SHORT-CIRCUIT TESTS ON CURRENT-LIMITING FUSES - MODELING OF THE TEST CIRCUIT

In the standard procedures for high-power short-circuit testing of cur rent-limiting fuses, the test circuit is conventionally characterised by the RMS test voltage, prospective current, frequency, closing angle , and power factor. From these parameters a constant RL equivalent cir cuit can be derived, which has been widely used in the modelling of fu se-breaking transients, but recent studies have shown that this circui t model is inadequate. The frequency dependence of R and L has been in vestigated by fast-Fourier-transform analysis of fuse-breaking test tr ansients obtained in a high-power short-circuit test laboratory, and t he results show that, while L decreases slightly, R increases greatly with frequency. The nominal-power-factor value provides only a measure of the DC resistance of the circuit. The frequency dependence of R mu st be taken into account for accurate modelling of the operation of li miting fuses.