Development of a quick response persistent current switch [for SMES]

The paper describes the test results of a 100 A persistent current switch and the design of a 1.5 kA persistent current switch for use in SMES applications. These switches are of transformer-type, based on the principle of a current transformer. In order to increase resistance in the switch-off mode, bifiliar windings with a negligible small inductance are inserted into the secondary circuit of the transformer. Tests of 100 A persistent current switches have been performed with satisfactory results such as switch-off resistance of 50 /spl Omega/, switch-off time delay of 20 ms and operational current of 100 A. A 1.5 kA persistent current switch has been also designed to have a response time shorter than 100 ms and a switch-off resistance larger than 100 /spl Omega/.