Improvements in or relating to electric motor control systems

摘要

957,113. Rectifying; control of D.C. motors. MARCONI CO. Ltd. Oct. 3, 1962 [Nov. 29, 1961], No. 42739/61. Headings H2F and H2J. [Also in Division G3] A reversible motor M is supplied from a three-phase source through transformer TR2 and controlled rectifiers S1-S12 associated with trigger pulse generating units 1P-6P having A.C. inputs derived from transformer TR1 whose secondary windings F, AF are in phase opposition. The slider of potentiometer PC may be displaced to apply a positive potential to the base of transistor N2, the base of transistor N1 receiving an A.C. input from phase FR/Y. When the base of transistor N1 becomes positive with respect to the base of transistor N2, transistor N2 becomes conductive to render transistor NP2 conductive, a differentiating circuit K2, R2, supplying a negative pulse to the base of transistor N4. Since the emitter of transistor N4 is positive at this time, a pulse is fed through leads T5, T1, to rectifiers S5, S1 which pass current to the motor until the potential across terminals R, Y falls below the back-E.M.F. When the voltage on phase AFB/R rises above the D.C. control potential, pulses from unit 6P trigger rectifiers S6, S1, and the cycle of operations continues in a similar manner. If the slider of potentiometer PC is set to supply a negative control voltage, transistors N1, NP1 conduct when the potential on phase FR/Y becomes negative with regard to the control voltage. Triggering pulses are then delivered to rectifiers S8, S10, for reverse operation of the motor. Thereafter, other pairs of rectifiers are switched-on for rotation in the reverse direction. A voltage representing the back-E.M.F. is delivered from tachometer generator G through potentiometer AP to the base of transistor U1, a voltage from potentiometer PC being applied to the base of transistor U2. If the reference voltage exceeds the feedback voltage, transistors U1, U3, U6 are conductive so that the emitter of transistor N3, and all other emitters on lead A, are at positive potential, the transistor N4 and corresponding transistors being inoperative at this time. Thus, if potentiometer PC is set to a lower speed position, rectifiers S8, S10, for example, are cut off and rectifiers S5, S1, switch on for regenerative braking action until the motor stabilizes at a new speed.