The invention relates to a tap changer for the interruption-free switchover between winding taps of a tap-changing transformer. Furthermore, the present invention relates to a novel vacuum interrupter which is particularly suitable for such a tap changer. The tap changer according to the invention is based on the general concept of combining in each case one main contact (V1) and one mechanical switching means (U1), connected in series therewith, of a first load branch and an additional resistive contact (V3) of a second load branch in only a single vacuum interrupter (1) with a common housing (5). The vacuum interrupter (1) according to the invention is furthermore based on the general inventive concept of replacing the functionalities of two required vacuum interrupters in accordance with the prior art and an additional mechanical switching means with a single vacuum interrupter (1) according to the invention by virtue of combining the design of a vacuum interrupter (1) with a plurality of moveable contact systems (I, II, III), which are arranged in separate vacuum interrupter chambers (2, 3, 4) which are sealed with respect to one another.