Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1976-04-27
1978-04-11
Dobeck, B.
Elevator, industrial lift truck, or stationary lift for vehicle
Stationary lift for roadway vehicle or required component...
Having specific drive means for support
B66B 128
Patent
active
040834310
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. 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.
REFERENCES:
patent: 3613835 (1971-10-01), Vizzotto
patent: 3627080 (1971-12-01), Yuminaka et al.
patent: 3708734 (1973-01-01), Rowe
patent: 3777855 (1973-12-01), Boyldew et al.
patent: 3918552 (1975-11-01), Kameyama et al.
Kurihara Tomiaki
Oohira Takeshi
Dobeck B.
Duncanson Jr. W. E.
Hitachi , Ltd.
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