The dynamometer test data (rotor speed, input current,
retarding torque, and rotor temperature) were recorded in
spreadsheet format using DAISYLAB utility software. Figs. 2
and 3 illustrate the torque characteristics of these machines
as measured on the torque dynamometer. Fig. 2 shows the retarding
torque versus current characteristics of the eddy current
machine at various rotor speeds (100–1000 RPM). Fig. 3 shows
the torque vs. rotor speed characteristics of these machines
at constant excitation current. It is clear that the relationship
between the torque and the rotor speed with the excitation
current held constant is not linear as has been assumed in [1].
This torque-speed relationship can best be described through a
quadratic function. Hence, a parametric model that captures the
basic torque-current relationship proposed in [1] but enhances
the torque-speed relationship through a quadratic function is
proposed in this paper. The following equation describes the
proposed model