Overload protection for transformer stepping switch - includes spark gap and fuse assembly in series with load dependent resistance between tappings

摘要

The stepping switch for a transformer for transferring the load between connections with a voltage dependent resistance (SAW) between them includes a changeover resistance (R1,R2) in series with the two connections (A1,A2). Each changeover switch has its own oil filled vessel, and the two parallel paths incorporate sets of relay contacts (D1,D2,H1,H2) and selector contacts (W1,W2). In series with the voltage dependent resistance is a fuse (S) with a pair of contacts in parallel with it, forming a spark gap (F). The fuse and contacts form a single unit, and when the fuse melts, the arc formed is carried by the contacts.