Thyristor on-load change-over switch

Claim 1

An arrangement in an on-load change-over switch of an on-load tap changer for uninterrupting switch-over of the regulating winding of a transformer, comprising: a regulating stage of the regulating winding; said regulating stage containing a higher winding tap and a lower winding tap; at least two selector contacts; at least two permanent contacts; conductors respectively connecting said at least two selector contacts and said at least two permanent contacts; a common output line; said higher winding tap and said lower winding tap being respectively connected to said common output line through respective ones of said at least two selector contacts and said at least two permanent contacts for conducting load current from a respective one of said higher winding tap and said lower winding tap to said common output line; a first change-over switch; said first change-over switch having a root connection and two switching contacts respectively connected to said higher winding tap and said lower winding tap; said two switching contacts of said first change-over switch being respectively connected to said conductors respectively connecting said at least two selector contacts and said at least two permanent contacts; a load relief circuit interconnecting said root connection of said first change-over switch and said common output line; said first change-over switch switching between said higher winding tap and said lower winding tap such that said load current is briefly passed to said load relief circuit; said load relief circuit containing a second change-over switch and a thyristor circuit; said thyristor circuit being connected in series with said second change-over switch and containing two thyristors in antiparallel connections; said load relief circuit further containing a series connection of a transition resistor and a bridging-over switch; said series connection of said transition resistor and said bridging-over switch being connected to said common output line; said second change-over switch containing two switching contacts; one of said two switching contacts of said second change-over switch being directly connected to said root connection of said first change-over switch; and an other one of said two switching contacts of said second change-over switch being connected to said root connection of said first change-over switch through said transition resistor.