A unified theoretical approach is presented to the calculations of the performance of the single-phase capacitor-start permanent-magnet (PM) ac line-start motor. Earlier work of S. S. L. Chang (1951) and of J. W. Finch and P. J. Lawrenson (1978, 1979) on capacitor reluctance motors is extended. A common set of reference frame transformations for steady-state, transient, and asynchronous performance is provided, permitting the use of the theory developed for the analysis of the balanced polyphase PM motor. A new approximate technique is given for estimating the average asynchronous torque/speed curve from computed acceleration curves.