One of the important characteristics of electric motors is the noise they emit during operation. This master's thesis deals with the analysis of noise from a series-produced electronically commutated (EC) synchronous electric motor with permanent magnets mounted on the external rotor. With the motor under consideration, we detected disturbing noise at certain rotational velocity within the motor's operating range. Initially, we conducted experimental measurements to assess the impact of changing pulse width modulation (PWM) control parameters on the motor's noise. It was determined that this approach does not influence the motor's noise. Subsequently, through experimental measurements of sound pressure during motor startup, we identified that the elevated noise was caused by the resonant frequency of one of the motor's components. This critical frequency, at which the undesired noise occurred, was further identified and connected to the EM rotor through experimental modal analysis. In continuation, we employed numerical modal analysis to investigate the influence of components on the rotor's inherent dynamics. Using numerical analysis, we generated a set of design solutions aimed at altering the rotor's resonant frequency sufficiently to avoid resonance phenomena. We found that through a straightforward rotor design change, complete mitigation of disruptive noise throughout the motor's operational range is not achievable. However, it is possible to shift the critical point at which this noise manifests by doing so.
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