Abstract
Electromagnetic noise in Electrical Machines (EMs) occurs due to vibrations caused by magnetic forces acting onto rotor and stator surface. This is the dominant source for the considered permanent-magnetic excited synchronous machine in this paper. The radiated electromagnetic noise is sequentially calculated by a Finite Element (FE) and Boundary Element (BE) computation. An electromagnetic FE model is created to determine magnetic forces. Structure-borne sound and rotor dynamics are calculated using a structural dynamic FE model for the EM housing and the rotor. In order to predict resonance frequencies and amplitudes as reliable as possible, it is important to know the direction-dependent stiffness of the laminated rotor stacks and mechanical joints as well as their structural damping. Thereby, the properties of the laminated stack can be determined experimentally by a shear and dilatation test. Mechanical joint properties can be modelled by Thin-Layer Elements (TLEs) and the overall damping by the model of constant hysteretic damping. The radiated sound power is determined by a direct BE computation. The influence of dynamic rotor eccentricity on radiated sound power is examined for a run-up of the EM. All FE models are verified by data from experimental modal analysis.
Highlights
Introduction and aim of this workAcoustical noise of electrical machines is made up of three different types of sources: electromagnetically, mechanically and aerodynamically excited vibrations/noise [16]
Most of them are only related to structure-borne sound / vibration analysis (FE for electromagnetics & structural dynamics) and sound radiation of the machine housing caused by electromagnetic force excitation on stator teeth, cf. [10, 22]
Available works are based on analytical rotordynamic models with one or a few degrees of freedom or Finite Element (FE) models built up by beam elements, cf. [1, 21] and named references in [21]
Summary
Acoustical noise of electrical machines is made up of three different types of sources: electromagnetically, mechanically and aerodynamically excited vibrations/noise [16]. Most of them are only related to structure-borne sound / vibration analysis (FE for electromagnetics & structural dynamics) and sound radiation of the machine housing caused by electromagnetic force excitation on stator teeth (with/without eccentricity effects), cf [10, 22]. No publication has been found by the authors which considers the numerical computation of rotor dynamics due to distributed electromagnetic forces on the laminated stack (from magnetic FE analysis) using three-dimensional (3D) structural solid FEs. Available works are based on analytical rotordynamic models with one or a few degrees of freedom or FE models built up by beam elements, cf [1, 21] and named references in [21]. The influence of rotor eccentricity on sound radiation is examined
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