[Objective] To address the challenge that the traditional lumped-parameter thermal network (LPTN) struggles to characterize the temperature gradient between the winding insulation layer and impregnating varnish, this paper proposes a transient temperature rise calculation method. This method couples conformal mapping with an LPTN to analytically derive the equivalent thermal conductivity of the windings. [Methods] Firstly, a 10 kW surface-mounted permanent magnet synchronous motor was taken as the research object. The conformal mapping method was utilized to transform the arc-shaped isothermal boundary of the copper conductors into a straight-line boundary, thereby mapping the complex non-uniform thermal field inside the winding into a flat-plate thermal field, and the equivalent thermal conductivity of the winding was solved analytically. Then, an equivalent thermal network model was constructed based on the obtained equivalent conduction thermal resistance of the winding, and the copper loss was iteratively updated by considering the influence of the winding resistivity changing with temperature. Finally, the reliability of the analytical model was verified by comparing with finite element analysis (FEA) and temperature rise experiments. [Results] The simulation and experimental results showed that the error between the LPTN and FEA for the winding temperature rise was 1.94%, which proved the high calculation accuracy of the thermal network model in predicting the winding thermal characteristics. The errors between the LPTN model and FEA/experimental results for housing temperature rise were found to be 3.20% and 6.56% respectively, which further validated the effectiveness of the proposed model.[Conclusion] The winding homogenization modeling method based on the conformal mapping method proposed in this paper can effectively reflect the thermal characteristics of the winding while ensuring the calculation efficiency, and can be extended to the thermal analysis of other motors. In addition, the analysis of the influence of the stator inner and outer diameter ratio on the transient temperature rise of the motor shows that the transient temperature rise of the motor can be effectively suppressed by reasonably allocating the proportion of copper consumption and iron consumption.