Hitachi, Ltd.

Yasuyuki Maeda

Katsu Komuro

Nobuo Mitsui

Sadao Hokari

Tadao Kameyama

Seiya Shima

Takanobu Hatakeyama

Tomiaki Kurihara

Akinori Watanabe

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.

AC Elevator control system

A control system for an AC elevator system in which an actual speed of an elevator car is compared with a speed command and control is made so that deviation between the actual speed and the commanded speed becomes zero. The speed command is so composed that deceleration of the elevator car is gradually decreased as the car approaches to a target landing position in the stopping operation of the elevator. A motoring torque or a braking torque is additionally generated in dependence on a load on the car in a region close to the target landing position.

In a three phase load controlling system two bilateral switching circuits control the current in the first and the third phases; the first phase is later than the third. The second phase is uncontrolled. The gating signals applied to the bilateral switching arrangement connected in the first phase are advanced by a constant degree with respect to the voltage of the first phase. The gating signals applied to the bilateral switching arrangement connected in the third phase are synchronized with the voltage of the third phase.

Three phase controlling system

In an a-c elevator, an elevator car suspended by ropes is driven by an induction motor for vertical movement. A system commonly used for controlling the device including thyristors connected in parallel with opposite polarities across a three-phase a-c power source and the induction motor for controlling the motoring torque produced by the induction motor, a bridge rectifier including a thyristor for supplying direct current to the induction motor for controlling the braking torque produced by the induction motor, and means for controlling the operating phase of the thyristors in the thyristor device and the thyristor in the bridge rectifier depending on the error between the instructed speed and the actual speed of the elevator car. When the elevator car stops at a target floor and passengers get on and off the elevator car, the variation in the load of the elevator car results in an increase or decrease in the length of the ropes thereby giving rise to an error between the floor level of the target floor and that of the elevator car. A levelling apparatus is provided which comprises a position detector detecting this level error in either direction, and a level correction speed pattern signal generator generating a level correction speed pattern signal in response to the appearance of an output from the position detector, so that the operating phase of the thyristors in the thyristor device and the thyristor in the bridge rectifier can be controlled depending on the error between the level correction speed pattern and the actual speed of the elevator car.

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Katsuta, Japan

Yasuyuki Maeda