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Nonlinear Time-Transient in Switched Reluctance Motors (T.E.A.M. Problem 24)

Motors and Generators with MagNet for SOLIDWORKS

This is a test rig configuration similar to a switched reluctance machine. It is made of solid medium-carbon steel and mounted in a nonmagnetic cage which can rotate about a stainless steel shaft. This is a nonlinear transient problem, which was simulated using MagNet for SOLIDWORKS transient solver.

Each stator pole has a 350-turn coil around it, and the rotor is fixed at 22 degrees relative to the stator. A search coil is wound around a rotor pole to measure the total magnetic flux, and a Hall probe measures the y-component of the magnetic flux density at a specified position in the air gap between rotor and stator. Finally, a piezoelectric transducer measures the torque on the rotor.

Using MagNet for SOLIDWORKS' Transient 3D solver, the current, torque, rotor pole flux and the air gap point flux density are calculated.

The following is based on the Testing Electromagnetic Analysis Methods (T.E.A.M.) problem #24: Nonlinear Time-Transient Rotational Test Rig. The benchmark can be found on the International Compumag Society's website.

Test rig steel and mounted in a nonmagnetic cage

METHODS and RESULTS

DEVICE MODELING: MESH

The meshing needs to be properly refined in the region of the air gap between the stator and the rotor. This refinement ensures accurate prediction of the flux density field necessary for the torque calculation. MagNet for SOLIDWORKS' layer meshing was used on the top face of the rotor.

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COMPARISON OF THE ROTOR'S TORQUE

The data obtained is well in agreement with the experimental values included in the problem definition.

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MAGNETIC PLOT AT STEADY STATE

Here is a plot of the steady state (0.3s) magnetic field on the surface of the X-Y plane of the model. The highest magnetic field strength is obtained at the two corners of each rotor pole where they are the closest to the stator.

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COMPARISON OF THE FLUX DENSITY

The point of interest is located just off the surface of the rotor pole front face and the measured vs simulated flux density results are compared.

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COMPARISON OF THE ROTOR POLE FLUX

As explained in the problem definition, a search coil is used to measure the rotor pole flux. The same method was used for the study of this problem. In MagNet for SOLIDWORKS, a flux linkage quantity is available for every coil in a model and it was used here to obtain the total magnetic flux.

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INDUCED CURRENT PLOT

Proper induced current calculation is necessary in transient magnetic field problems like this one. Here is a plot of the induced current in the middle of the stator and the rotor. Higher induced currents are observed on the side faces of the stator pole closest to the rotor pole.

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