Motor control system for lifts - includes blending unit for continuously combining two independent circuits connected to tachometer output

摘要

The lift control system includes a control for the controlled three phase motors, using a voltage dependent mixing controller, which during a section of the operation of the travel indicating diagram, continuously varies the effect of two independent control circuits. This action is controlled by the output voltage from a tachometer. The tachometer is connected to two independent circuits each with a system of comparators connected to two sections of the mixer in series with each other. Another branch from the tachometer is connected to the input of the mixer, which similarly incorporates a sys tem of comparators connected to an operational amplifier at its output.