AbstractWe have developed large-current-carrying superconducting wires for the application of superconductivity for fast pulsed magnets and ac power devices such as SMES, superconducting rotating machines and transformers. Critical current and ac losses measurements under 50 Hz operation have been performed. Results show that the superconducting wires have ac transport current more than 1000 Arms at 50 Hz with 2 T dc backup magnetic field, and relatively low ac losses. The result also shows that the mechanical rigidity should be carefully concerned togetther with the reduction of the losses in the development of ac superconducting wires.