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.

Abstract: A driving system for moving paths or escalators which use an endles chain adapted to be circulated between a path for transporting passengers, comprising a first and a second sprocket disposed at one end portion and substantially middle portion of the path, respectively, a first and a second induction motor coupled respectively to the first and second sprockets and each having the same rating output the sum of which is selected to be substantially equal to a maximum capacity of the system, an induction coupling interposed between the second sprocket and the second induction motor, means for detecting a current flow through the first induction motor, means for setting a reference value, and a thyristor amplifier for exciting the induction coupling in response to an excess developed when an output of the detecting means exceeds the reference value.