Numerical Simulation of the Flow and Temperature Field in a Rib Cooled Electric Motor

Realistic analysis of complex physical phenomena requires coupled simulation approaches. The integration of ANSYS for simulation of electromagnetics and fluid dynamics makes it possible to do real multiphysics calculations of electric machines. In a project between Anhaltische Elektromotorenwerk Dessau GmbH and CFX Berlin the cooling of an asynchronous machine for two loading points was investigated. Due to the encapsulated design of the motor the forced convection both inside the housing and on the outer cooling ribs had to be taken into account. Beside the rotational speed the distribution of ohmic losses was the main input parameter. These losses were built into the CFD model as heat sources in the stationary and rotating components of the machine. Because of the complexity of the windings it was in a practical sense not possible to describe them geometrically. Instead, porous media were used that also took the heat flux between solid and fluid into account. Measurements of velocity and temperature fields were carried out showing good agreement with the results of the simulation.