A partially decomposed variable-order model of the double-cage induction machine is presented and validated. The model exhibits improved computational efficiency in simulating full machine behaviour including stator transients. A state variable transformation is used to separate the electrical steady-state from the transient part of flux linkage response. The transient flux-linkage response is next decomposed into fast and slow sub-systems which constitute the boundary layers of the overall model. The fast subsystem is then reduced by neglecting the heavily damped fast transients caused by the starting cage. Each of the two decoupled boundary layer equations may be computed using different time steps and even ignored during periods when the corresponding mode is not excited, thereby effectively reducing model order and greatly decreasing computational requirements while retaining simulation accuracy.