Summary

EMSolution allows the user to specify the motion of an external current field source (COIL) during motion analysis (MOTION=1). In this case, you can specify both translational and rotational motion, but the manual is not clear on how to do this. Therefore, we supplement it here.

Explanation

First, prepare a local coordinate system whose z-axis is the axis of rotation to be analyzed and specify it by COORD_ID (0 is fine if it matches the z-axis of the global coordinate system). Next, specify the time variation of the rotation angle around the rotation axis from the COIL definition position in PHI_TIME_ID. If the COIL moves while rotating, specify the translational motion in overall coordinates X_TIME_ID, Y_TIME_ID, Z_TIME_ID.

The axis of rotation of COIL moves in parallel with this translational motion. In terms of coordinate transformation, the rotation is done first with respect to the COIL coordinates, followed by the translation.

Fig. 1 shows an example of a circular coil (LOOP) being moved in the z direction while rotating around the y axis. The blue position is the initial position of the coil definition. Although the analysis is only performed for static magnetic field analysis, the motion can be given in the same way for transient analysis involving eddy currents.

Fig.1　Analysis including rotational translation of the coil
(Magnetic flux density arrow diagram)