GB459227A - Improvements in regulating switches for electric transformers - Google Patents

Abstract

459,227. Transformers. JANSEN, B., 7, Brunnleite, Regensburg, Germany. April 23, 1935, No. 12228. Convention date, April 20, 1934. [Class 38 (ii)] [See also Group XXXVII] An on-load tap-changing arrangement for a transformer comprises a series of fixed contacts connected to the tappings and two groups of contacts which are moved alternately during each change-over operation, the groups having contacts connected directly and indirectly with a common current lead, the indirect connection being through resistances which during changeover form a voltage-divider connection between the current lead on the tappings being changed. Fig. 1 shows one arrangement in which the tappings are connected to contacts 1-6 which engage with the main and auxiliary contact arms I, II. The auxiliary contact arm has two contacts h1, h2 which are connected to the main contact H and the main circuit A through resistances W1, W2. To effect on-load tap change, the auxiliary arm II is first moved so that the contacts h1, h2 engage the contacts 1, 2 ; the arm I is then moved from contact 1 to contact 2 ; finally the arm II is moved so that the contacts h1, h2 are disengaged and lie on either side of contact 2. In a modification of this, for a transformer having a winding with a break in it and tappings arranged symmetrically about the break ; alternate contacts are connected to tappings on opposite sides of the break; the main contact arm has two contacts so that two adjacent contacts are bridged and the auxiliary arm has three contacts, the two outer being connected to the centre by resistances. In an arrangement for a three-phase star connected transformer with the tappings arranged at the star point, adjacent contacts are connected to tappings on different phase windings, the main contact arm having three contacts so as to engage three adjacent contacts and thus form a star point to the three phase-windings, while the auxiliary arm has four contacts, the outer contacts being resistance connected. With this arrangement one tap-changing operation shifts the tapping on one phase winding only, the next operation shifting the tap on the next winding and so on. Fig. 3 shows a further arrangement of contacts and operating mechanism. Here the contacts are arranged in two semicircular groups, diagonally opposite contacts being connected to the same tappings The main moving contacts H and auxiliary contacts h1, h2 are mounted to be moved by an eccentric E. Rotation of the eccentric engages contacts h1, h2 with contact studs 3, 4 and then disengages contacts H from contact stud 4. Further rotation moves contacts H and engage. them with contact stud 3, finally disengaging contacts h1, h2 from contact studs 3, 4 as shown in position 3. Fig. 4 shows a further arrangement in which the two contact arms I, II are slotted to engage pins A, B on a single camoperated disc F. Rotation of the cam causes substantially alternate operation of the arms I, II. In this arrangement for a tapping connection in which the tappings are arranged symmetrically about a break in the windings, each arm comprises a main contact H1 and an auxiliary resistance connected contact h1. When in the main position, the resistance W1 is short-circuited by the main contact H2 and the resistance W2 by the contact H1. In the intermediate transfer position, the contacts 2 and 4 are each connected to the contact 3 through the resistance. In a modification of this, for a three-phase system, the main contacts H1, H2 are lengthened to bridge two contacts. The Specification as open to inspection under Sect. 91 comprises also the arrangement shown in Fig. 3 (Cancelled) for a three-phase star connected transformer in which the contact groups I, II are moved by cam-operated toothed discs R1, R2. This subject-matter does not appear in the Specification as accepted.