| 摘要 |
<p>1454871 Automatic control of speed GENERAL ELECTRIC CO 27 Feb 1974 [6 March 1973] 8939/74 Heading G3R A D.C. motor, fed from an A.C. source through a full wave rectifier bridge with controllable rectifiers in each leg, has its speed regulated according to the error between a reference value and a speed dependent voltage across the motor armature, the error being switched to a firing angle control device for the rectifiers when the sensed armature current is zero. The firing angle of the rectifiers is thus determined by the motor speed error at zero armature current i.e. when the IR drop of the armature is zero. The voltage across the armature is then a true representation of the motor speed and errors due to the armature IR drop are eliminated. As shown, the full wave rectifier bridge comprises thyristors 42, 44, 46 and 48 and the field 16 of motor 28 is energized from a second bridge 12. At zero armature current, as sensed by resistor 50 or a magnetic amplifier, switch 66 is enabled to allow a motor speed error signal to thyristor control 32. The speed error is formed by comparator 58 from the actual speed i.e. the armature voltage of D.C. shunt motor 28, as measured using divider 52, 54, and from a reference valve from potentiometer 61.</p> |
