What are the main transfer paths of electromagnetic vibrations?

The following table summarizes the transfer paths of electromagnetically-excited vibrations in electric machines. Most common e-NVH issues arise due to transfer paths 1 & 2.

Transfer path of e-NVH
ID Circumferential wavenumber Force direction Nature Transfer path analysis
1 r>1 Radial, tangential Air-borne Radial circumferential deflection of the outer stator yoke and frame assembly, or of outer rotor (rotating in forced regime, pulsating at resonance).
2 r=0 Radial Air-borne Radial pulsating circumferential deflection of the outer stator lamination and housing assembly, or of outer rotor.
3 r=1 Radial (unbalance magnetic pull) Air-borne Bending / tilting deflection of the outer stator frame or outer rotor, in particular in clamped-free conditions and with eccentricities.
4 r=1 Radial (unbalance magnetic pull) Structure-borne Propagation of rotor bending vibration to rotor shaft line and gearbox mount, or bearing sleeves and outer stator frame.
5 r=0 Tangential (cogging torque / torque ripple) Structure-borne Propagation of rotor torsional vibration to rotor shaft line and gearbox mount, or bearing sleeves and outer stator frame.
6 r=0 Tangential (cogging torque / torque ripple) Air-borne Deflection of the outer stator yoke and frame or outer rotor following a unbalanced torsional mode due to particular boundary conditions.
7 r=0 Axial Air-borne Axial deflections of the end shields, especially when axial magnetic force harmonics occur due to skewing.
Transfer Path Analysis of electromagnetic noise & vibrations
Transfer Path Analysis of electromagnetic noise & vibrations

Read more