| 摘要 |
1,136,407. Limiting rate of change of voltage; ramp generators. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 1 April, 1966 [2 April, 1965], No. 14182/65. Headings H3P and H3W. [Also in Division G3] In a system, particularly for controlling the speed of a lift, in which a step voltage control function is converted into a ramp function, the step voltage is fed to an integrator A2 via a current limiting circuit D, the limiting value of the current limiting circuit being gradually increased from zero on occurrence of a step control voltage so as to limit the first and second differentials of the output ramp function. As shown, the acceleration and deceleration of a lift are respectively controlled by energizing and releasing a relay SR (coil not shown). On energizing relay SR, contacts SR/1 feed a voltage step via amplifier A1 to a Miller integrator A2. Contacts SR/3 switch a previously discharged capacitor C1 across part of a potential divider R11, P4, R14, R12 so that as capacitor C1 charges it gradually increases the current limiting value of a diode bridge D so as to limit the rate of change of current fed into the integrator A2 and hence the second differential of the output ramp function at V2. When capacitor C1 becomes fully charged, the input current to the integrator A2 remains constant at a value determined by capacitor C1 until the output voltage V2, which is fed back via resistor R2, reaches a value such that the input to amplifier A1 is nulled. The output then remains constant until relay SR is released when its contacts reverse their positions, discharging C1 and allowing the previously discharged capacitor C2 to provide a similar function so that the output voltage decreases to zero, decelerating the lift. The linearity of the control current from capacitors C1, C2 may be improved by a further diode bridge in series with bridge D.
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