Determination of optimal thermal parameters for brushless permanent magnet motor design

This paper describes the use of computational fluid dynamics (CFD) and lumped-circuit analysis in the optimisation of brushless permanent magnet servo-motor thermal design. As CFD is time consuming for data input and has long execution times a transient lumped-circuit package was developed to speed up the design process. CFD data relating to convection heat-transfer from various types of housing and flange mounted cooling plates has been used to formulate algorithms suitable for inclusion in the lumped-circuit model. This work has been used to-develop a range of servo-motors having improved torque per unit volume. This is achieved firstly by maximising the natural convection cooling using a radially finned housing. Secondly, the thermal resistance between winding and housing is minimised by the correct choice of internal dimensions and materials.