8 – Analysis of an Axial Gap Motor

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Application Note / Model Data


Unlike typical cylindrical motors such as radial gap motors, axial gap motors have a structure in which the stator and the rotor, which is arranged on a disk, face each other and produce rotation. For that reason, because it is possible to arrange thinner parts than with a radial gap motor, they can respond to demands for miniaturization of equipment.
With axial gap motors, evaluations using the magnetic circuit method and empirical data are difficult because the magnetic flux that passes through the rotor and stator, which face each other, becomes a 3D magnetic circuit, meaning that a 3D electromagnetic field simulation using the finite element method (FEM) is necessary because it can carry out an accurate analysis.
In this example, how to use JMAG’s 3D magnetic field analysis to carry out a load analysis of an axial gap motor, and then obtain the Torque-Speed curve and the Torque-Current curve.

Magnetic Flux Density Distribution

The magnetic flux density distribution at a rotation speed of 1,000 r/min is shown in Fig. 1. The axial gap motor has magnetic flux density distribution in the rotor coil’s rotation axis direction because of its structure. It is also apparent that the magnetic flux density is greater in the vicinity between the magnetic poles. High magnetic flux density causes magnetic saturation, which can lead to a decrease in torque.

Torque-Speed Curve/Torque-Current Curve

Fig. 2 and Fig. 3 show the analysis results for the Torque-Speed and Torque-Current curves, respectively.
The axial gap motor torque decreases as the rotation speed increases, and increases as the current increases.

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