Abstract: A multiphase under load transfer switch of the Jansen-type for tapped regulating transformers. The main contacts and the switch-over contacts of the transfer switch are formed by vacuum switches. The vacuum switches are operated by a common drive mechanism for all of the vacuum switches of all three phases of the transfer switch. The required sequence of the operation of the vacuum switches is achieved by interposition of lost motion connection means between said common drive mechanism and pairs of aligned operating rods for pairs of superimposed vacuum switches. A special common drive mechanism for said pairs of aligned operating rods for operating pairs of superimposed vacuum switches includes a squirrel-cage-like system of helical compression springs which are loaded by pivotable cam means and operate, when subsequently expanding, said pairs of vacuum-switch-operating rods by the intermediary lost motion connection timing means.

Abstract: A transfer switch for load-tap changers of the Jansen-type is provided with a non-linear surge voltage protective resistor forming a shunt across two taps of a tapped transformer winding and arranged in such a way that a breakdown of the resistor does not result in a short-circuit across the section of the tapped winding situated between the two taps.