Patent GB-190701279-A (GB)
Title: Improvements in Systems of Electric Motor Control in which the Characteristic of the Main Generator is Varied and in Apparatus therefor.
Filed: 1907-01-17
Granted: 1908-01-16
Abstract: 1279. British Thomson-Houston Co., [General Electric Co.]. Jan. 17. Motor control systems; switches.-In a system where a generator driven by a prime mover supplies current to one or more motors, a line switch completes the circuit between the generator and motors, and is provided with means to .deter,- mine the extent of movement of a switch which cuts resistance out of the field circuit of the generator. A switch to connect the motors in series or parallel is interlocked with the line switch so that it can only be moved when the line switch is in the 'off' position. Controllers C, C<1> are placed at each end of the car, and each has a mainline switch D, a resistance switch E, and a seriesparallel reversing-switch F. The field coils of the generator G are connected to an exciter g, and the circuit includes a resistance R, parts of which may be short-circuited by the contact-member 18 of the switch E. The contact-arm 18 is carried on a stem 19 attached to a piston 20 in the cylinder 21, and this apparatus acts as a dash-pot. The stem 19 is connected to the arm 22 of a bell-crank lever, the other arm 24 of which has a roller 25 engaging a cam 26 on the shaft of the main-line switch D. In the position shown, the cam 26 holds the lever 22 so that the contact 18 bridges contacts 1, 1<a>, the latter being dead. As the line switch D is rotated, its connexions remain unchanged, but the cam permits the piston 20 and contact 18 to drop. This operation may take place step by step; or the line switch may be moved to its last position., and the contact 18 then falls under the control of the dashpot. An electro-magnet. 27, when energized, attracts the stem 19, or an armature on the stem, and so prevents further movement. The circuit of the electro-magnet 27 is controlled by a throttle relay 28 in the circuit of the armature of the generator G. The car is started by turning the handle 53, Fig. 3, of the swith F, say to the left in the drawings, and bringing the switch D to its first running position. A current flows from the lefthand terminal of the generator armature, through switch 30, conductor 32, contacts d<4>, d<8>,d<7>, d<3>, conductor 33, field of motor M<1>, conductor 34, contacts f<8>, 8<f>, f9 of switch F, through conductor 35, armature of motor M', conductor 36, contacts f<7>, 7<f>, 9<f>, f<10> of switch F, conductor 37, field of motor M, conductor 38, contacts f<3>, 2<f>, f<2>, conductor 39, armature of motor M, conductor 40, contacts f<4>, 3<f>, 1<f>, f<1>, conductor 41, contacts d<1>, d<5>, d<6>, d' of the line switch D, blow-out coil BC, conductor 42, and throttle relay 28, to the right-hand terminal of the generator armature. The motors M, M<1> are thus connected in series, and the speed is increased by moving the line switch D to its second running position to allow the contact 18 to bridge contacts 1, 10. This short-circuits that part of the resistance R between the taps 43, 44, so that the exciting-current in the generator field is increased. In the third running position of the line switch, ,the contact 18 bridges contacts 2, 10 and short-circuits more resistance. The entire resistance R may be removed step by step in this way. If too much current is supplied to the motors, the throttle 28 is actuated, and the switch E is locked by the electro-magnec 27. Further control may be obtained-by moving the line switch D to the 'off ' position and the switch F to its second position. The motors M, M<1> are then connected in parallel, and the resistance R may be gradually short-circuited as before. To reverse the motors, the switch F is turned in the opposite direction. To ensure the line switch D being brought back to its ' off' position before the switch F can be operated, its shaft carries a disk 55, Fig. 4, .with a notch-56. The switch F is provided with a notched disk 57. In the 'off' position of the switches, a dog 58 engages the notches 56, 59 and locks the switch D, but the switch F may be operated, thereby forcing the dog 58 farther into the notch 56 against the tension of the spring 60. As the switch F moves, the dog 58 is moved by the spring 60 into one of the notches 61, 62, 63, 64, and the main switch D is then unlocked.