiffness. Shifting the stator natural frequencies to higher values reduces or eliminates the severe effects of the structural resonances as the coincidence of the natural frequencies and the components of the motor electromagnetic excitation forces occur at higher frequencies at which the forces have lower amplitudes. In the proposed structural design, some parameters relating to stator slot are optimised to shift the stator's natural frequencies to the highest values without changing the slot areas and the stator outer diameter as the problem constraints. The optimisation is done by the response surface methodology combined with the modal analysis by the finite element method (FEM). The validity of the optimisation method is confirmed by FEM simulations and experimental tests at different speed regions. Moreover, the performances of the prototype and optimum motors are analysed by FEM and experimental tests to show that the stator parameters optimisation process does not cause any negative influences on the quality of the motor performance.