A method is presented and validated for increasing the computational efficiency in simulating double-cage induction machines where stator transients are to be included. Iterative decomposition is used to separate the flux-linkage equations into decoupled fast and slow subsystems, after which the model order of the fast subsystem is reduced by neglecting the heavily damped fast transients caused by the starting cage. The two decoupled subsystems along with the equation for the very slowly changing slip constitute a three time-scale model for the machine which resulted in more than doubling computational speed.