Controllers for reversible electric motors

摘要

352,613. Control of motors. IGRANIC ELECTRIC CO., Ltd., 147, Queen Victoria Street, London.-(Cutter-Hammer Manufacturing Co. ; Milwaukee, Wisconsin, U.S.A.) May 6, 1930, No. 13889. [Class 38 (iii).] Continuous reversals.-A motor A driving a planing-machine is reversed by plugging at each end of the stroke and thereafter accelerated by cutting-out series resistance in two stages. Should the means for effecting plugging fail to operate, a dynamic-braking circuit becomes operative, and should the supply voltage fail the motor is selfexcited during dynamic braking. During plugging and accelerating full field strength is used, but it is weakened for running. Normal starting and stopping is obtained by pushbutton control. The operation is briefly as follows. With normal line voltage contacts 9b, 9c are closed and contacts 9d, 9e are open, thus shunt field F3 is fully excited, both field rheostats 11, 12 being shorted. Depression of start pushbutton 19 causes, according to the position of controller 18 operated by the platen of the planer, closure of reversing switches 1, 2 or 3, 4. Thereafter resistance R1 and part of series field F1 is cut out, then resistance R2 is cut out and one of the rheostats 11, 12 is inserted in the shunt field circuit according to the direction of motion. At the end of the stroke the controller 18 is moved to its other position causing opening of the pair of reversing switches that were closed and the closing of the other pair so as to plug the motor, the resistance R1, R3 being reinserted in the armature circuit and the rheostat excluded from the field circuit, whereupon acceleration in the reverse direction proceeds as before. If either pair of reversing switches fail to complete the plugging connection, a switch 7 normally held open, closes with a time delay and completes a dynamic braking circuit through the resistance R3. Should the supply voltage fail, contacts 9b, 9c open and contacts 9d, 9e close to connect the shunt field F3 to the armature and switch 7 closes to complete the braking circuit. The field is connected in the appropriate direction to the armature through contacts 10b, 10c or 10d, 10e, these contacts being opened or closed in pairs after each reversal of the motor and according to the direction of rotation by means of a coil 10a. A stop pushbutton 20 or overload coil 29a controlling contacts 29 is operative to stop the motor. Inching pushbuttons 21, 22 for each direction of running, only cause acceleration steps to proceed as far as the cutting out the resistance R1 and field F1.