Alternative ways of cooling an E-Core Flux-Switching Permanent Magnet Machine with Large Air-Gap

The work presents two alternative ways of cooling a flux-switching permanent magnet machine with a large air-gap length of 3 mm. The investigations are based on a small power machine (D-Sa = 100 mm, 1=80 mm) which is designed for the needs of a special application where a defined clearance between the stator and rotor is required to ensure the working principle. The increased air-gap volume promotes the machine cooling from the stator inner surface by means of applying ordinary rotor (step) skewing technique for the salient pole reluctance rotor. In order to proof this cooling concept a test-setup is build up for thermal evaluation purposes. A more widely applicable approach for the thermal heat dissipation within the machine stator is also presented. In this case, the heat is directly extracted from the coil sides of the stator phase winding employing heat pipes. This totally passive cooling technique can improve the efficiency of all kinds of machines by keeping the phase resistance at lower levels or alternatively allowing an increase of current density in the slot without the need of additional cooling equipment like a fan, a radiator or a liquid cooling circuit.