Patent GB-333012-A (GB)
Title: Improvements in or relating to electric power plants for running-in fluid pressure engines
IPC: G01M15/04
Filed: 1929-06-24
Abstract: 333,012. General Electric Co., Ltd., and Wilson, W. June 24, 1929. Running generators in parallel; starting prime movers.-Electric power plant for running-in fluid pressure engines, such as automobile engines, comprises a dynamo-electric machine adopted to be driven by an engine under test and to supply electric power to a power supply system having a separate source of supply. Means are provided fer preventing the machine from driving the engine with appreciable force in the event of the power developed by the engine falling to a value too low to cause the machine to generate. The machine, after interruption, is automatically caused by a polarized control relay to generate again into the system when the engine has picked up. The machine first runs as a motor driving the engine, and after completion of a predetermined number of revolutions at different speeds is driven by the engine and generator on light load through a bank of resistances. The machine is then connected, by means of the polarized relay, so as to generate into the supply system. In the system shown in Fig. 1, the operation is manually controlled by three push-buttons when switch 161 is closed and by the polarized relay when switch 161 is open. A sequence drum 146 is geared by reduction gearing to the machine shaft through a friction clutch and is constructed with a number of rings 148 - - 155 fitted with segments which make contact in order with brushes connected to the control circuit. The connections to the drum are arranged to signal the correct setting for the required direction of rotation of the machine and to cut out the resistances 124, 125 and 126 in the armature circuit as higher speeds are required. Two contactors 128, 157 mechanically interlocked so that both cannot be closed simultaneously, close the armature circuit. Two overload relays 123, 156 are included in the respective circuits when the machine is motoring and when generating through the resistance. The relay 123 is also in circuit when the machine is generating to the power supply system. Contactor 128 is closed when push-button 162 is depressed and motoring commences. Push-button 217 restarts the machine at the stage where interruption takes place when this is required-interruption being effected by pushbutton 186. Further depression of this button on to contacts 184 closes contacts 157 and allows the machine to generate through the resistance. The contactor 130 cuts out section 126 and the bank of resistances when the armature current has dropped sufficiently to allow current-limit relay 122 to close the contacts 178. The further sections of the bank of resistance are short circuited by contactors 131, 132 which are mechanically interlocked with contactor 130 so that closure must follow in correct sequence. Signal lamps 198 - - 202 show the stage of operations and lamps 143, 144 show whether the sequence drum is in the correct position before motoring commences. The shunt field winding 112 is in series with resistance 113 which is mechanically interlocked with contacts 116 in the control circuit so as to prevent closure of contactors 128 or 157 when the shunt field is weakened. The control relay has a series winding 121 and shunt winding 174 and auxiliary contacts 167 and 168 which are bridged to close the operating coil circuit of contactor 128 when the switch 161 is open and the machine generating. Auxiliary contacts 176 close a signal-lamp circuit when machine is generating to the supply system. The relay is biassed by a spring and may be arranged to operate its contacts when a predetermined small current flows from the machine to the mains or vice versa. In the arrangement shown in Figs. 2 and 3, the polarized control relay comprises an armature 171 which is polarized by a winding 172, or may be permanently magnetized. The armature 171 is pivoted at 170 and biassed by a spring 1 of adjustable tension so that the moving contacts 169, 175 are in the open position. A soft-iron member 12 is rigidly secured to the armature 171 and makes contact with the armature at its upper surface. The limbs of the members 12 extend downwards on the outward side of pole pieces 173 of an iron yoke 2. A series winding 121 and shunt winding 174 are wound on this yoke 2. One terminal of the shunt winding 174 is electrically connected to the moving contact of the contactor 128 and the other terminal of the winding to the fixed contact of contactor 128 through the current limit relay winding 122, series field winding 117, the overload relay winding 123 and through either the contactor 132 or a section or sections of the bank of resistances. A protective relay comprising a coil 4, Fig. 1, connected in parallel with the shunt winding 174 and an armature adapted to operate a moving contact 5 which breaks the circuit of winding 174 at contacts 6 protects.the shunt winding in the event of the voltage across it exceeding a desired value. The winding 174 and coil 4 may also be connected directly across the contacts of contactor 128. The series winding 121 would then be connected between the fixed contact of contactor 128 and the moving contacts of contactors 130, 131, 132.