To realize a rotating electric machine small-sized and light-weight for an output required by building a map of a rotational speed and a protecting temperature preset in a temperature control flow, determining a temperature protection set value automatically on occasion, and performing comparison with a coil end temperature signal and performing heating protection.

As temperature detecting means for a synchronous motor for electric cars, a thermistor sensor 12 is fitted to a stator coil end, and another thermistor sensor 13 is fitted to a spot near the rotor of the end surface of a stator core. Besides, a temperature protection set value is automatically determined on occasion, by building-in a map of the rotational speed and a protecting temperature beforehand, and taking in a rotational speed signal of a rotating electric machine. And heating protection is performed by comparing this set value with a coil temperature signal from a temperature detecting means fitted to the coil end of the rotating electric machine. Here, the rotational speed- protecting temperature map is set from temperature increase data etc., at each rotational speed, and the difference between limit values at individual parts is taken into consideration.