Hitachi, Ltd.

Takeshi Oohira

Katsuya Teranishi

Nobuo Mitsui

Tomiaki Kurihara

Akinori Watanabe

Kazuhiko Kawauchi

Shoichi Nakao

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. When the accelerated car reaches a deceleration-starting point, the speed command in changed to another command decelerating the car at a predetermined rate toward a destination. At the same time, the phase shifter is changed over to receive a deviation signal between the speed command signal and the output signal of the tachometer generator connected to the motor. The inverse-parallel connection of thyristors is changed over to the controlled rectifier circuit connection. The motor is thus decelerated by a speed feedback control system of a DC braking type.

Elevator control apparatus

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.

Driving system for moving paths or escalators

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Katsuta, Japan

Takeshi Oohira