GB513814A - Improvements in and relating to controllers for electric motors - Google Patents

Abstract

513,814. Master control of D.C. motors. IGRANIC ELECTRIC CO., Ltd. July 26, 1938, No. 22182. Convention date, July 30, 1937. [Class 38 (iii)] Non-regenerative braking.-Rheostatic braking circuits for series motors A, A', comprise closed loops each including the armature of one motor and the field of another, means being provided to vary the resistances of the loops, and certain of the reductions of resistance being subjected to a predetermined time delay. With a controller 33 in its off position the rheostatic braking circuits are completed with a resistance R' in one circuit and a resistance R" in the other. Movement of the controller to either of its positions 1 de-energizes contactors 27, 28, so that resistances R<3> and R<13> are added to the respective braking circuits. Upon further movement of the controller contactors 25, 26, are energised to add further resistances R<2>, R<12>, to the braking circuits. Further movement of the controller energizes contactors 20, 21, 22 and 23, to interrupt the braking circuits. The position to which the controller is returned to effect braking is selected in accordance with the speed at which the motors are operated. When the controller is moved back towards its off position, the switches 20, 21, 22, 23 complete the braking circuits with all resistance inserted, and although movement of the controller position 1 opens the energizing circuits for contactors 25, 26, these circuits are maintained by a switch 31. A coil 31a. operating 'the switch 31 is energized when the controller occupies its position 1, but a winding 31b short-circuited by de-energization of the switches 20, 21, 22 and 23, prevents opening of the switch 31 for a predetermined time. When the switch 31 opens, contactors 25 and 26, short circuit resistances R<2>, R<12>. In the off position of the controller contactors 27, 28 are energized to short-circuit resistances R', R", subject to control by relays 29, 30, which must reclose in response to the decrease of braking current before the contactors 27,. 28, are energized. These contactors 27, 28, are controlled by the relays 29, 30 to reinsert the resistances R', R", if the braking current subsequently exceeds a predetermined value. Upon failure of power the braking circuits are established with an intermediate value of braking resistance. In a modification, Fig. 4, not shown, the braking control is effected by a separate controller, which in operation from an off position sets up the braking circuits and excludes the resistances R<2>, R<12>, and R<3>, R<13> in steps.