This study presents results of modelling of heat transfer in low-power synchronous motors with internal permanent magnets (IPM). The analysis is conducted on the basis of equivalent thermal network as well as the magnetostatic finite element analysis for determination of usual electromagnetic loss components. The approach which consistently combines the two mentioned models allows for effective analysis of heat transfer in the machine at the designing stage. Special attention is focused on the method for homogenisation of a mush-wound winding and sheet stack. The results of computer simulations are positively verified by measurements carried out on the physical motor.