Rotating electrical machines - Simulation of thermal behavior

The operation of a rotating electrical machine is strongly conditioned by its external environment and manufacturing method. Ambient conditions (temperature, humidity, etc.) fluctuate greatly depending on the motor's use. More or less sudden fluctuations in load can lead to overheating, which is particularly harmful to sensitive machine parts. These may include winding insulation, bearing housings, commutators (DC machines) or even magnets (permanent magnet motor inductors). With the advent of new power supplies and increasing power densities, it is essential to be able to predict the thermal behavior of these machines as accurately as possible.

Developing a thermal simulation tool requires quantifying, separating and locating the various internal heat sources that generate heating. This aspect, like boundary conditions (flux and/or temperature), can only be taken into account through experimental phases. Validation of such numerical tools requires a good understanding of the machine's internal transfer modes. The three fundamental modes must be taken into account when performing detailed thermal analyses. They can, however, be taken as a whole for more applied and less fundamental studies. However, it is essential to know all the thermophysical parameters specific to the machine under study (densities, mass heat capacities and conductivities).

The numerical analysis methods most commonly used were initially nodal methods. These are now being replaced by more global methods such as finite element analysis. The latter is a fast-growing method, frequently developed on a thermal level. One current development is its weak or strong coupling with electrical and/or magnetic problems. Similarly, on the thermal side, processes coupling conductive, convective and radiative problems are being considered using finite elements, although they have already been carried out in global form (flux conservation) using older nodal methods. Finally, to conclude this introduction, the dynamic behavior of motors is currently being taken into account using finite elements.