Virtual Torques (Magnetostatic)

Similar to the virtual force calculation, the system uses virtual work principles to compute the torque on an object. In the structure shown below, the torque on Object B about the axis of rotation is given by the following relationship:

where W(q, i) is the magnetic coenergy of the system. The current, i, is held constant.

Unlike the classical virtual work method, Object B is not actually rotated during the torque computation. Instead, only the triangles that lie along the outside surface of the object are virtually distorted. Thus, the change in the system’s coenergy (and therefore the virtual torque) is given by the change in the coenergy of these triangles.