Patent GB-190911400-A (GB)
Title: Improvements in and relating to Electric Systems for Power Transmission.
IPC: H02P7/34
Filed: 1909-05-13
Granted: 1910-03-17
Abstract: 11,400. Allegemeine Elektricitõts- Ges. May 13, 1908, [Convention date]. [Addition to 11,339/09.] Dynamos and motors combined for transmitting power.-In an electric power-transmission system, a motor is connected to a starting-generator, the field of which is influenced by the motor current, as described in the parent Specification, and an auxiliary machine acts in conjunction with the main exciter to neutralize the effect of variation of the generator speed. The working motor 1 and the generator 4 have field coils 3, 6 supplied by the main exciter 7. A regulating-resistance 9 is included in the circuit of the exciter field 8, and, when the exciter 7 and generator 4 are on the same shaft, a governor varies the resistance 9 so that the potential of the machine 7 remains constant. The regulation may also be effected by an electromagnet dependent on the exciter potential. A shunt motor 13 connected across the exciter busbars drives auxiliary machines 11, 12. The field winding 15 of the machine 11 is shunted across a resistence 16 in the main circuit. The armatures 11, 12 are connected in series with the exciter 7 to supply the field 6 of the generator. The machine 12 has a field winding 17 connected to the exciter 7, and a field winding 18 connected in series with the exciter field 8. The controller 10 is put in the circuit between the machines 11, 12 as shown. On the occurrence of a fall in the speed of the exciter 7 or the generator 4, the regulator diminishes the resistance 9, and the current in the field 18 increases. This increases the current in the field coil 6, and raises the electro-motive force of the generator 4. The windings 17, 18 are arranged to neutralize each other under normal conditions, as the machine 12 does not then generate an electro-motive force, but the arrangement may be modified so that the machine normally generates an electro-motive force and may supply the field winding 6 without being connected in series with the exciter 7. The winding 18 may be omitted if the circuit of the winding 17 includes a resistance regulated similarly to the resistance 9. The auxiliary machine 11 may supply a second field winding of the generatoinstead of working in series with the machine 12. The two auxiliary machines 11, 12 may be combined as a single machine with three field windings corresponding to the windings 15, 17, 18. The circuit of the winding 15 then includes a reversing- switch operated from the controller 10. The motor 13, which drives the machine, has a second field winding connected in series with the field 8 of the exciter 7. A secondary battery may be used instead of the exciter 7, and the field of the auxiliary machine is then provided with a resistance varied by a centrifugal governor on the generator shaft. Or, the coil supplied by the battery may be opposed by a coil supplied by a special generator on the shaft of the generator 4. A further modification is shown in Fig. 3. The auxiliary machine 12<11>, in addition to the field coil 15, has a field coil 22 connected across the brushes of the machine 4, and a field coil 21 which takes a current proportional to that in the generator field coil 6. The windings 21, 22 neutralize each other when the generator runs at normal speed. If the speed falls, the winding 21 predominates, and this acts to raise the electro-motive force of the generator 4.