Comparison of different cooling fan designs for electric motors

Worldwide electric motor market is moving towards Premium/IE3, Super-Premium/IE4 and Ultra-Premium/IE5 efficiency classes. Therefore, motor manufacturers are constantly improving the overall design of three-phase asynchronous and synchronous motors and all the details with impact in the losses count, even if, individually, they just lead to efficiency gains of a fraction of a percentage point. In industry, most of the self-ventilated motors are driving unidirectional applications, such as fans, pumps, and compressors, and, therefore, the replacement of the typical bidirectional centrifugal fans of the external cooling system with a unidirectional axial fan may lead to a decrease in the acoustic noise and to a gain in the overall motor efficiency. In this paper, numerical simulations and experimental tests of different designs of axial fans and the respective comparison with the traditional centrifugal fans are presented. The tested axial fan prototypes were printed in plastic using a 3D printer. One of the novel axial fan designs led to a slight gain in the motor efficiency, maintaining the same operating temperature. That axial fan can be further optimized in order to require less power, have a better dynamic airflow, and produce less acoustic noise.