Topology Squirrel Cage Induction Machine (SCIM)
Model Types Permeance / mmf electromagnetic model (WFM)
Quantities Maximum sound power level during run-up (SWL)
Geometry NA
Winding NA

The objective of this validation case is to study the effect of skewing on the maximum sound power level calculated during a run-up from 10 to 3500 rpm, and compare the optimal skew value with the theoretical one of one slot pitch.


Manatee model for SCIM_008
Manatee model for SCIM_008


Sound powel level during ramp-up as a function of skew
Sound powel level during ramp-up as a function of skew

One can see that the rotor skew (linear slot inclination) effectively reduces the overall noise level. The optimal skew is here expressed in stator slot pitch. As there is 36 stator slots and 28 rotor slots, a rotor slot pitch equals 36/28=1.28 stator slot pitch. The minimum value found in MANATEE is also close to 1.28 stator slot pitch.

The optimum skew angle is defined with respect to a particular harmonic magnetic force wave. If the sound power and vibration levels are fully controlled by a single force harmonic, it is possible in theory to fully cancel vibration and noise. In this example, the minimum SWL is not 0 but close to 40 dBA due to discretization errors (number of skew slices) and the presence of other magnetic force waves.

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