GB836130A - Improvements relating to the control of electric traction motors - Google Patents

Abstract

836,130. Control of motors. SOC. GENERALE DE CONSTRUCTIONS ELECTRIQUES ET MECANIQUES ALSTHOM. Nov. 2, 1956 [Nov. 4, 1955], No. 33514/56. Class 38 (3). In a traction system, the armature of each motor is shunted during the early stages of the starting operation in order to reduce the tendency towards wheel slippage. As shown, on the first notch of a master controller, contacts 11, 18, 18<SP>1</SP> are closed together with the resistance contacts 17, 17<SP>1</SP> so that the line current initially passes through all the sections of resistor 3 except the last which is shunted across the armature 6 of a first series motor. The current then passes through the contact 11 to a second motor which is connected in a manner similar to the first. The series resistor 3 is then progressively reduced to a predetermined value, the armature shunting resistance remaining unchanged. Thereupon the shunt resistance is increased, and this operation is followed by the opening of contacts 18, 18<SP>1</SP> to interrupt the shunt circuit before all the series resistance has been removed. Transition from series to parallel connection of the motors is effected by the shortcircuit method, and, after the motors have been connected in parallel, either the shunt resistors may be restored or the shunting of the motors dispensed with. In another arrangement, the vehicle is provided with motors connected in series pairs, each motor of a pair being preferably provided with an individual shunting resistance. This reduces the tendency to wheel-slip especially if the motors are supplied from a generator having a voltage-characteristic of decreasing slope, Fig. 5 (not shown). The motors may be of the direct-current or single-phase types. In the latter case each entire motor (including its field winding) is shunted by the resistance. Specifications 347,656 and 724,412 are referred to.