Patent GB-426048-A (GB)
Title: Improvements in electric ship propulsion systems
IPC: H02P9/04
Filed: 1933-07-27
Abstract: 426,048. Systems for transmitting mechanical power. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, COATES, H. J., and EMMS, S. A. G., c/o General Electric Co., Witton, Birmingham. July 27, 1933, No. 21127. [Class 38 (iv)] In an electric ship propulsion system in which port and starboard D.C. motors are respectively supplied with power from different generators, both motors are automatically supplied from one source of power in the event of the other failing. The fields of both the motors and generators are energized from an independent source, and the various relays for effecting the changes are responsive to reduced generator speed, or to excessing current in the generator or motor field circuits or in the armature circuits. The starboard engine 9 drives a generator armature 7 which is connected in series with the starboard motor armature 1 by a make-beforebreak switch 13. On the port side the engine 12, generator armature 10 and motor armature 3 are similarly connected, and the leads 23, 33 from the starboard and port armatures are connected by the common conductor 24 to the leads 27, 34 from the generator armatures. The conductor 24 is normally closed by the main contacts 25 of the common connection switch having auxiliary contacts of which 47, 48, 49, 50, 239 are normally closed, while 45, 46, are normally open. The conductor 24 is also earthed through a resistance 38 and the contacts 40 of a circuit breaker. Ammeters 41, 42 and overcurrent relay coils 43, 44 are connected across resistance 28, 35 in the armature circuits. The starboard generator and motor shunt fields 8, 2 and the corresponding fields 11, 4 on the port side are connected across the independent current supply leads 52, 53. All the starboard relay and other components now to be described have their counterparts on the port side. Speed is regulated by inserting resistances 87 in the generator field 8, these resistances being inserted when going ahead or astern by the arm 89 of the starboard controller. The propeller is reversed by reversing the motor field 2, this being effected by the arm 106 of the controller acting through relays. When the controller is in neutral, the motor field ahead contactor 55 and the motor field astern contactor 56 are in the positions shown, each having then three contacts closed and five open. The fields 2, 8 are then short circuited. When the controller is moved into the forward position, the arm 106 completes a circuit from the main lead 52, through ring 107, line 111, contact 63, operating coil 64, contact 81, line 209, contacts 73 and line 210 to the main lead 53. The open contacts of the ahead contactor 55 are thereby closed and the closed contacts opened. The completion of this circuit through the contact 81 of the reverse contactor 56 ensures that the ahead and reverse contactors cannot be operated at the same time. The closing of the main contacts 57, 58 completes a circuit between the main leads 52, 53 through the motor field 2. The main contacts 57, 58 when open, close the generator circuit through a discharge resistance 152. The opening of the contact 63 puts an economy resistance 211 in series with the operating coil 64, allowing only sufficient current to flow to maintain the position of the contactor 55. Contact 61 completes a circuit from ring 108 of the controller through the operating coil 101 of the generated field contactor, by way of the contact 119 in the interlock contactor, thus closing the contact 99 and completing the circuit through the generator field. At the same time the economy resistance 102 is put in series with the coil 101, and current may then also be supplied through contact 60 of the contactor 55. When the generator voltage has built up sufficiently, operating coil 115 of the interlock contactor, which is connected across the armature, is energized, thus opening contact 119 and closing contact 118. This gives an alternative supply to the operating coil 64 of the contactor 55 thus preventing its return to the zero position when the controller arm 106 is returned to its neutral position until the current in the motor armature 1 is sufficiently reduced. When running astern, the controller arm 106 makes contact with the rings 84, 110, thereby operating the motor field astern contactor 56 which sends current in the reverse direction through the motor field 2. Should the starboard engine 9 fail, the underspeed contacts 228 close, and a circuit is completed through the trip coil 96, thus opening contacts 94 and closing contacts 95. The same effect is produced by an excess current in the generator field 8 acting through the coil 93, or by throwing over the switch 13 connecting the armature circuits, and thus closing the contacts 17. The underspeed generator control 228 may be replaced by low voltage relays operated when speed decreases, by magneto generators driven by the engine 9. The opening of the contact 94 de-energizes the coil 101 of the generator field contactor, disconnecting the generator field 8 from the mains 52, 53 and short circuiting it through the discharge resistance 238. The closing of the contacts 95 completes a circuit between the mains 52, 53 through an operating coil 51 of the common connection switch thus opening contacts 25 in the common connection 24, closing contacts 45, 46 and opening contacts 47, 48, 49, 50, 239. The opening of the contacts 25 puts the starboard and port motor armatures 1, 3, the port generator armature 10 and the starboard dead armature 7 in series so that both motors are driven by the port generator 12. The dead armature 7 may be cut out by the switch 13. The opening of the contacts 49, 50, inserts resistances 67, 140 in the starboard and port armature field circuits, these resistances having been previously short circuited by the contacts. In this way the field strengths are reduced to suit the reduced voltage available for each of the motor armatures. Either motor may be reversed by its controller independently of the other, but the speed for both depends upon the position of the port controller only. The motor field overload contactor 73 is opened by the winding 72 when an excess current flows through the motor field 2 or when the relay coil 74 is energized due to closing of the contacts 127 of the overcurrent relay, the coil of which forms a shunt from the resistance 28 in the circuits of the starboard armature. The opening of the contacts 73 causes the deenergization of the coil 64 of the motor field ahead contactor 55 or alternatively the coil of the astern contactor 56 and also the coil 101 of the generator field contactor so that both the starboard generator and motor are put out of action leaving the port side in operation. Reference is made to a modification in which reversal of the motor is effected by reversal of the generator field. The system may be applied when the port and starboard power plants each include more than one motor or generator associated as described in Specification 342,448. Specification 416,974 also is referred to in the Provisional Specification.