What is tooth modulation effect?

Definition

Mechanical slot modulation effect, also called tooth sampling effect, is the fact that airgap magnetic stress waves are "sampled" when converted to physical magnetic forces applied to stator teeth. Consequently, due to Shannon theorem, the maximum stress wavenumber seen by the stator yoke is given by Zs/2 (half the number stator slots).

Application to e-NVH

This example illustrates in a 12s10p Permanent Synchronous Machines the sampling effect of the fundamental stress wave (r=2p=10) in an equivalent stress wave of wavenumber r=-2: GIF - 910.3 kb

In EV HEV NVH applications, for instance in a Zs=48 stator slots p=4 pole pairs PMSM, Maxwell stress waves of wavenumber r=11p+p=13p-p=12p=48 (interaction of 11p/13p rotor field harmonic with fundamental field) are experienced as pulsating forces.

Application to MANATEE

MANATEE software specialized in the e-NVH simulation of electrical machines and noise reduction of electric motors includes slot modulation effects.

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