GB1278068A - Improvements in or relating to transformers - Google Patents

Abstract

1278068 Transformers MIDLAND TRANSFORMER CO Ltd 3 March 1970 [5 Dec 1968] 57709/68 Heading H1T A transformer assembly comprises a main transformer 10 having a primary winding divided into two parts 13, 14 and a secondary winding 15, first and second tapping points 18, 19 on the first and second parts of the primary respectively, first and second tapped auto-transformers 11, 12 having the same number of turns, the first and second tapping points being respectively connected to one end of the first and second auto-transformers and the other ends of said auto-transformers being connected respectively to the inner ends 20, 21 of said first and second parts of the primary, there being an equal number of turns of each part between its inner end and its tapping point; tapping means 27, 28 arranged to make electrical contact with the turns of the auto-transformer windings; means 29 interconnecting the tapping means of the two auto-transformers and means for moving the tapping means in synchronism so as to simultaneously increase or decrease the number of turns of each auto-transformer between said other end thereof and the tapping means. The two auto-transformers are wound on a common core 26. The main transformer may include at least one further tapping point 47 and 49 between the inner end of each part of the primary winding and the first mentioned tapping point, the or each such further tapping point on each part being connected to the winding of the auto-transformer connected at a position 48, 50 such that the proportion of the number of turns of the auto-transformer between said other end thereof and said position to the total number of turns of the auto-transformer is equal to the proportion of the number of turns between said inner end of the part and said further tapping point to the total number of turns between said first mentioned tapping point and the inner end of the part. The means for moving the tapping means is arranged so that the latter will only stop at the ends of the auto-transformer winding or at the positions 48, 50 thereon which are connected to said further tapping points. A variable choice 100 may be interposed between an outer end of one of the primary parts and the supply line L, N and operable to apply the supply voltage gradually to the primary.