Novel Blade-Shaped Rotor Hub Design for Electric Machine Cooling

This paper proposes a novel blade-shaped rotor hub structure for the cooling of electric machines. As the rotor rotates, blades in the rotor hub function as a fan that draws air from the ambient environment into the machine. Radial inlets and outlets are designed in the machine housing to direct the airflow over the end windings, stator, and rotor surfaces in order to provide cooling by forced convection. An interior permanent magnet machine is designed using this proposed rotor hub structure. The stress on the rotor hub is simulated using SolidWorks. Finite element analysis is used to evaluate electromagnetic performances. The fan curve of the rotor hub, pressure drops in the front and rear housing, and surface heat transfer coefficients are obtained using computational fluid dynamics simulations. The calculated surface heat transfer coefficients are used in a thermal analysis of the machine, and results show that the proposed machine can be effectively cooled using only the airflow provided by the proposed rotor hub.

I. Introduction

With the development of electrification in transportation, electric machines are required to provide high output power with limited volume and/or weight [1]. As the current density increases, thermal management plays a critical role in the machine design process. Temperature rise in the windings will increase copper loss and may reduce the winding insulation life. Cooling is particularly important to permanent magnet (PM) machines in order to prevent the demagnetization of the magnets. This paper proposes a novel blade-shaped rotor hub structure that improves rotor, stator, and end winding cooling and can be implemented in many machine topologies, ranging from induction machines to PM machines.