Definition

In e-NVH, stator winding force harmonics (sometimes called stator mmf force harmonics, or armature field force harmonics) refer to Maxwell force harmonics linked to stator magnetomotive force space harmonics combined with slotting effects.

As magnetic noise and vibration frequencies are the same as the ones of magnetic force frequencies, stator winding harmonics can also refer to some specific harmonics of the acoustic noise spectrum or vibration velocity spectrum.

Winding force harmonics should disappear when the machine produces a sinusoidla magnetomotive force.

Application to e-NVH

In induction machines at no-load, winding harmonics may produce low wavenumber magnetic forces resulting in high e-machine noise and vibration levels.

In permanent magnet synchronous machines, fractional winding may produce low wavenumber magnetic forces resulting in high e-machine noise and vibration levels.

In spectrograms winding harmonics appear as straight lines crossing the origin.

Noise control actions

The key design parameter to control stator winding harmonics is the winding connection matrix itself. Increasing the number of slots per pole per phase reduces mmf space harmonics. The choice of the winding coil pitch / coil throw is also important but it has no influence on the stator mmf stepped harmonics of wavenumber Zs+/-p. Going from fractional to integral winding in PMSM also drastically reduces the effect of winding harmonics.

Application to Manatee

Manatee software electromagnetic models account for all winding space harmonics. Any type of winding can be modelled. A parameter sweep can also be run directly on the winding coil pitch of the machine.