This paper is dealing with the transient thermal modelling of high-speed asynchronous machines for helicopter using nodal method. The main goal of this work is to choose a nodal network structure for a generalized numerical tool aiming to precisely predict the thermal behaviour of high speed asynchronous machines at steady state as well as in transient mode, taking into account geometry variations of the machine, particularly stator and rotor pole numbers variation.In this paper the studied machine is a 29kW, 12000rpm high speed asynchronous motor including water cooling jacket.