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Magnetic flux density in induction motor

Accurately modeling the skewed rotor of an Induction Motor

Motors & generators with MagNet

Induction motors are one of MagNet's specialties. The induction motor analysed here is a typical three-phase motor, but MagNet modeling improvements have made it easy to include features that were previously ignored. The rotors of induction motors often have skewed slots to minimize torque ripple; this is now easily created and accurately modeled.

The stator windings in this model are realistic involute shapes, created with the multi-segment sweep option, which has powerful automatic blend calculations making the creation of these and other complex coil shapes easy. Accurately modeled coils means that end effects can be studied.

The periodic boundary condition allows the modeler to take advantage of symmetries; in this case, only a 60-degree section is modeled, reducing the problem size by a factor of 6.

Accurately modeling the skewed rotor of an Induction Motor

METHODS and RESULTS

STATOR INVOLUTE WINDINGS

A picture of half of one of the stator involute windings is shown on the left. Once this segment is created in MagNet, multiple instances of it can be imported with transformations applied in order to create the full set of stator windings. Possible transformations that can be applied to objects in Infolytica's software packages are scale, rotation, mirror and shift. Any number or combination of these transformations can be applied in our software.

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EASY DESIGN of INVOLUTE WINDINGS

To facilitate the design of 3D devices in our software, a feature, multi segment sweeps, was added allowing for the easy design of complex paths such as the involute shown above. The image on the the left is a snapshot of the dialog box associated with the involute winding.

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CUTAWAY VIEW of the INDUCTION MOTOR

An exploded view of the induction motor is shown here; parts of the motor are removed in order to see the windings and skewed rotor better.

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MAGNETIC FLUX DENSITY

This is an arrow and shaded plot display of the magnetic flux density. The rotor is not displayed in this field view, as only a slice through it is shown. Note the effect of the field on the stator due to the skewed rotor.

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MESH GENERATED in MAGNET

To the left is the mesh generated by MagNet for the induction motor with a skewed rotor. Because of symmetry, it is only necessary to model a 60-degree section of the motor. This is made easy by using the odd periodic boundary constraint available in all of Infolytica's software products. In the snapshot, some objects are removed so that the rotor and stator can be seen clearly. The complete mesh has 740 000 tetrahedra and 130 000 nodes.

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