Patent GB-1116055-A (GB)
Title: Improvements in or relating to alternating-current electric generator with regulation independent of temperature
IPC: B60L50/12
Filed: 1966-06-06
Abstract: 1,116,055. Alternators; driving arrangements. COMPAGNIE ELECTRO - MECANIQUE. 6 June, 1966 [8 June, 1965; 24 Jan., 1966], No. 25083/66. Heading H2A. An A.C. generator plant for railway traction of which the main alternator 1, Fig. 1, driven by a Diesel engine, has its rotary field winding 2 fed, through a shaft-mounted rectifying bridge 4, by an auxiliary excitation alternator 3, 6 having its armature 3 mounted on the main alternator shaft, is characterized in that the current flow through the rotary bridge 4 is adjusted by varying the excitation of the auxiliary alternator 3, 6; this variation is effected through the regulator 7 of the auxiliary alternator by a differential signal Id resulting from the comparison of two currents I1 and I2; of these, I1 is derived from a current i 1  delivered when the vehicle driver closes switch 15, and from a current i 2  delivered by a regulator 18 (see below) linked with the Diesel engine regulator 19; 12 is derived from a single-phase measuring-alternator 20, 21, a current transformer 22 and a rectifier 23, and is an " image " of the main-alternator field current. It is an essential feature of the invention that the diodes 5 and/or their welds of the bridge 4 are protected from the effects of centrifugal force. Second auxiliary alternator.-A second auxiliary alternator 8 is provided, driven, e.g. by a belt from the main alternator shaft and having its field winding 9 energized by the vehicle storage battery 10 through a regulator 11. This second auxiliary alternator provides the excitation current in field winding 6 of auxiliary alternator 3 through the regulator 7 of the latter. The second auxiliary alternator also feeds the regulator 18 linked with the Diesel engine regulator 19 so that the current i 2  is automatically responsive to the action of the regulator 19. The comparison device 12 is a differential amplifier, and each device 13, 14 is either of the magnetic amplifier type or of the thyristor (controlled diodes) type. The measuring alternator has its field winding 20 mounted on the main alternator shaft in series with the field winding 2; its fixed stator 21 is connected across the primary of the current transformer 22. The purpose of the current 12 is to prevent temperature variations in the windings from affecting the generator output. Diode mounting.-Each diode 5 may be secured to a central shoulder 26, Fig. 4, of a disc 27, and the discs, with intervening washers, assembled, on a collar formed at the end of the main alternator shaft, by screwed rods 28. Alternatively (Figs. 2, 3, not shown), the diodes are secured near the periphery of a single annular plate. Power circuit control.-In Fig. 6 (not shown), the main alternator is 3-phase and the primary of a 1-phase transformer is connected across two phases of the alternator power circuit. The voltage developed across the secondary of the transformer is compared in a differential amplifier with a reference voltage to cause a reduction in alternator excitation when its voltage exceeds a predetermined value (to increase the safety of operation). In Fig. 7, two 3-phase armature windings 24a, 24b are provided to energize, through rectifier units 26a, 26b, two D.C. traction motors 28a, 28b, each driving a pair of wheels. The primaries of transformers 25a, 25b of which the secondaries are mounted in opposition, are connected across corresponding phases in each winding, and from the component 27 (e.g. resistance or self-inductance) of the common secondary circuit a signal is injected into a differential amplifier 12 to reduce the alternator excitation in case of unbalance between the power values taken by each of the rectifying units brought about, for example, by slipping of one of the pairs of wheels.