ON-LOAD TAP-CHANGING ARRANGEMENT FOR STAR-POINT CONNECTION TO TAPPED TRANSFORMERS OR CHOKES

摘要

1,236,505. Transformers. SIEMENS A.G. 20 Oct., 1969 [18 Oct., 1968], No. 51428/69. Heading H1T. In a tap changing arrangement for the star point of a polyphase transformer, two polyphase rectifier bridges 40, 50 are connected to tap selector arms 2, 3 respectively, each bridge having a respective controlled rectifier 60, 70 or mechanical switch. Fig. 1 (not shown) in its D.C. arm. The negative poles of the controlled rectifiers are connected by a capacitor 110 and the positive poles by a capacitor 150 such that when tap selector arm 3 is connected to a free tap, both capacitors charge to the differential tap voltage. When controlled rectifier 70 is then fired these capacitors cause twice the differential tap voltage to appear across the rectifier to be switched off thus ensuring its immediate switching off. Inductors 900, 800 help the smooth commutation process. By controlling the pulse inputs to the rectifiers the tap changeover can be made a gradual process. In Fig. 1 (not shown) interlinked mechanical switches are used instead of the controlled rectifiers, the discharging capacitors in this case suppressing the arc which develops at the " opening " switch.