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World's First Vector-Control Inverter

The desire to control AC motors as freely as DC motors is fulfilled by using vector operation, opening up a new era of AC variable-speed motor drives.

World's First Vector-Control Inverter

In 1979, Toshiba implemented the world's first vectorcontrol AC variable-speed motor drive, an inverter and induction motor combination designed to provide highperformance control, in a large-scale factory. The company won the “Ten Great New Products of 1979” award from the Nikkan Kogyo Shimbun (Business & Technology Daily News) in recognition of its vector-control inverter for driving large-scale paper machines.

Until then, DC motors had been utilized in variable-speed motor drives to provide high-performance control. The output of DC motors can be controlled freely according to the DC voltage level. However, these motors also have to supply power to rotating parts and therefore have a complex structure. On the other hand, AC motors (induction motors) need to power only the fixed parts. They are simple in structure and require little maintenance, but controlling the AC voltage and frequency with an inverter results in transient vibration, and it takes time to stabilize the output. A concept had been developed to control the AC vector according to the magnetic flux vector produced by the induction motor, but it was difficult to detect the magnetic flux directly and the concept failed to reach the production stage. In 1978,Toshiba announced that it had found a way to determine the AC vector during operation, solving the detection problem, and in the following year implemented a practical vector control system in a 500 kW large-capacity motor drive.

Although it had been considered too early and risky to adopt this technology in 500 kW machines, the drives were used in a paper plant and operated smoothly with the help of elaborate vector-control design and fine tuning. This opened up a new era of AC variable-speed motor drives. Toshiba deployed its microcomputer-based digital controls ahead of other companies, and its AC motor drives were installed in steel plants with capacities of more than 10,000 kW. As a result of Toshiba's innovation, Japan became the world leader in AC variable-speed motor drive technology and DC motors were rapidly replaced by AC motors.

Today, this technology has become the standard control method. Vector control is implemented not only in the industrial sector but in many other fields, forming the basis of AC motor control in various motors of differing capacities including induction motors, synchronous motors, and permanent-magnet motors.

For example, the world's first inverter air conditioner was developed by Toshiba in 1982, and the introduction of vector-control technology further reduced noise and power consumption. Toshiba also adopted vector-control technology in its elevators and developed the world's first inverter-controlled high-speed gearless elevator in 1983, which simultaneously offered both high speed and comfort. And in the railway sector, vector-control technology allowed the development of the regenerative brake, effective to zero velocity, as well as a function to quickly respond to idle running of wheels.

500kW induction motor

500kW induction motor

Steel rolling plant

Steel rolling plant

700 series Shinkansen bullet train

700 series Shinkansen bullet train

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