Patent GB-190311730-A (GB)
Title: Improvements in Systems of Electric Motor-control.
Inventor: CAROLAN EDGAR ALFRED
Filed: 1903-05-22
Granted: 1904-05-19
Abstract: 11,730. Carolan, E. A., [General Electric Co.]. May 22. Motors, controlling.-In a contact system for a motor used in operations such as hoisting, driving, revolving turrets and working ordnance, &c., the motor field coil F, Figs. 5, 7, and 11, is connected across the supply mains M', M', in series with a switch S' and a resistance R, R<1>, an increasing part of which is thrown, as the motor speeds up, into the part of the field circuit round which the armature A is shunted, the switch S' being finally opened to connect the armature and field coil directly in series. The braking-characteristics of the motor so connected are similar to those of a shunt-wound motor. The controller consists of two hand-switches C, D, Figs. 7 and 11, held normally open by springs and controlling the circuit-closers G, H, which connect up the armature for forward or backward driving, and of two push-buttons E, E<1> which control the rheostat switch J to increase or reduce the armature speed. When starting the motor by pulling up the handle of the switch C, a circuit is completed from the main M<1> through the switch S on the rheostat, lead 86, disc 33 of the closer H, lead 84, solenoid 36, contacts 17, 18 of the switch C, and leads 65, 60 to the main M', the core 28 of the closer G being then raised. The field coil F is then connected across the mains in the circuit comprising the lead 61, disc 34, leads 100, 99, resistance R', switch S<1>, resistance R, leads 95, 96, disc 30, and lead 60; the arma,ture A is then also in a branch circuit between the rheostat contacts 44, 45, all the resistance being outside this branch. As the switch S is included in the initial energizing-circuit of the solenoids 36, 37, as described above, neither of the closers G, H can be operated unless the rheostat is in the normal position shown in Fig. 7. When a closer has been opened, it can be retained in that position independently of the rheostat, as a circuit comprising the coil F, electrically-connected discs 34, 32, lead 90, resistance 93, disc 33, switch C, and lead 60 is then completed through the corresponding solenoid 36 ; the resistance 93 reduces the current to an amount sufficient only to retain the core 28. When a closer is raised, a circuit is completed through the coil F, discs 34, 32, leads 75, 74, rheostat solenoid 49, half the resistance 79, and the normally-closed push-button E' to the return lead 60, the current in this circuit being insufficient to raise the core 47. If, however, the normally-open button E is pressed down to connect its contacts, the half-resistance 79 is shortcircuited and the current increased sufficiently to raise the core 47, the armature A being then connected through the contacts 44, 45 to intermediate points in the resistance R<1>, R. Releasing the button E reduces the current to an amount sufficient only to hold the core 47 stationary, and pressing the button E' reduces it still further by including all the resistance 79 so that the contacts 44, 45 move back towards their original positions. As the energizing-circuit of the solenoid 49 is dependent upon contacts made by a closer G, H, when in the raised or closed position, the rheostat can only be operated after the operating of one of the closers, and neither closer can be closed unless the other is open. At the end of the rising motion of the contacts 44, 45, the switch S' is opened by a collar 50 to connect the armature and field coil in series. The closer H acts similarly to the closer G, but reverses the armature current to reverse the motor. The switches C, D and buttons E, E' are mounted on the insulating-base of a case 24 having a hinged end cover 25, the buttons being so placed as to be within reach of the operator's thumbs, and the discs 34, 35 are electrically connected in the same way as the discs 32, 34.