GB349169A - Improvements in and relating to remote control systems for electric motors - Google Patents

Abstract

349,169. Master control of several motors. IGRANIC ELECTRIC CO., Ltd., 147, Queen Victoria Street, London.-(Cutler Hammer Manufacturing Co.; Milwaukee, Wisconsin, U.S.A.) March 7, 1930, No. 7539. [Class 38 (iii).] Travelling to predetermined limits.-Each of the motors A, only one shown in Fig. 3, for opening and closing a furnace door is controlled locally by a drum 13, and by a master controller MC, located on a crane, through a single connection effected by a trolley T3 on the crane engaging a shoe S pertaining to the particular motor. Low voltage relay contacts 26, 27 are closed when both coils 26a, 26b or 27a, 27b of the relay are energized, but will remain closed with normal voltage with only coil 26a or 27a energized. Thus to reclose these relays after operation it is necessary to return the master controller to the " off " position. Movement of the master controller to the " open " position, provided the local controller 13 is "off," connects line L1 through coil 26a to point X, thereby short-circuiting operating coil 12a and lock-out coil 11b of reversing switches 12, 11 respectively, and fully energizing lock-out coil 12b and operating coil 11a. Reversing switches 11 thereupon close and cause closure of main switch 10, whereupon the motor opens the door until the limit switch 14 is opened. Similar circuits are completed in the " close " position of the master controller only line L2 is connected to the point X and an auxiliary contact 12e on the switch 12 completes a maintaining circuit for this reversing switch, so that the crane may proceed to another furnace while the door is still closing. On overload, coils 16a, 17a open contacts 16, 17 in the circuit between the shoe S and the point X, thereby shutting down the motor. These contacts are maintained open by coils 16b, 17b until deenergized by return of the master controller to its " off " position. A modified arrangement of novolt relays is shown in Fig. 4. Relay 40 can only be closed in the " off " position. In either running position, a second relay 41 is closed over contacts 40 and completes an alternative energizing circuit for the relay 40.