A Study on Design and Optimization of High Power Density PMSM for Pod Propulsion System

Pod propulsion systems are widely used in marine industry, since they exhibit high efficiency and reliability especially when they are combined with permanent magnet synchronous motors (PMSMs). A motor of this type can easily present high power density ratings in high-speed operation. However, when such a low-speed application is considered the achievement of high power density for the motor is not an easy task. Also, there is a large amount of constraints that have to be fulfilled. This paper deals with the effective design and optimization procedure of a PMSM with surface mounted magnets, which is going to be the propulsion motor of a passenger ferry. For this purpose, an appropriate objective function has been constructed and various constraints related with motor's dimensions, the maximum acceptable current density, the non-saturable operation and other practical aspects have been taken into account. Finally, the presented results are compared with others found in technical literature and reveal a quite satisfactory enhancement of motor's power density.