PURPOSE: To provide a highly reliable rotating electric machine which can be continuously operated even when its field winding is quenched and can be applied to business use, its cooling device, and generator operating method.

CONSTITUTION: A rotating electric machine is provided with a multiplexed field winding 11 constituted by connecting in parallel windings 1a-1z and it is preferable to use a superconducting material to form each winding 1a-1z. It is also possible to use such a superconducting conductor that can be realized in future and exert a superconducting property at a room temperature or a conductor having a conducting property which is close to a superconducting property to form each winding 1a-1z. The cooling device of the rotary electric machine is provided with a quench detecting means which detects the occurrence of quenching in the field winding and cooling capacity increasing means which transiently increases the cooling capacity of a liquid coolant when the quenching of the winding 11 is detected. A generator operating method is constituted in such a way that the quenching of the field winding 11 is detected and the voltage of a generator is controlled to a fixed level until the occurrence of the quenching of the field winding 11 is detected. When the occurrence of quenching is detected, the field current of the generator is controlled to a fixed level and, at the same time, the set value of the field current is lowered.