The subject of the paper is a three-dimensional analysis of a coupled fluid-thermal and electromagnetic field in permanent magnet synchronous machine that can work at very high temperatures. To obtain the distribution of the airflow and temperature we employed the coupled fluid-thermal model of the machine. This allowed us to check whether the temperature in sensitive elements does not exceed the permissible limits. The analysis took into account the effect of the color and the smoothness of the machine housing on the temperature distribution in its interior. The influence of design on the temperature distribution and distribution of hot spots was tested. Two topologies are studied considering magnet mounted on the rotor surface or buried in the rotor soft magnetic core. The simulation results were compared with measurements made on a prototype.