Patent GB-167242-A (GB)
Title: Improvements relating to dynamo electric machines adapted for synchronous working
IPC: H02K19/32
Filed: 1920-04-29
Abstract: 167,242. Hunt, L. J., and Sandycroft, Ltd. April 29, 1920. Dynamos, regulating; motors, controlling; exciting; windings.-Relates to a dynamo-electric machine having stator windings adapted to operate with alternating current and to produce fields of two different pole-numbers, and having a rotor winding also adapted to provide fields of two different pole-numbers, the rotor winding being excited by continuous current at one or more speeds of operation. The rotor winding is of a type having six terminals and is arranged so that when continuous current is supplied to any pair of the terminals, the remaining terminals can be interconnected so as to provide local circuit paths through the coils for damping purposes and for maintaining synchronism. The rotor winding shown in Fig. 1 is wound to produce two or four poles and to give a cascade speed corresponding to six poles. The four-pole excitation is obtained by connecting the source of continuous current o to the slip-rings 1, 7. The damping- circuits are obtained by interconnecting the sliprings 3, 5, 9, 11 either in the manner shown in Fig. 1 or in the manner shown in Fig. 5. For the two-pole excitation, one terminal of the continuous-current source is connected to the sliprings 1, 7 and the other terminal to the sliprings 3, 5, 9, 11. The stator may be provided with two windings wound for four poles and two poles respectively, the two-pole winding being excited by continuous current when the machine is to operate as a synchronous six-pole (cascade) motor. If the machine is required to operate at the speeds corresponding to the two basic polenumbers only, the stator winding is preferably arranged so that it can be connected up as parallel-mesh winding for the two-pole speed as shown in Fig. 12, and as a parallel-star winding for the four-pole speed as shown in Fig. 11. In Fig. 13 are shown the circuits and controllers v, w for a motor adapted to operate at the three synchronous speeds corresponding to six poles, four poles, and two poles. Resistances 34, 35, 36, 37 are used for starting purposes as described in Specification 124,018. The motor is started a.; an induction motor with the opposite terminals of the rotor winding connected together through the resistances 34, 35, 36, 37, and run up to the synchronous speed by shifting the brushes 16, 13, 17, 14, 18, 15 so as gradually to cut out the, resistances. For the six-pole synchronous speed, the continuous-current generator is connected across the stator two-pole winding a, b, c and the slip-rings 3. 7, 11 are short-circuited, the four-pole stator winding d, e, f being supplied with alternating current. For four-pole synchronous operation the connections of the rotor winding are those shown in Fig. 5, the continuous-current generator o being connected to the slip-rings 1, 7 through the contacts k, l. For two-pole synchronous operation the terminal h of the generator o is connected to the slip-rings 1, 7 and the terminal g to the slip-rings 3, 5, 9, 11 through the connections n, m and brushes 16, 13, 17, 14. Specifications 8403/04, 16170/09, 9261/13, 24837/14, 24838/14, 15113/15, and 124,018 are referred to.