Variable-speed drives are now indispensable system components to electrical equipment for industrial plants. This paper outlines the present status of Fuji Electric's technology of power conversion equipment, control technology and driver networks in the industrial variable-speed drives as well as views the technical trends of variable-speed drives.

Fuji Electric has brought out IGBT inverter FRENIC4000 series, a new model based on the former common DC link converter. This paper introduces the series classified into three types by uses: (1) vector-controlled FRENIC4000VM4 for high-precision speed control and torque control, (2) FRENIC4000FM4 for constant V/f control, (3) FRENIC4000T4 for the synthetic fiber industry. The paper also describes the maintenance and inspection tool as the man-machine interface.

To meet the market needs for high performance, advanced function, easy operation, small size and wider application, Fuji Electric has developed the new vector-controlled inverter FRENIC5000VG5. Its main features are improved control performance, easy adjustment with the automatic tuning function, and general-purpose motor drive with the sensorless vector control function. The size of the drive unit is much reduced by loss reduction and improved cooling efficiency. This paper outlines the specifications and features of the new inverter.

Fuji Electric has developed neutral-point-clamped (NPC) inverters with large capacity reverse conducting GTO thyristor of 4,500V/3,000A for high-voltage, large capacity GTO PWM inverters for variable-speed drive systems. The inverter output capacity is 3,000kVA and the output voltage is 3,300V to drive high-voltage motors directly. The direct digital control (DDC) system with control-oriented programming language featuring flexible hardware and software is applied to the control system. The PWM control uses unipolar and dipolar PWM to decrease output voltage harmonics in the whole speed range.

Variable-speed drive systems have rapidly developed with the progress of power devices and their application technology. Currently, large capacity inverters use GTO thyristors. There is much demand for application of high frequency, and the practical use of power devices meeting the demand is hoped for. This paper introduces an outline of the world's first IGBT with pressed contact structure which can be one of answers to the demand, and also refers to trends of future power devices.

In regard to winding equipment for sloping shafts in mines, there is strong demands for compact, easy-to maintain drive equipment, including the machine, and suppression of a change in cage traveling speed and rolling during stopping caused by rope expansion and contraction. To meet these demands, Fuji Electric has developed, put to practical use and supplied characteristic systems. This paper introduces a typical example of the cyclocon-verter drive and H∞ control of the world's largest class permanent magnet synchronous motor which was applied to a huge sloping shaft winding machine.

Against the vibration caused by long-period disturbances such as wind and wave, large-scale structures have been designed so that the vibration should be suppressed. Recently, active methods of suppressing vibration by adding an active mass damper have been studied. They include applications of high-speed positioning systems. This paper focuses on an active mass damper applied to tall buildings, bridges, and ships as application examples of variable-speed AC drive. The outline and usage of an active mass damper, and the effect of vibration control are introduced.