General heat transfer laws
Refroidissement des machines électriques tournantes

The various sources of heat generated by an electrical machine are evacuated by means of three transfer modes (figure 1):

• heat transfer by conduction in the machine structure ;

• heat transfer by radiation between each of the structure's walls and the environment;

• heat transfer by convection, external or internal, natural or forced, depending on the cooling technology employed. Two main types of machine can be distinguished in terms of cooling technology: closed machines (figure 2) and open machines (figure 3).