Patent GB-316669-A (GB)
Title: Improvements in or relating to the synchronizing of synchronous dynamo-electric machines
IPC: H02J3/42
Filed: 1929-07-22
Abstract: 316,669. Siemens - Schuckertwerke Akt.-Ges. Aug. 2, 1928, [Convention date]. Synchronizing dynamoelectric machines. - In synchronizing a synchronous dynamo-electric machine 2 with supply mains 1 it is connected in parallel therewith through choking coils 3 and with a weakened excitation by means which, proportionately to the increase of frequency difference between mains and machine potentials increases the phase displacement between the instant of phase agreement and that of initiation of the impulse for closing the paralleling switch so that the time interval between these instants remains the same. The choking coils may be automatically short - circuited as described in Specification 299,015. The exciter 22 may have an opposing field winding which is reversed on synchronizing to assist the normal excitation. The arrangement according to Fig. 1 comprises a synchronoscope 7 energized from the mains 1 and, through interlock contacts 9, from the machine 2. The synchronoscope energizes a time delayed relay 12 which, jointly with another contact on the synchronoscope energizes a relay 13 to initiate the closing impulse for the coil 11 on the paralleling switch 4. The exciter switch 23 is energized by an auxiliary contact on the switch 4 when it closes, and the short circuiting of the choking coils 3 is subsequently effected by a voltage relay 16 subject to a time delay relay 18 and an exciter current relay 17. A master control switch 24 is not closed until the machine is up to speed since an exciter voltage relay 21 controls a master switch 24. According to the invention, in one form, the synchronoscope has a rotating arm 645, Fig. 4, co-operating with contacts 648, 649 controlling the relays 12, 13 respectively. These contacts are carried by a disc 643 which is centralized by springs 654, 655 but displaced proportionately to the frequency difference between mains and machine potentials by a driving magnet 653 connected between the two sources. The phase advancement is obtained according to Fig. 2 by two synchronous generators 26, 27 driven respectively in synchronism with the mains and machine potentials by motors 28, 29. A resilient coupling is interposed in the drive for machine 27 and a phase displacement of the voltage of the machine 27 is produced by an asynchronous motor 31, excited from the mains potential, the rotor of which is coupled with the machine 27. A minimum potential relay 25 in series with machines 26, 27 controls the circuit of coil 11, Fig. 1. Fig. 3 shows a further modification. To prevent closure of the switch 4, Fig. 1, with too great a frequency difference set time delay relays 43, 44 are in turn energized during alternate half cycles by a relay 41. A minimum potential relay 55 closes its contacts only when not energized, that is when the moving contact of relay 41 is in mid-position which occurs when voltages derived from the mains and machine potentials are in phase; a maximum potential relay 42 closes its contacts when the mains and machine potentials are approximately in phase. The potential derived from the mains is displaced in proportion to the frequency difference between it and the machine potential for the operation of the relays 41 and 55 by an auto-transformer 46, resistance. 45, and capacity-inductance tappings controlled by a switch arm 47. Direct-current machines 48, 49 in series energize a coil controlling this switch arm proportionately, to the frequency difference so that the potential between points 64, 66 varies in phase over approximately 180 degrees in accordance with the frequency difference.