| 摘要 |
613,415. Master control of D.C. motors. GENERAL ELECTRIC CO., Ltd., CROFT, E. H., and TURRALL, J. C. Dec. 4, 1944, No. 24169. [Class 38 (iii)] An electric motor control system comprises a master controller adjustable over a number of steps to give a progressive increase in motor torque, and means including a device responsive to the speed of the motor adapted to reduce the motor torque to that corresponding to a lower step than the actual setting of the controller when the speed of the motor exceeds a predetermined value, the said means also being arranged to prevent a resumption of control by the controller over its higher steps until the controller has been adjusted to a predetermined lower step. A motor 4 is adapted to be a ccelerated by movement of a controller 31 to cut out a series starting resistance 7, de-energize a shunt field winding 6 and weaken a serie field winding 5 through the parallel-connected resistors 8 and 9. Rheostatic braking is prc vided by a controller 32, the armature being connected in a closed circuit with a part of the resistor 7 and a part of the series field winding 5, and the shunt field winding 6 being excited from the mains in series with a variable resistor 10. If the controller 31 is in its eighth, ninth or tenth position, and contacts 35 are closed by a speed-responsive device, a relay 37c is operated so that the shunt field winding is reconnected and full series field excitation is obtained, the motor operating, in effect, as in the seventh position of the controller. The relay 37c closes contacts 37NO2 in parallel with contacts 35 so that the relay is held energized until the controller is moved back to the seventh or a lower position. In a modification, the relay 37c is replaced by one having a first coil energized over the contacts of the controller and a second coil energized in dependence upon the operation of the speedresponsive device. Energization of both coils is necessary to operate the relay, but energization of the first coil alone is sufficient to maintain it.
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