Patent GB-258618-A (GB)
Title: Improvements in or relating to electrical pole changing systems
IPC: H02K17/14
Filed: 1926-09-20
Abstract: 258,618. Weinert, H. Sept. 20, 1926. Alternating-current motors; motor, control. ling.-A 6-n-pole 3-phase motor winding having 9n winding elements giving 6n or 2n poles is characterized by each phase consisting of (i) two groups of adjacent elements separated from each other by 6 and (ii) those single elements which lie between these groups and are displaced from each group by 8#/3 and are connected with reversed connections to give 2n poles. The angle 2 # corresponds to 360 electrical degrees in the 6n-pole connection. Known methods may also be provided for giving pole ratios of 6: 4 and 6 : 3, and for all pole numbers, the same winding elements are in operative use. Fig. 1 shows the winding elements 1 - - 18 for a 3-phase 12-pole machine (n=2) which for 12 poles are normally grouped in delta, as in Fig. 2. For 4-poles, the elements are grouped as in Fig. 3, so that phase I, for instance, comprises the two groups 1, 18 and 9, 10, separated by 6 # together with the intermediate elements 5, 14 which are separated from each of the two groups by 8#. The elements 5 and 4, 8 and 17 and 2 and 11 are reversed end for end, as shown by the minus signs. The elements in a phase or of the several phases may be grouped together in series or parallel, as shown, for instance, in Fig. 5 in which each phase of the arrangement of Fig. 3 is divided into two parts and these parts are in paralleled-star grouping. Mixed star-delta connection may be used, as in Fig. 7, which shows a 4-pole grouping, the reversed elements -2, -11, -5, -4, -8, -17 forming the delta and each star arm containing elements of two different phases. Another star-delta grouping is also shown in which each of the arms of the star consists of two single winding elements, such as 5, 14, in series and reversed so that their " beginning '' ends are directed towards an apex of the delta. Fig. 10 shows a series-parallel grouping for eliminating the disadvantage in plain stardelta groups of star currents 3 times as great as the delta currents. The star arms consist of paralleled groups of two elements in different phases. The Specification, as open to inspection under Sect. 91 (3) (a), comprises also the following :- The grouping of Fig. 3 when rearranged without reversals, as shown in Fig. 3 (Cancelled) gives 8 poles. An 8-pole winding may also be obtained from the grouping of Fig. 7 by connecting the star-delta as in Fig. 6 (Cancelled). An alternative 8-pole star-delta connection is shown in Fig. 8 (Cancelled), in which each side of the triangle contains four elements in series, for instance the elements 9, 18 and 7, 16 of phases I and III respectively. The open terminals of elements 2, 14, 17 may be joined together, in which case the phase terminals are transferred to the apices of the triangle. The inequality between the delta and star-arm currents in such groupings and the resulting heating inequality may be reduced by winding with elements of different cross-sections. A method is also described for bringing out thirteen terminals from the eighteen elements for connection to a controller to convert from 12 to 8 poles and fifteen terminals for conversion from 12 to 8 or 4 poles. It is stated also that a delta connection of the eighteen elements may be changed from 12 to 6 poles by connecting the apices of the triangle together and using the centre points of the triangle sides as phase terminals. This subject-matter does not appear in the Specification as accepted.