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World's First Inverter-Controlled High-Speed Gearless Elevator

Inverter control was an essential condition for achieving smooth riding comfort in high-speed AC motor-driven elevators.

World's First Inverter-Controlled High-Speed Gearless Elevator

Toshiba started manufacturing and selling elevators in 1966 and installed its first low- to medium-speed elevator at Kawai Musical Instruments Mfg.'s Maebashi facility the following year. In 1970, the company built its first Ward Leonard control-type high-speed elevator for the Toranomon 17 Mori Building. The elevator used a DC motor in its hoist. This type of high-speed elevator required advanced technologies in its construction. Vibration of the elevator during the ride had to be reduced as much as possible to maintain comfort while moving at high speed. It also had to stop accurately at each designated floor. These requirements were satisfied by using Ward Leonard control. Each DC motor was provided with a DC generator driven by a 3-phase induction motor, and the hoist was controlled by varying the voltage applied to the DC motor. However, Ward Leonard control was expensive and a great deal of space was required for installation.

In order to solve these problems and achieve both comfort and silence during operation, Toshiba developed a gearlessdrive hoisting motor without a reduction gear. This motor employed the static Ward Leonard control method, which utilized a thyristor for power conversion. The first static Ward Leonard control high-speed gearless elevator was built at the Daiichi Seimei Building in Shinjuku, Tokyo, in 1980, and an ultrahigh-speed gearless elevator was installed at the Toshiba Building in Tokyo's Shibaura district in 1984.

However, the static Ward Leonard method, which controlled the DC motors, caused power distortion and required a large power-supply capacity to improve the power factor. To overcome these shortcomings, Toshiba introduced vector-control technology and inverter technology, which had been rapidly developed in response to the need to save energy, in order to control AC induction motors with more accurate position control. The company employed a baskettype induction motor for the traction machine, and completed the world's first inverter-controlled high-speed gearless elevator in 1983, with the inverter performing variable-voltage/variable-frequency control.

While the elevator was traveling at full speed, the induction motor rotated at only a few revolutions per second, so a brushless resolver was employed to accurately detect motor rotation. Slip frequency control-type vector control was combined with inverter control, and the company was able to stabilize torque control (including stop control) and establish a method to freely control drive speed from ultraslow to full speed. In 1985, Toshiba installed its first inverter-controlled high-speed elevator at the research laboratory of Toho Gas Co., Ltd. in Aichi Prefecture.

The company continued research on thyristors for use in inverter control and dramatically enhanced their switching capacity. This resulted in the development of insulated gate bipolar transistors (IGBTs) at the end of the 1980s. The IGBT realized increased switching frequency and reduced magnetic noise in the motor, which eliminated the need for a filter circuit and resulted in a more compact system. The IGBT also allowed the development of a small, highly integrated and highly sophisticated all-digital control device, consisting of the combination of a high-speed processor, specially customized gate arrays, and a circuit capable of controlling large currents of several kHz. Today, the inverter-controlled gearless drive system is applied in high-speed elevators worldwide.

First ACGL (inverter-controlled high-speed elevator) Technical Research Institute, Toho Gas Co., Ltd. (Tokai City, Aichi Prefecture), March 1985

First ACGL (inverter-controlled high-speed elevator)
Technical Research Institute, Toho Gas Co., Ltd. (Tokai City, Aichi Prefecture), March 1985

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