There has been an expanding demand for uninterruptible power systems (UPS) with the progress of information networks. Fuji Electric has developed UPS business under the motto of "creating a more reliable UPS with customers", resulting in their appreciation and its reputation. The company, utilizing up-to-date technologies of semiconductors, control systems, quality assurance, etc., offers a satisfactory line-up of products meeting various market needs. The paper also introduces technical seeds to suit market needs such as free installation, load coordination, reliability and maintainability, harmonic current suppression, improved systems, and others.

In high-grade information network societies a large-scale uninterruptible power system (UPS) plays an important part to supply high-quality electric power to widely used computer systems particularly for urban banks. Reliability is a first priority in such a system; power supply shall be stable without any interruption 24 hours a day all year round. This paper describes technical items of special importance to make up a reliable large-scale UPS citing several examples of our actual installations resulting from Fuji's abundant know-how.

High-frequency switching technology was applied only to small-capacity uninterruptible power systems (UPS) these few years. With improvement in the performance and current capacity of power semiconductors, especially of high-speed switching elements such as MOSFETs and IGBTs, the application has extended to large UPSs.
Fuji Electric has put on the market a new series of 75 to 200 kVA output, 3-phase UPSs using IGBTs as switching elements. This paper introduces its specifications, features, circuit configuration, panel construction and test results.

Uninterruptible power systems (UPS) have been employed to supply stable electric power to computers introduced in various ways as the information-oriented society advanced.
This paper introduces the features, standard specifications, and circuit configurations of Fuji Electric's new medium UPSs with MOSFETs in the main circuit. The UPS can be installed right beside a load in a computer room or an office because it is small, light, and quiet.

Demand for the mini-uninterruptible power system (Mini-UPS) has rapidly increased as small computer-applied equipment came into wide use. The UPS of this kind is required improvement in input characteristics in addition to high-performance output characteristics.
To meet these needs, Fuji Electric has developed a small high-performance Mini-UPS having high-quality input current including little harmonic components as well as excellent output characteristics by combining a high-frequency switch-mode rectifier circuit and a high-frequency PWM inverter circuit. This paper introduces its specification, features, circuit configuration and characteristics

Computers continue to spread in every corner in information-intensive times. The uninterruptible power systems (UPS) for computers require particularly high reliability and long-term maintenance of high-quality.
Fuji Electric has developed a UPS monitor for this purpose. The monitor, using an industrial microstation L25, has realized high-grade maintenance, complete preventive maintenance, and quick restoration.

The building constructed as an on-line computer center is in operation 24 hours a day all year round. This paper describes the configurations and functions of the uninterruptible power system and substation switchgear system supporting the computer system under such an operating condition by an example of the actual installation. The paper also outlines the related cogeneration system and central monitor system.

Fuji Electric has newly developed a 400-Hz airport power supply system of a static type with power transistors. Its features are not only high efficiency, high reliability, and easy maintenance but also cable drop compensation, protection against instantaneous input failure, and a 12-pulse rectification against harmonic current input.
The company also developed another 400-Hz power supply system with DC input which has a rectifier at one place and a number of distributed DC-input 400-Hz inverters.

Computer application has recently advanced rapidly, so that instrumentation power supply systems are required strongly to reduce the distortion of output voltage, to cut down the acoustic noise, and to be reduced in size and weight. To meet these requirements, Fuji Electric has developed a new-type high-performance CVCF inverter for instrumentation use with MOSFET modules incorporated.
This paper introduces its features, specifications, circuit configuration, and characteristics.

The uninterruptible power system (UPS) installed in office rooms, which is in rapidly increasing demand, requires improvement in size and weight, in acoustic noise, and in cost as well as in electrical performance.
Fuji Electric, to meet these needs, has continued research into high-frequency technology application to UPSs.
This paper introduces two examples of the latest UPSs manufactured for trial and tested: a high-frequency link DC-DC converter type, 3-phase, 50kVA UPS and a high-frequency link cycloconverter type, single-phase, 10kVA UPS.