GB946452A - Improvements in and relating to tap-changing circuits for transformers - Google Patents

Abstract

946,452. Transformers. SOC. GENERALE DE CONSTRUCTIONS ELECTRIQUES ET MECANIQUES (ASTHOM). June 8, 1960 [July 28, 1959], No. 20130/60. Heading H1T. A tap changing system comprises a main transformer with its secondary 1 tapped at equal intervals 7, 8, 9 (Fig. 1), an auxiliary transformer 12 having the load connected to the mid-point 19 of its secondary 11, means 26 for reversibly connecting the primary 21 of the auxiliary transformer between output terminal 6 of the main transformer secondary and the tappings thereon through contactors 30, 29, 32, 31 and an impedance 33 which is cut in and out during tap changing, the two ends of the auxiliary secondary 11 being connected through main contactors 16, 15, 18, 17, 20 to the ends and the tappings of the main secondary 1. Operation begins with main contactor 16 closed and both ends of auxiliary primary 21 connected to terminal 6. Primary 21 is then connected a step at a time across main secondary 1 until tapping 9 is reached, impedance 33 being cut in and out at each step. At that point main contactor 15 closes and 16 opens and the connection of auxiliary primary 21 across the main secondary is then reduced step by step until both ends of primary 21 are connected to terminal 6. At this point reversing switch 26 is operated to reverse the connections of auxiliary primary 21 which is then connected step by step across the main secondary 1 as before and so on. Two impedances may be used instead of one (Fig. 3, not shown) and a pair of tapping contactors may be provided for each tapping point (Fig. 4, not shown).