ABSTRACT
For higher voltages (say Uc in the range 100-1000 V) the design of the switch again must ensure the development of a high UA > Uc. This usually cannot be achieved by just opening the contacts further. In order to achieve a higher UA the arc must be cooled or split into a number of series arcs by driving it into deion plates or into narrow insulating slots (see Chap. 12). The designer has to be careful, however, not to increase UA too rapidly, because it is still possible for the arc to restrike in the residual hot gas remaining between the contacts. For circuit voltages greater than - 1000 V other means have to be used to drive the current in the switch to zero. These are beyond the scope of this book, but examples of successful very high-voltage d.c. switches are given in references (4,5).
