Computed tomography method of force calculation in electrical machines

A novel method is presented in which a two-dimensional image of the magnetic field in the air gap is created, while the machine rotates on load. The axis components of the field and the derivatives of the force distribution acting on the air-gap surfaces of the stator or rotor members can be determined accurately. Results of force calculations, showing a marked improvement in accuracy over those previously obtained from finite-element solutions, give the two-dimensional distribution of the Maxwell normal and tangential stress tensors acting on a salient pole member. The importance of the method can be gauged readily by its applicability not only to determine accurately the magnetic conditions in the air gap, but also to take full account of actual electrical circuit conditions at the terminal simultaneously with the rotational load dynamics of the machine