Patent GB-105913-A (GB)
Title: Systems of Control for Single Phase Commutator Motors.
IPC: B60L15/38
Filed: 1917-04-12
Abstract: 105,913. British Westinghouse Electric & Manufacturing Co., (Assignees of Hellmund, R. E., Meyer, H. R., and Candee, A. H.). April 12, 1916, [Convention date]. Systems for alternating-current motors only.- In a control system for alternating current motors of the compensated commutator type, the main field and compensating windings are connected for reverse doubly-fed or repulsion connexions at starting and for' normal doubly-fed connexions during running, the accelerating-connexions being controlled by current and voltage limit relays. The circuits of two motors with armatures 14, 18, main fields 15, 19, and compensating windings 16, 20 are shown in Fig. 1, and the actuating-circuits with the controller 46 are shown in Fig. 4. This arrangement gives a reverse doubly-fed connexion for starting. One brush of each armature is connected to the tap 24 of the auto-transformer 22 connected between the trolly line and ground. The other brushes are connected to switches 12, 11 which are closed during starting to connect the brushes to the transformer tap 25. The main field windings 15, 19 are connected to a point on the resistance 27, the ends of which can be connected to various transformer taps by the switches 7 8, 9, 10. The ends of the compensating field windings are connected to the resistance 26 and the voltage impressed on them is varied by the switches 1 - - 6. One of the field circuits includes windings of current-limit switches L<2>, L<3>. and a voltage relay L<1> is connected across the compensating-fields. At starting, the trolly line potential closes the relay 38 and, when the master controller MC is moved to its first position T, the line switch LS, and switches 11, 12 are energized and closed. The switches 1, 2 also are closed, their actuating-circuits being completed through the controller 46. The motors are thus started with a reverse doubly-fed connexion. The switches 11, 12 may close short circuits round the armatures to start the motors as repulsion motors. The controller 46 is operated pneumatically, the ' on ' and ' off ' valves being actuated by electromagnets when the master controller is moved to the position U. The off ' magnet is under the control of the current limit switch L<2> and this enables the controller to move step by step to close the switches 3, 4 and, in the position D, to energize the coils of the switches 7, 8 subject to the lifting of the voltage relay L<1>. This changes the connexion of the armature brushes from the tap 25 to the resistance 27 and the circuit includes the main fields 15, 19, thereby giving the normal doubly-fed connexion. If the voltage is insufficient to raise the relay L<1>, the drum 46 moves forward to open the switch 3 and to close the switch 5. The master controller is then moved to position V and the drum 46 causes the switch 6 to close and the switches 'i, 8 to close independently of the relay L<1>. Switches 9, 10 are then closed to complete the full running connexions. The contacts of the current relay L<3> are normally closed during acceleration, but if the load is abnormally lightened, the contacts open and cause the switches 5, 6, 7, 8 to open. An auxiliary winding 43 acts in conjunction with the main winding of the current limit relay L<2> during the starting period, or the auxiliary winding may lift a small weight from the relay core during the starting operations so that the relay has a lower setting then than it has during running.