Selection of the pole number of induction machines for variable speed applications

The selection of the pole number for induction motors supplied from a constant frequency source is straightforward because the pole number is determined solely by the synchronous speed required for the application. However, the selection of the pole number for inverter-driven induction motors is much more involved because the pole number is not determined by a single, dominating factor in these cases. In principle, any even number can be chosen as the pole number because the frequency can be adjusted and therefore the synchronous speed can be controlled to have any desired value. For these applications, the selection of the pole number typically involves numerous factors and trade-offs, many of which are identified and their influence on parameters and performance described in this paper. Some general conclusions on the selection of pole number are also presented