| 摘要 |
550,387. Rectifying alternating currents ; controlling D.C. motors. ELECTRIC CONSTRUCTION CO., Ltd. Jan. 22, 1942, No. 1012/41. [Class 38 (ii] [Also in Group XXXVII] ln a motor control system in which the armature MA of a D.C. motor is supplied from an A.C. source through the main anodes a of a mercury arc rectifier, the field winding MF is supplied through the exciter anodes e, a resistance 9 being connected in parallel with the motor field at starting. The voltage applied to the motor armature may be regulated by a tapping switch 11 on an auto-transformer 8, the tapping switch being arranged to cut-out the resistance 9 from the exciter anode circuit when it is moved away from the lowest voltage or starting position. This movement also breaks at contacts 10a the circuit of the starting coil 2 associated with the starting electrode S. The starting and exciter anodes circuits are supplied respectively by secondaries 7, 6 coupled to the auto-transformer winding 8, and a relay 3 is provided to open the starting circuit when normal exciter anode current is established. A polyphase arrangement is described with reference to Fig. 2 (not shown) in which regulation in the armature circuit is effected by grid control of the rectifier. In this arrangement, a manually operated rheostat is provided in the field circuit, and a voltage-dropping resistance is connected in series with the field and its starting shunt resistance.
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