Equivalent circuit representation of a superconducting alternator

An equivalent circuit has been derived to represent the d and q axes of an air-cored superconducting alternator. The windings and screens in the machine are represented by the branches in the ladder-type network. The circuits have been used to obtain expressions for the damping coefficients and screening ratios during small oscillations. A modified screening ratio is proposed which differs from the conventional definition, but which is easier to apply to this type of machine. The circuits have been extended to permit an electrically thick screen to be represented by a number of layers, and the effect of the number of layers chosen, on the screening and time constants, is shown.