GB1044452A - Improvements in and relating to measuring transformers - Google Patents

Abstract

1,044,452. Transformers. ALEIDIUS CORNELIS DE VRIES BROEKMAN. Dec. 17, 1963 [Jan. 3, 1963], No. 49781/63. Heading H1T. [Also in Division G1] A polyphase measuring transformer in which the primary A (Fig. 2, not shown) consists of windings connected in polygon (e.g. delta), and has each of the secondary windings B formed of a pair of coils, the two coils constituting each pair being connected in series and being magnetically coupled respectively to two adjacent primary windings, such that the secondary voltages, e R , e s , e T (Fig. 1, not shown) are proportional to the corresponding virtual primary phase voltages OR, OS, OT. The voltage applied to the measuring instruments is then substantially free from third harmonic distortion. The secondary voltages e R , e S , e T may be equal to the corresponding primary phase voltages if the turns ratio of each coil of a secondary pair to its primary is 1: 3. One end of each secondary may be connected to a common point (dotted lines, Fig. 2, not shown) or may be connected to a respective corner of the primary polygon, in which case one of the secondary coils of each pair may form part of the primary, on the autotransformer principle, (B, Fig. 3, not shown). The secondary pairs of coils may have their outer ends connected to the points of the polygon, and have their inner ends connected to a common, effective, neutral point if the turns ratios are all 1: 3 as stated above. The measuring transformer B may be used in conjunction with a conventional measuring transformer A by connection depicted in Fig. 3 (not shown).