Constraints on saturation modeling in AC machines

The author presents constraints which must be satisfied by saturation models of lossless fields. Nonlinear terms are added to linear models to represent the saturation phenomenon. The major point is to emphasize that these nonlinear terms cannot be arbitrarily specified when lossless fields are assumed. This is done by returning to the fundamental laws which make up a typical dynamic model and showing that the traditional assumptions impose well defined constraints on the nonlinear terms. The constraints are derived from energy balance principles and must be satisfied by the flux linkage/current relationships in order to ensure consistency with the assumptions of a lossless field. The constraints are used to design a consistent saturation model for a synchronous machine