Patent GB-349148-A (GB)
Title: Improvements in and relating to electric supply systems
IPC: H02J7/18
Filed: 1930-03-01
Abstract: 349,148. Variable - speed generator systems. FOALE, H., 39, Western Road, Wolverton, Buckinghamshire. March 1, 1930, No. 6872. [Class 38 (iv).] A train-lighting or like system having a variablespeed generator and battery and an automatic regulator controlling the field strength of the generator has a resistance in the circuit of the shunt coil of the regulator and control switches therefor arranged so that this shunt coil is only slightly excited when no lamps are on and also up to a predetermined lamp voltage when lamps are on, at which voltage a section of the resistance is shunted and the dynamo output consequently reduced, a further section of the resistance being similarly shunted if the lamp voltage again rises to the said value. The circuit connections are shown in Fig. 1. With a 24-volt lighting circuit the cut-in switch has a shunt coil 10 which closes the main contact 6 at about 26-27 volts. The series coil 8 carries the full dynamo load and the series coil 9 the battery current. When the battery commences to charge a contact 7 is opened to insert a resistance 11 in the lamp circuit. The dynamo voltage is controlled in the main by a shunt coil 17 operating the contacts 14 of a field regulating resistance in sequence, but its action is opposed in proportion to the field strength by a coil 19. The coils 17 and 19 balance each other at the cut-in speed of the dynamo. After cutting in a coil 18 in shunt to a stabilizing resistance 16 in the battery circuit starts the operation of the regulator by assisting the coil 17 in proportion to the rate of charge. The coil 18 also prevents fluctuation of charging current. The normal charging rate may be determined by the choice of a suitable resistance 16. When the battery is charged to 32 volts the charge rate falls, by the action of the regulator, to a small value. When the dynamo slows up the coil 9 hastens cutting-out especially when lamps are on. The lamp circuit is controlled by an electromagnetic switch 29 with " on" and " off " coils and a switch 26 connected to the battery terminal. When the lamp lead 31 is energized a relay coil 24 operates at about 26-27 lamp volts to shunt a section of a resistance 21 in series with the coil 17 by connecting the point 21a to the lamp lead 31. At the same time a relay coil 25 and an electromagnetic switch 4 are energized. The latter inserts a resistance section 12 in the lamp circuit. A switch 13 in series with the coil 4 is operated at a given position of the regulator and a coil 35 in series therewith accentuates the operation of the switch 13. If one lamp voltage rises again to 26-27 volts or a little more the relay 25 operates to connect the lamp lead 31 to the point 21b on the resistance 21 and the dynamo output is still further reduced. These two stages of regulation are dependent upon the existence of a lamp load. A switch 5 operated on closure of the cut-in switch controls a resistance 2 which modifies the operation of the relay 24 when the dynamo is cut out. A coil 37 on the regulator is put into operation by an excess current coil 36 in the dynamo circuit to limit the output of the generator. All the control apparatus is mounted in a common frame 47. The core 40 of the regulator is a piston-fit in a brass tube 41 to constitute a dashpot, the tube being soldered to a core part 42 adjustably screw-threaded in a frame 43. The cores of the remaining electromagnets may be similarly constructed but without airtightness. The core 40 operates a tapered member 51 which disengages the contacts 14 in succession from the short-circuiting contact 52, this being a carbon rod which is reciprocated to maintain clean contact each time the " off " solenoid 27 of the lights switch is operated. A link 53 couples it with a spring-returned member 54 which is moved by a latch-releasing member 56 operated by the core of the solenoid 27. An emergency push 62 may operate this core at need. The lights switch is latched in when operated and released by the member 56 engaging a part 59 attached to the latch.