Abstract: An AC motor control system and process useful in such AC motor applications as elevators, storage retrieval machines, cranes and hoists, and other load-carrying and work performing machinery.Two identical and electrically isolated windings are utilized in an AC motor with the current to each winding being controlled through an SCR bank. A first winding, when energized, sets up an electromagnetic field which drives the rotor in a clockwise. A second winding, when energized, drives the rotor in a counterclockwise direction.The use of two separate motor windings eliminates line-to-line electrical short circuit problems so that expensive lock-out circuits, circuit breakers, current feedback detectors and air chokes are no longer required.

Abstract: An apparatus and method for automatic leveling of elevator cars by controlled DC plugging of AC induction motors. The invention utilizes, in a novel circuit and control arrangement, the external neutral connection of a Y-wound motor design to inject controlled direct current into the neutral to dynamically control the braking to a stop. The elevator car is thus more safely and accurately leveled at the desired floor than has heretofore been known in the art. A novel speed control method is also disclosed which compares and sums positive and negative DC signals and which switches to the motor braking mode at a desired time.