Various industrial electric motors use a combination of internal and external fans to remove internally generated heat. In recent years as the electrical efficiency of motors has improved, the power drawn by the cooling fans has become a large percentage of the total motor losses. This paper presents an optimization approach to the selection of the cooling fan dimensions. The design objective is to obtain minimum power input to the fans while maintaining adequate cooling capacity. To illustrate the method, the cooling fan design for a 30 hp, 3600 rpm, a-c motor is considered. The optimal fan dimensions result in a 70 percent reduction in fan power.

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