This paper deals with a 3-D development of a thermal model of a power electronic converter mounted on the generator shaft and rotating with it. The dimensions of the heat sink are determined, and the temperature gradients of the converter, its heat sink, and shaft during natural and forced convection are analyzed for variable rotor speeds. It is shown that the chosen sizes of the insulated gate bipolar transistor (IGBT) and the heat sink offer a compact design of the rotating converter, which is sufficient for its mounting in limited space offered by the generator shaft. Furthermore, a transient temperature profile is also presented. In addition, a transient thermal profile of the converter and dimensions of the cooling fan are also calculated. Besides, the analysis of the cooling requirements of the converter during over-currents due to grid faults is also investigated.