Patent GB-417381-A (GB)
Title: Improvements relating to dynamo electric generating apparatus
IPC: H02J7/22
Filed: 1933-03-03
Abstract: 417,381. Variable speed generator systems ; charging and discharging batteries ; exciting generators. PESTARINI, G. M., 4, Tapton House Road, Sheffield. March 3, 1933, No. 6579. [Classes 35 and 38 (iv)]. A generator operating in parallel with a battery is excited by a " metadyne " on the same shaft; the voltage of the generator is normally proportional to the exciting voltage of the metadyne and means are provided for disturbing this proportionality when there is danger of the battery discharging through the apparatus or being overcharged; the proportion may also be somewhat varied by designing the metadyne and generator so as not to be saturated at the same speed. In the arrangement shown in Fig. 4 the battery 8 is connected to the primary brushes a, c of the metadyne 3 through a resistance 17 so that when the apparatus starts the metadyne is feebly excited and excites the generator 1. When the generator current reaches a certain valve a coil 15 closes a switch 14 which short-circuits the resistances 17 and a switch 20, which, after a delay produced by a dash-pot 21, closes a switch 18 putting the battery 8 and loads 6, 7 in parallel in the circuit of the generator 1. If the speed falls so far that the generator can no longer charge the battery, the latter discharges through a coil 16 and opens the switches 14, 20 and 18. To prevent overcharging a resistance 22 is interposed between the generator 1 and the battery and is normally short-circuited by a switch 23, which is opened when the voltage reaches a certain valve. This resistance may be replaced by a winding on the metadyne which decreases the secondary current therein and is controlled by a switch in the same way as the resistance 23. In the arrangement shown in Fig. 5 the voltage of the metadyne 3 is regulated by a winding 27 in line with the primary brushes a, c, the current in the winding 27 being controlled by a Tirrill regulator 28 operated by the voltage of the generator 1, a resistance 29 being inserted in the primary circuit of the metadyne. The regulator 28 may be replaced by a carbon pile resistance in parallel with the exciting winding 2 of the generator 1. Fig. 5 also shows a resistance 30 between the battery 31 and the lamps 32 which is in circuit while the battery is being charged but is short-circuited by a switch 33 when the battery is discharging through the lamps. Permanent magnets 41 provide a field for the metadyne when it and the generator are running slowly, thus replacing the switching arrangement shown in Fig. 6. Instead of or in addition to, the magnets 41, magnets 42 may be placed in the main brush axis of the generator 1, which then has an additional winding 43 connected across brushes 44, 45. Instead of exciting the metadyne from the battery it may be excited by the arrangement shown in Fig. 7, consisting of a motor-generator, the motor 38 being unsaturated, shunt excited and fed by the generator 1, while the generator 39 is saturated and has a field winding excited from the same circuit as the motor 38. Specification 404,739, [Group XXXVII], is referred to.