New ventilation cooling for modular PM machines utilizing flux gaps and rotor ducts

This paper investigates a new ventilation cooling technology for modular permanent magnet (PM) machines. Air is pumped into the stator flux gaps and rotor ducts. A significant temperature reduction for the modular machines can be observed by introducing ventilated air. The flux gaps within the modular machines provide extra coolant path, notably modify the flow profile. Moreover, the flux gaps also provide additional contact area between machines and coolant, improving heat transfer rate. Comparative study between different machine configurations, including different inlet and outlet areas, different topologies of shaft, and different stator topologies have been investigated. Their influences on machine cooling have been investigated using computational fluid dynamics (CFD) modelling. Furthermore, since the coolant (air) will pass through the stator-rotor annular gap, i.e., airgap, as well as rotor ducts, the rotor speed will influence the cooling efficiency of the ventilation cooling system. This influence comes from shock loss, friction loss, and combining flow phenomenon. A series of experiments have been conducted to validate the CFD simulations.