An arrangement for feeding a direct-current motor from a.c. mains through grid-controlled rectifier

摘要

748,766. Control of D.C. motors. LICENTIA PATENT-VERWALTUNGS GES. Nov. 21, 1952 [Nov. 22,1951], No. 29476/62. Class 38 (4). [Also in Group XXXVII] The invention relates to speed control of a reversible D.C. motor supplied through a gridcontrolled rectifier, and provides for armature current limiting and regenerative braking. As shown, the armature 1 is supplied through a grid-controlled rectifier 2, and the field 12 is reversibly supplied through rectifiers 13a, 13b. A manual control lever 5 moves contacts over an upper track 4 providing a speed reference voltage and a lower track connected to a field reversing relay 11. The speed error voltage comprises the difference between the armature voltage and the reference voltage from potentiometer track 4 and is applied through a valve amplifier 8 to the grid control device 9. A current transformer 15 in the A.C. supply line provides a signal representative of the armature current which is applied to the grid circuit of the amplifier 8 to apply a limiting bias when its magnitude exceeds that of a reference source 18. At the end position of the control lever 5 resistance is introduced into the field control circuit to increase the motor speed. Contacts 20a, 20b are operated by a relay 23 across the motor armature or a relay 22 in the grid control circuit to short-circuit these field control resistors until full armature voltage is established. In a modification, Fig. 2 (not shown), regenerative braking is used to slow the motor for reduced speeds (instead of for reversing only), and a step-by-step relay controlled by a relay 27 in the grid control circuit reverses the polarity of the field every time the error signal falls to zero.