Open-circuit noise in synchronous machines

Multiphysics Modeling of a Permanent Magnet Synchronous Machine by Using Lumped Models

“…In theory, our model gives the maximum noise level at 2844 Hz. This is due to the excitation force link with the harmonics of teeth (f r ) associated with order (r) equal to zero (19) [32]. The analytical model gives different natural frequencies that are validated by the measurements in (Table I).…”

Analytical Prediction of Noise of Magnetic Origin Produced by Permanent Magnet Brushless Motors

“…The larger the magnetic force order, the lower the deflection of the stator core which is inversely proportional to the 4 th power of the force order [9]. The calculated noise level is usually lower than that obtained from laboratory measurements because calculations may not include all harmonic forces [16].…”

“…4), influence of magnetic saturation on the equivalent slot opening, damping factor, elasticity modulus of the slot content (conductors, insulation, encapsulation), higher time harmonics of the input current (inverter-fed motor), etc. All the above input data are difficult to obtain or predict with sufficient accuracy [7,16]. …”

Controlling airgap magnetic flux density harmonics in synchronous machines using field current injection

“…The method was tested by simulating a full-scale generator that emitted audible noise at f w = 700 Hz, it had been confirmed that the noise was due to Walker noise [24] that excited a mechanical resonance. The Walker noise arises due to interaction of permeance harmonics and rotor mmf.…”