The oil circulation rate of the rotary compressor is a crucial factor affecting the performance and reliability of air-conditioning systems-too much oil in the refrigerant-oil mixture causes poor heat transfer and early failure of parts; too little oil means excessive friction and wear of the journal bearing. In this paper, we show how finite-element analysis and topology optimization of a single-phase induction motor of a rotary compressor can be used to reduce the oil circulation rate to the minimum safe level. We analyze the nonlinear transient characteristics of the single-phase induction motor for the rotary compressor by using the program FLUX2D. We optimize the topology of the electromagnetic systems by using finite-element analysis. For validation, we have manufactured and tested optimized induction motors.