Patent GB-191129138-A (GB)
Title: Improvements in Controllers for Electric Motors.
Inventor: TURNER PERCY STUART
IPC: H01H9/26
Filed: 1911-12-27
Granted: 1912-12-23
Abstract: 29,138. Turner, P. S. Dec. 27. Systems for continuous-current motors only ; controllers, brake devices and interlocking- devices for. -A motor controller for series motors, particularly of the kind used for cranes where a fine graduation of speed is required with varying loads, is provided with a shunt resistance in parallel with the armature, which resistance can be varied independently of the resistance in series with the motor to varv the speed. The controller is so arranged that the shunt circuit can only be completed when a certain amount of resistance is included in series with the armature, and the series resistance can be varied when the shunt circuit is broken, or within limits when this circuit is closed. The controller in the preferred form comprises two drums 1, 2, Fig. 2, for varying the series and shunt resistances respectively, provided with the usual notched plate 7, 8 and pivoted arms 9. 10. In addition, there are two cam-plates 11, 12 and an interlocking spring-controlled bolt 13 contained within a casing 15 attached to the top plate of the controller. A roller 14 on one end of the bolt 13 engages a notch 26 in the cam-plate 12 in the off position, and the other end of the bolt is adapted to enter a recess 20 in the cam-plate 11, which is provided with removable pieces 21. To vary the speed of the motor, the shunt drum is moved to the first operative position in the direction of the arrow 27, in which position a shunt circuit of low resistance is completed around the armature, and the. series drum is moved to the first or second position. The speed is further increased by moving the shunt drum until, in its last position, the maximum amount of resistance is inserted, and the drum is then moved to the ' off ' position as shown. During movement of the shunt drum, the roller 14 rides up on the cam-plate 12 and forces the bolt 13 into the recess 20, so that the main drum can only be operated from the ' off ' position to the first one or two positions on the hoisting side. When the shunt drum has been operated, the speed may be further increased by moving the main drum to its remaining operative positions, the bolt 13 riding on the cam-plate 11 so causing the roller 14 to engage the notch 26 and prevent rotation of the shunt drum. The notched plate 7 on the drum 1 is provided with its last notches 22, 23 formed to prevent rotation beyond the last operative positions on the hoisting or lowering side, and the notched plate 8 on the drum 2 is provided with notches 24, 25 at the ' off ' and first operative positions, to prevent rotation of the drum except in one direction only, and to prevent the shunt circuit from being broken except with the maximum of resistance inserted therein. On the lowering side, the shunt drum is not operable, as the pin 13 rides on the camplate 11 and so locks the shunt drum by means of the roller 14 and notch 26. In order to allow the shunt drum to be operated during the lowering positions as well as during hoisting, the modification shown in Fig. 4 is used. The series drum has a recess 30 of greater depth and another recess 31 of less depth. Removable pieces 32, 33, 34 are provided. The size of the cam-plate 35 on the shunt drum is increased at 36 corresponding in position to the deeper recess 30. The operative positions on the shunt drum are arranged in reverse order to the previous case, and a notch 38 is provided so that the drum cannot be moved from its ' off ' position, as shown, in the wrong direction, that is to the last operative position in which the minimum amount of resistance is in shunt, and a notch 39 is provided to prevent the reverse, that is, moving from the last position of minimum resistance to the ' off ' when the circuit is broken. The operation of this controller on the hoisting side is the same as in the previous case, except that the shunt drum has to be operated in a reverse direction, i.e. from the last position of minimum resistance to the ' off ' position, so that, before the current is broken, the maximum resistance is inserted. When the main drum 1 has been moved to the positions on the lowering side, usually the last positions, corresponding to the recess 31, the shunt drum can be rotated in the direction of the arrow except in those positions in which the part 36 of the cam-plate 35 engages the roller 14, as the recess 31 is not deep enough to allow further movement of the bolt 13, so that the resistance in the shunt circuit when lowering cannot be reduced beyond a predetermined amount in those positions corresponding to the braking positions of a controller. On lowering, the main drum inserts resistance and forms a short-circuit round the motor until the position is reached when the shunt drum can be operated to decrease the resistance, the amount of which cannot be reduced beyond a certain degree, to stop the motor. In place of a controller having two drums, two separate controllers may be used; or the two drums may be arranged on the same shaft and interlocking mechanism provided ; or other type of switching- mechanism, or a pivoted arm may be used in place of an interlocking bar; or an electrical interlocking arrangement may be used. In another modification, the series contacts may be extended in certain positions, and additional contacts provided for operating the shunt circuit.