Patent GB-190326465-A (GB)
Title: Improvements in Systems of Electric Motor Control
Filed: 1903-12-03
Granted: 1904-12-03
Abstract: 26,465. British Thomson-Houston Co., [General Electric Co.]. Dec. 3. Motors, controlling.- Relates t o systems in which controllers of the separately-actuated contact type are employed. The contacts are operated automatically in succession to cut out resistance &c. Two circuits are provided for the actuating-coils of the contacts, one an actuating and the other a maintaining circuit. The master - controller contacts are arranged as described in Specification No. 20,755, A.D. 1902, so that the actuating-circuit may be opened and the progressive operation o f t h e motor-controlling c o n - tacts stopped without opening the maintaining- circuit, thus operating at any desired speed. The automatic progression is controlled by an overload relay, so that the resistances cannot be cut out too quickly, the actuating- circuit being opened but the maintaining-circuit closed. An underload relay is also provided for opening the actuating-circuit when the current falls below the limit. Fig. 1 shows the general arrangement of the circuits and switches, in which C indicates the master-controller, 1, 2, 3,4 the train wires, T<1>, T<1>, R<1> to R<9>, S, and P, P the separately. actuated-contacts, K the underload relay, H the series-parallel controlling relay, E the overload relay, and M<1>, M' the motors. Fig. 2 shows the construction of the overload relay E, which has two windings 42, 43. Its core 74 has a portion 74<a> of carbon or like self-lubricating material fitting closely in the tube 74<b>, and has a stem 75 passing through a hole in a lever 78 carrying a switch contact-lever 80. When the core is raised, collars 76, 77 engage the lever 78 and raise it, so breaking contact. This lost motion allows a short interval before the contact is broken. To prevent too sudden a fall of the core when the circuit is opened, a ball valve 72<c> is provided in the fixed core. The lever 78 is held in the open or closed position by a spring 82. Figs. 4 and 5 show the construction of one of the contactors, and are numbered to agree with the contacts R<3> of Fig. 1. The core 92 is pivoted to a lever 94 pivoted at 95 and carrying an insulating-bar 101 upon which are mounted spring contact-fingers d, d<1>, d<2>, d<3> adapted to engage contacts on a fixed block 102. These contacts are arranged to bridge the contacts 28, 28 and 15, 15, or 53, 53 and 16, 16, according as the coil 88 is excited or not. The springs are so arranged that contact is made by one pair before the other pair has left the corresponding contacts. The main contact-arm 97 is pivoted on the lever 94 at 96, and is connected thereto by a spring 100 so that spring contact is maintained. These switches serve, on making the main contact, to cut out the resistances 6, 7, &c., to open the actuating-circuit, and close a maintaining-circuit, at the same time closing the actuating-circuit through the next magnet, provided that such circuit is not open at the contacts 44 of the overload relay E. As shown, the master-controller has four positions. s<1> is the starting position with the motors in series, and s<2> is the running position, the resistances being automatically cut out. At the position P<1> the motors are connected in parallel by the action of the switch H, and at p' the resistances are automatically cut out. The contacts are so arranged that, should the controller be thrown immediately to the parallel position, the motors are automatically connected first in series, the resistances are then cut ont, and finally the motors are connected in parallel.