Measurements of Ag/Bi(2223) superconducting tapes have been performed between dc and 30 KHz for under and upper critical currents, up to 2 or 3 times i(c). A fast power amplifier (100A 30KHz) has been specially built for pulsing such currents in the samples. Measurements in this type of samples show some ac losses. Modeling based on the dc non linearity, triangle and sine measurements is made in such a way that the behavior of superconducting devices using this type of tapes can be predicted, for any currents in frequency ranges up to 30 KHz and intensity up to 3 times i(c). We observe an excellent superconductivity recovery of these samples, and our simple equivalent circuit model offers a good prediction of the sample behaviour.