An alternating current motor comprising a combination of magnetic frequency tripler and induction rotor. The alternating current motor includes a three-legged core of which two legs serve as input leg having a coil wound thereabout and thereby constitute a linear reactor and a saturated reactor. The two coils are connected in series. The residual one leg serves as output leg which generates magnetic flux having tripled frequency by applying single phase input to the input legs. A rotor is rotatably disposed in the cylindrical gap formed in the output leg. Thus, the rotor is stably rotated at a higher rotational speed equivalent to synchronized speed determined by tripled frequency relative to frequency of alternating current supplied from commercial power supply system.