BASIC PRINCIPLE AND DESIGN CRITERIA OF AXIAL-FLUX PM MACHINES HAVING COUNTERROTATING ROTORS

Axial-flux PM machines are particularly suitable for application in el ectrical drives devoted to ship propulsion, since they allow the elimi nation of the large-power gearbox used in conventional systems, In con sideration of that, this paper deals with a novel slotless axial-flux PM machine topology which is characterized by the synchronous counterr otation of the two machine rotors, Such a new machine topology can fin d application in the direct driving of two counterrotating propellers, which may be used in ship propulsion systems to recover energy from t he rotational how of the main propeller slip stream, In this case, the use of an axial-flux machine having counter-rotating rotors allows an improvement in terms of weight and efficiency, since the epicyclic ge ar otherwise required for the motion reversal can be avoided, The pape r discusses the stator winding arrangement which allows the opposite m otion of the machine rotors and reports experimental results taken fro m a small-size machine prototype.