Claw-Pole Alternator

This model showcases the automatic current distribution calculation feature of MagNet. The device is a Claw-Pole automobile alternator with a three-phase output winding on the stator. A field coil around the rotor core is used to induce flux in the output windings as the rotor spins.

Results

The 3D analysis model consists of a 60 degree section comprising one rotor pole pitch pair. The stator windings were created using the multi-segment sweep feature of MagNet. A boolean intersection was performed to cut off sections of the coil passing through the two symmetry planes. The current distribution is automatically calculated using the tetrahedral mesh of the coil segments. A periodic boundary condition linking these two planes ensures that the computed current distribution will flow in through point A, out through B, in through C and finally out through D on its way back to A again.

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The mesh of the 60 degree model in the aligned position appears on the right. The enclosing air region has been omitted for clarity. The two symmetry planes are matched with an even periodic boundary condition. The complete mesh has approximately 410,000 tetrahedra and 70,000 nodes.

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This is an arrow and shaded plot of flux density for the rotor rotated by 20 degrees from the aligned position. Note that the periodic boundary condition is applied to non-planar surfaces in this case (the air gap between the rotor and the stator).

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This graph shows the flux linkages of the stator coils at different rotor positions. The flux linkage in any one coil will complete a cycle every 60 degrees of rotor rotation. Since there are six coils in the section actually modeled, the complete waveform can be constructed by only solving at rotor positions between 0 and 10 degrees.