1. General heat transfer laws

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 ).

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