Reduction of force exciting influences to decrease radiation of acoustic noise in synchronous machines
Purpose - The paper aims to provide an approach to actively decrease the radiation of acoustic noise in synchronous machines. Design/methodology/approach - Splitting regular three-phase windings of synchronous machines into two independent three-phase systems allows for an active influence of the current waveform if both winding systems are mutually displaced against each other. The harmonics content of each phase-current varies due to the mutual inductive coupling with participating currents of both systems. Therefore, the ensuing force-density distribution on the stator teeth varies accordingly. Resulting structure dynamics and furthermore the radiation of relevant harmonics of the acoustic noise are based on the mechanical excitation of considered force-density distributions. Findings - Configurations of mutual displacement of phase windings of both winding systems with significant decrease of mechanical deformation and emitted acoustic noise are found. Simulation methods to entirely describe and prove the behavior described are developed. Research limitations/implications - The proposed approach is developed for a particular synchronous machine. Other machine types are conceivable for analysis in the same manner. Tools need to be adapted. Universal and reliable statements regarding acoustic behavior depend on the mechanical restraint of the machine and may therefore vary. Practical implications - Active force-density distribution is used for the noise reduction of alternators in vehicle applications. Additionally, wind-power generators are considered for the application of split stator winding systems to actively counteract inhomogeneous force distributions on the rotor, evoked by stalling of the propeller blades during pole passing. Originality/value - Active force-density modification by stator winding modifications allows for the decrease of noise radiation of electrical machines with rotating-field windings. Innovative simulation methods developed may now replace prototyping partially.
electric machines noise control