Application Catalog
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| 39 - Torque Analysis of a Three Phase Induction Motor Accounting for the
Skew <DP,TR> |
Overview
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An induction motor can utilize skew easily because the cage is constructed
by metallic casting such as die casting. The harmonic components of the
induction currents that do not contribute to the torque and the torque
variations caused by the effects of the slots can be reduced by applying
skew to the induction motor to form a sinusoidal wave of the magnetic flux
variations that link to the cage.
This example presents the use of a magnetic field analysis to obtain the
torque waveform of a three-phase induction motor with and without a cage
that has skew. |
Torque Variations
The torque waveform with and without skew is indicated in Fig.1 and the
size of the variations is indicated in Table 1. The results with skew are
obtained using a 3D analysis. The results without skew are obtained using
a 2D analysis. The results are also combined for the 2D analysis results
by the skew angle.
An induction motor produces torque from the rotating magnetic field of
the stator core and the induction current of the rotor. The torque variations
can be reduced by using a cage that has skew.
The torque ripple is reduced and the estimated amount of torque produced
by using a cage with skew that is combined in the 2D analysis results can
be obtained easily from the waveform accounting for each skew angle. |
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Current Density
The 2D current density versus frequency is indicated in Fig. 2 and the
current density distribution of the cage is indicated in Fig. 3.
The harmonic components of the current produced by the harmonic magnetic
flux in the stator are reduced by using a cage with skew as indicated in
Fig. 2. For this reason, the torque variations are reduced as described
previously. |
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Updated: 2011-02-28
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