Patent GB-381577-A (GB)
Title: Improvements in or relating to the synchronisation of alternating current electricalapparatus
IPC: H02J3/42
Filed: 1931-04-09
Abstract: 381,577. Synchronizing dynamo-electric machines ; electromagnetic switches. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, WILLOUGHBY, R., Riding House, Stocksfield-on- Tyne, and GIBSON, J. W., of General Electric Co., Witton, Birmingham. April 9, 1931, No. 10495. [Claas 38: (iv).] In an automatic synchronizing arrangement, an element is driven at a speed dependent on the difference of frequency between the busbars and the incoming machine and in a direction dependent on whichever frequency is the greater for operating switching means to effect frequency regulation and closure of main switch when synchronism is attained. To start synchronizing operations for an alternator 50, Fig. 3, a plug is inserted in the socket 75 which connects the contacts 76 and 77, and the hand switch 64 is closed. The operating coil 63 is energized from the control bus wires 123, 124 and closes the switch 61, a maintaining circuit being completed by the auxiliary contacts 62. Closure of switch 61 connects the stator 2 of a 3-phase motor 1 to the main bus-bars 52. The coils 102 of a relay 105 are energized to close the contacts 103 and complete the circuit of coil 70 which closes switch 69 and connects the incoming supply to the rotor of the motor 1. The motor therefore runs at a speed which is dependent on the difference between the frequencies of the bus-bars and the incoming machine 50, and in a direction dependent on whichever frequency is greater. The motor drives a disc 8, Fig. 1, of insulating material on which is mounted a contact having a narrow segment 7 on the circumference and a triangular segment 14, Fig. 3, on the face. Co-operating with this contact are contacts 9 and 10. Contact 10 may be adjusted radially to vary the arc of contact with 14 whilst 9 is mounted on a magnet 32 which can be deflected by a disc 26 rotated at a speed proportional to that of the motor. Since the deflection is dependent on the speed the contacts 9 and 10 will not be connected by the contact 7, 14 until synchronism is practically attained and the phase relationship is correct. Mounted on the rocking magnet 32 is also a contact 15 which, according to the direction of its deflection, makes contact with one of two contacts 16, 17 mounted on levers 46, 45 which are rocked by means of a cam 49 driven from the motor 1. If the frequency of the incoming machine is lower than that of the mains the arm 15 makes intermittent contact with 16 and periodically closes the circuit of a relay R92 which closes a switch R91 in the motor 78, 79 circuit to alter the governor setting of the prime-mover. Similarly contact with 17 closes the circuit, of a relay L88 to alter the governor setting and obtain reduction in speed. When the voltages are equal the relay 102 is de-energized and the armature will bridge the contacts 104. When synchronism is sufficiently approached, the contact 7, 14 will bridge contacts 9, 10 to complete the circuit of a relay 116 which closes through a relay 57 the main switch 54. Opening of contacts 55, 56 disconnects synchronizing apparatus. If the machine reaches synchronism but out of phase an inching relay 101 periodically closes the circuit of relay R92 to alter slightly the frequency of the incoming machine so that the contact 7, 14 would move round to bridge the contacts 9, 10 to effect closure of main switch. A modified circuit of the inching relay is described.