Induction motor modelling-choosing the tool to do the job

Traditionally, induction motors have been modelled using one of two tools-the per-phase equivalent circuit and the two-axis model with pseudo-stationary rotor circuits. The former, which has entirely displaced its analogue equivalent-the circle diagram-has traditionally been used for steady-state calculations, and the latter for dynamic calculations. The computer revolution is changing all that. The now virtually limitless computer power has resulted in a blossoming of new computer-intensive models. The purpose of this paper is to pause, step back, and discuss when to use which.