Abstract: In an AC elevator system employing a three-phase induction motor for driving an elevator car, the primary voltage supplied to the induction motor is controlled to control the motoring torque in the acceleration mode and in the rated-speed running mode, while, in the deceleration mode, a power converter unit supplies AC power of low frequency to the induction motor to apply regenerative braking.

Abstract: A pulse generator is coupled to a car drive motor directly coupled to a sheave, over which a rope suspending an elevator car is passed, and the position of the car is calculated through the counting of pulses produced from the pulse generator. First and second car position detectors for detecting respective first and second car positions are provided within a hatchway, and the number of pulses produced during a period from the actuation of the first car position detector till the actuation of the second car position detector is detected. A count value for calculating the car position is corrected according to the difference between the detected pulse number and a reference pulse number corresponding to the distance between the first and second car position detectors, thereby effecting the compensation for the wear of the sheave and rope to improve the precision of the car position detection.

Abstract: An abnormal speed detector for an elevator system having an elevator car for servicing a plurality of floors, means for driving the elevator car in response to a speed command and a speed detector for detecting a running speed of the elevator car is disclosed. The abnormal speed detector comprises means for storing a set of speed data indicating a predetermined abnormal speed checking pattern as a function of running time or running distance of the elevator car, means for reading out of the storage means one of the set of speed data corresponding to an instant value of the running time or running position of the elevator car after the start of run, and means for comparing an actual speed of the elevator car with the readout speed data to determine if the speed of the elevator car is normal or not.

Abstract: In an elevator control system, in which the elevator car is controlled on the basis of elevator car positions obtained through the counting of distance pulses provided in proportion to the distance travelled by the car and floor height data indicative of the heights of individual floors, the distance pulses are counted by moving the car at a low speed from the lowest floor to the highest floor, and the count at the time of the actuation of a floor position detector, which is actuated when the car passes by each floor, is stored as the floor height value of that floor in a RAM (Random Access Memory). With this arrangement, the measurement of the floor heights is facilitated, and also the preparation of a ROM (Read-Only Memory) for storing the floor height data for each elevator car is made needless to promote the standardization.

Abstract: A bridge circuit including a couple of thyristors and a two diodes is connected between a three-phase ACpower supply and a three-phase induction motor for driving an elevator car. The bridge circuit is adapted to make up a controlled rectifier circuit or an inverse-parallel connection circuit of thyristors, as the case may be, by switching a plurality of contactors. At the time of starting and accelerating the elevator car, the bridge circuit is changed to constitute an inverse-parallel connection circuit of thyristors to which a signal for a sufficiently high speed command is applied. This speed command is applied to a phase shifter, which fires the thyristors in inverse-parallel connection at a sufficiently large conduction angle. In consequence, the three-phase induction motor produces a sufficiently large accelerating torque, so that the car is accelerated according to differences between the accelerating torque and the elevator car load torque.