Abstract: A device and method for substantially enhancing the cooling of electric machines, e.g., motors and generators, is described. A hermetically-sealed chamber surrounds electric wire winding end-turns at either end of the stator core, and contains at least one phase-change coolant. The coolant removes heat from the stator winding through the end-turns, where often temperatures are the greatest, through cyclical ebullition, whereby heat generated by the stator winding end-turns boils and, subsequently, vaporizes the liquid coolant. The hot, vaporized coolant is removed through at least one vapor return passage and collects, cools, and condenses on the stator cooling jacket, which removes heat from the vaporized coolant. The liquid condensate precipitates into a wicking matrix, which continuously returns the liquid condensate through capillarity to the liquid coolant pool that partially wets the wicking matrix and winding end-turns.