When the electric motor is in full operation, its temperature increases and can reach an external temperature of 80º to 90º, but even then they work perfectly, without their characteristics being affected, as this heat is dissipated to the external area.
The ambient heating where the engine is installed is related to the heat dissipation and not to the temperature of the casings. This temperature will also depend on the number of motors that are installed and working in the same environment.
An electric motor with cold housing may have greater losses or greater heating of the windings than a hot engine.
Irregular surfaces cause poor contact and inefficient thermal conduction. When the coils, stator and housing are in contact with each other without void spaces, there is good heat transfer. This heat generated by them will be dissipated out in the best possible way, and this will depend on the thickness of the carcass and various other factors.
When there is air accumulation, direct contact between the engine parts is prevented, we will have a poor heat transfer. The engine casing may be cold on the outside, but inside it will be so high that it could damage the engine. https://www.mrosupply.com/ac-motors/severe-duty-motors/701974_cecp84115t-5_baldor/