Patent GB-261844-A (GB)
Title: Improved method for automatically controlling electrical apparatus in accordance with the circuit conditions
IPC: H02J3/38
Filed: 1925-08-27
Abstract: 261,844. General Electric Co., Ltd., and Ang-old, A. E. Aug. 27, 1925. Systems depending on the use of two or more machines or transformers. - A machine of a group of generators 18 - - 21, Fig. 2, rotary converters, or transformers, is started up or shut down, according to the condition of a circuit 22 fed by the machines, by one of two relays 31, 32 which operate after a period of time which is longer if abnormal conditions in the circuit 22 occur intermittently rather than continuously, and which operate to use the machine in rotation. Each of the relays comprises a disc 9, Fig. 1, which is driven in the direction of the arrow when the winding 11 of a shaded pole core is energized, and is driven in the reverse direction when the winding 11 is not energized by another winding 14, constantly energized but producing a smaller torque. A contact 1 is gear driven from the disc 9 and co-operates with groups of fixed contacts 2 - - 5. If the winding 11 is energized, the contact 1 moves towards the contact 2, but if it is de-energized before the contacts 1, 2 engage, the contact returns as a slower rate to the position shown, where it is prevented from further reverse rotation by a pawl 17 and ratchet 16. Thus approach of contacts 1, 2 is slower if energization of winding 11 is intermittent rather than continuous. Should the forward motion be sufficient for contacts 1, 2 to engage, then a maintaining circuit is completed for the winding 11 to cause the contact 1 to sweep over the contacts 2 until it reaches the next " off " position where the pawl 17 engages the next ratchet tooth, whereupon the relay is in a similar state in respect to contacts 3 as it originally was in respect to contacts 2. The contact 1 may be resiliently connected to its spindle so as to give a sharp break with the fixed contacts, and the winding 14 may only be energized when the winding 11 is deenergized. As applied to the system shown in Fig. 2, the relay 31 has its winding 14 constantly energized from an auxiliary alternating current supply 33. Upon the occurrence of low voltage in the circuit 22 as determined by a relay 36, or of an overload on one or more of the machines 18 - - 21 as determined by overload relays 23 - - 26, the circuit of the winding 11 is completed, the abnormal condition persists continuously or sufficiently intermittently, the contact 1 engages the contacts 2 completing a maintaining circuit for the winding, and also energizing a lead 37 connected to apparatus for starting-up generator 18. If the abnormal condition continues, owing to the generator 18 failing to start or being incapable of dealing with the increased load causing the abnormal condition, the relay 31 continues its motion until contacts 1, 3 engage, whereupon generator 19 is started up, the action continuing until sufficient generators are in action. Upon the load on the circuit 22 decreasing sufficiently, one or more of the underload relays 27 - - 30 complete the circuit of the winding 11 of the second relay 32 causing this in a similar manner to energize a lead 43 connected to apparatus for shutting-down generator 18, and if the underload conditions still continue, other generators are also shut down. When next it is necessary to start-up a generator, the relay 31 will engage the contacts immediately following those last engaged and thus each of the machines 18 - - 21 will have approximately equal usage over a long period of time. The relays 23 - - 30 and 36 may break the circuit of the windings 14 when they complete the circuit of the windings 11.