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
