Analytical solution for transient, diffusing fields inside a ring conductor with rectangular cross section

Comment on ‘Analytical solution for transient, diffusing fields inside a ring conductor with rectangular cross section’ [IET Sci. Meas. Technol., 2008, Vol. 2, No. 5, pp. 367–375]

“…Symmetry requires that the current density vector, and consequently also the magnetic vector potential, be vectors along the longitudinal direction, and the magnetic field intensity vector along the circumferential direction. Further, it will be assumed, as in [1], that the magnetic vector potential is independent of the azimuthal angle and varies only with the radius and time…”

“…Up to this point, the presented calculation algorithm is exactly the same as in [1]. At this point, VT gives the boundary condition on the external radius r = r 2 , (19) in the VT paper…”

“…In the paper in the title of this comment, V. Thiagarajan (VT) [1] derives analytical series solutions describing the diffusing field transients in a few milliseconds in a ring conductor with a rectangular cross-section. A linearly ramped or step voltage is imposed on one axial end of the ring conductor, whereas the other axial end is grounded and maintained at zero potential.…”

“…Second, the boundary condition on the external surface of the ring, (19) in the VT paper, is not correct. Finally, the results presented in [1] cannot be repeated for the full range of changes in model parameters by using Comsol Multiphysics finite element software [2], because the mathematical model is wrong.…”

“…Fig. 1 shows the physical model originally studied in [1], which will be re-analysed here. The inner and outer radii of the ring conductor, of length L in the axial direction, are equal to r 1 and r 2 , respectively.…”