Abstract: A cooling arrangement for a high speed open rotor reluctance motor/generator apparatus of the type finding combination use in aircraft applications for engine starting and electrical energy generation in both normal and auxiliary power unit operating conditions. The cooling arrangement identifies fluid flow alternatives which include inlet region redirection of coolant fluid to improve its induction into rotor interpolar space, rotor movement-induced centrifugal pressurizing of coolant using simple and more complex structural elements, machine heating of the coolant fluid, kinetic energy extraction from heated moving coolant fluid and combinations of these arrangements in particular machine configurations. Use of the invention under extremes of machine energy levels and self heating in military and commercial aircraft environments are contemplated.