Fully Coupled Dynamic Model of Thomson’s Levitating Ring

Abstract

The complete electromagnetic-mechanical-thermal modeling approach is demonstrated on the Thomson's levitating ring experiment. This problem, but with a different set of parameters, was also described by Laithwaite and defined by Freeman and Lowther as TEAM17 problem. This paper presents its most complete solution. The factors for determining the vertical displacements and influence of the height of the ring are explained. The whole apparatus is explained in detail so that an accurate computer model can be made. The model introduced is validated against measurements and transient finite-element method (FEM) solvers. All the results prove the applicability of using steady-state FEM analysis with lumped parameter approach for a fast and effective fully coupled modeling.

Teaching Magneto-Thermal Coupling Using Thomson's Levitating Ring Experiment

“…In [17] the influence of the phase angle of the ring's impedance on the vertical displacement is presented. Nevertheless, the influence of the ring's height on the phase angle is only briefly elaborated.…”

“…Keeping the current in the coil equal throughout the measurements, if 2 w P is the measured real power with the levitating ring inserted and the 1 w P without it, we can determine the Joule losses in the aluminum ring as the difference in measurements is the effective value of the induced current in the ring. Using (17) and knowing the geometric and electrical properties of the ring together with its temperature, the current flowing through the ring is Excitation current in the coil has to be sinusoidal for the digital wattmeter used to be accurate. Therefore, we have to be in the linear part of the B-H curve of the ferromagnetic material of the core (i.e.…”

“…Finally, Fig. 13 shows the calculated resistance of the ring using (17) and Fig. 14 the calculated current flowing through the ring using (30).…”