Patent GB-618668-A (GB)
Title: Improvements in and relating to electrical power transmission systems
IPC: H02P9/00
Filed: 1946-11-11
Abstract: 618,668. Transmitting mechanical power; automatic speed control systems. PESTARINI, G. M. Nov. 11, 1946, No. 33452. [Class 38 (iv)] [Also in Group XXXVII] An engine-electric power transmission system, particularly for traction purposes, has, in addition to control means for maintaining a constant engine speed by automatic adjustment of the power output of the generator, means responsive to the generator output current for reducing the power input to the engine when the current exceeds a predetermined value. Means are also preferably provided for automatically reducing the power input to the engine upon the generator voltage reaching a predetermined value. As shown in Fig. 1, motors 2, 3 of a locomotive' are supplied by a metadyne generator 1 driven by an internalcombustion engine having an induction tube 13 and driving also both a metadyne exciter 5 and a critically excited regulating generator 9. Regulation for constant engine speed, by automatic control of the exciting current supplied by machine 5 to the secondary variator winding 4 of generator 1, is provided by a control winding 6 operating on the secondary axis of machine 5 and excited by the voltage difference between the regulating machine 9 and a constant voltage source 7, 8. A winding 20 adjustably energized from the source 7, 8 through a rheostat 19 provides the main secondary excitation for machine 5. A further rheostat 11 in the field circuit of the regulating generator 9 allows adjustment of the engine speed. This rheostat is preferably controlled conjointly with both rheostat 19 and the main throttle 12 of the engine. A further throttle 15 is normally maintained wide open by the combined action of a spring 24 and a torque motor comprising a moving winding 16 energized directly from the source 7, 8 and a fixed winding 18 energized from the same source over rheostat 19. Fixed windings 21, 22 energized, respectively, in proportion to the main generator volts and current, oppose the winding 18 of the torque motor and reduce the throttle opening upon the current or voltage of the generator exceeding pre-arranged values. The two throttles may be replaced by a single one subject both to automatic control by the torque motor and manual control together with the rheostats 11, 19. The winding 6 of the exciter 5 may be supplied solely by the regulating generator when the last is a series-wound machine. In a modified torque motor the moving coil is in the form of a D.C. armature and operates the throttle 15 through a worm drive. When the main generator 1 is not a metadyne, the voltage-responsive winding 21 of the torque motor may be energized from the primary circuit of the exciter 5 if there is provided on its secondary axis a component of excitation opposing winding 6 and proportional to the current of the main generator. In another arrangement the prime-mover drives (1) a main metadyne generator for feeding the traction motors, (2) the regulating generator and (3) a shunt machine with automatic voltage regulation for operating constant voltage apparatus as well as for use in connection with the regulating generator in the control of metadyne exciters for the main generator, as in the arrangement of Fig. 1. The constant voltage source also supplies a shunt motor driving three metadyne machines, one of which excites the fields of the traction motors in proportion to the motor current. The second machine operates, during motoring, to provide excitation on the secondary axis of the main generation as in the arrangement of Fig. 1, whilst the third machine is used for providing excitation on the primary axis of the main generator during rheostatic braking (see Group XXXVII).