Patent GB-346265-A (GB)
Title: Improvements in transformers for three-phase to two-phase conversion
IPC: H01F30/14
Filed: 1929-11-04
Abstract: 346,265. Phase changing systems ; transformers. TAYLOR, A. M., Inkford House, Wythall, near Birmingham. Nov. 4, 1929, No. 33461/29, 34436/29, 38420/29, 3558/30, 7594/30 and 14092/30. [Classes 38 (ii) and 38 (iv).] A transformer system for converting 3-phase current into 4-phase current or vice versa comprises on the 3-phase side a group of eight windings EF, GH, SM, JK, NV, VX, YW, WQ and a group of four windings CD, LP, RT, AB having @ times as many turns as the first group and being arranged on cores in which the flux is 90‹ out of phase with that in the cores carrying the first group. The windings indicated by broken lines are wound reversely with respect to those shown in full lines ; the windings being connected in series in pairs and to the neutral point o and the 3-phase system 1, 2, 3. On the 4-phase side, windings T<2>, T<4> are associated with the cores carrying the first group of the 3-phase windings, and windings T<1>, T<3> are associated with the cores carrying the second group of the 3-phase windings, a neutral point o<1> being provided so that connections may be made to a five-wire 4-phase system. As shown in Fig. 4, the 4-phase windings mav be subdivided and so arranged in pairs on the cores that, in the event of a fault developing on the transmission system feeding the transformer and causing one half of the 4-phase system (e.g. the windings connected to phases T<2>, T3) to be deenergized, the transformer (which is then receiving energy through phases T<1>, T<4> only) may by an appropriate setting of switches S<1> .. S<4> be caused to feed back to the fault on phases T<2>, T<3> due to the fact that the windings fed by the phases T<1>, T4 are inductively coupled to windings connected to the phases T<2>, T<3>. The two windings on each core are so wound and connected that the potential difference between two adjacent points on the two windings at any point along the core is the same and equal to halve the potential difference between points a and c for example. The 3-phase windings are also subdivided into two similar halves so that the transformer system comprises two pairs of cores, each pair carrying a set of 3-phase and a set of 2-phase windings, one set of the latter comprising phases T<1>, T<2>, and the other set comprising phases T<3>, T<4>, Thus, in the event of a breakdown in the windings associated with either pair of cores, a spare half unit comprising a set of 3-phase and a set of 2-phase windings may be substituted for the faulty half of the working transformer. In order that such a spare half unit may be substituted for either half of the working transformer (i.e. the half comprising phases T<1>, T2, or the half comprising phases T<3>, T<4>) the spare must be provided with a reversing switch on either the 3-phase or the 2-phase side. Fig. 6 shows on the right a spare half unit with a reversing switch RS for the 3-phase windings T<5>, T<6> so that the 2-phase windings a, n, and b, n may be connected to phases H<1>, H<2> normally fed by windings T<1>, T<2> of the working unit, or to phases H<3>, H4 normally fed by windings T3, T4 of the working unit. Fig. 7 shows the alternative form of spare half unit in which a reversing switch RS is associated with the 2-phase windings T<5>, T<6> in order that they may be connected to phases H<1>, H<2> . or to phases H<3>, H<4> which are fed normally by windings on the working unit T<1>, T2 and T3, T4. The reversing switches are preferably oil-immersed and may be situated within the transformer casing.