Close-coupled S-Formers/Long-life diodes and thyristors

Close-coupled S-Formers

With High-unit Rating, Reliability, Long-life Expectancy and Versatility

Diode S-Formers

Close-coupled S-Formers are designed to supply the DC power requirements of a typical aluminum reduction plant, chlor-alkali plant and other electrolytic services.

The S-Formers are composed of a rectifier cubicle and a rectifier transformer. The rectifier cubicle and transformer are assembled separately and then connected (together) by short flexible bars, thus forming close-coupled S-Formers.

The rectifier is cooled by a cooling system such as WFWF (forced water, forced water), WFAF (forced water, forced air), AFAF (forced air, forced air) or AF (forced air) depending on the customer's requirement for each particular application.

The cooling system of the transformer is either OFWF (forced oil, forced water) or OFAF (forced oil, forced air).

The S-Formers are available in many different sizes up to a maximum DC output of 1500V (double-way) or 250kA (single-way)

Diode S-Former, 33kV AC/1130V DC, 55kA
Fig.2 Conceptual Arrangement of Close-coupled Diodes S-Former

Thyristor S-Formers

Thyristor S-Formers have basically the same construction as the close-coupled diode S-Formers except that thyristors are used in place of diodes. The thyristor S-Formers have become almost predominant in chlor-alkali plants and electrolytic copper refinery applications. The thyristor S-Formers do not require an on-load tap-changer (LTC) and saturable reactor, facilitating maintenance. The thyristor S-Formers are available for the same ratings as diode S-Formers.

Thyristor S-Former, 69kV AC/407V DC, 147kA

Long-life Diodes and Thyristors

Reliability of Fuji Power Semiconductors

The diodes and thyristors used in Fuji S-Formers are manufactured in our Matsumoto Factory, which is one of the largest semiconductor factories in Japan. These power semiconductors are made under carefully controlled environmental conditions, with testing and checking at each stage of manufacture, including the purchasing and procurement of materials and parts, the manufacturing process and throughout the final inspection.

Fuji Electric's diodes and thyristors have exceptionally high reliability, as proven by the extraordinary low failure rate of approximately 0.012% per year in over 30 years of operational experience.

Moreover, we're still striving to further improve this reliability level.

Voltage Ratings

Fuji Electric has been supplying diodes and thyristors rated up to 5000V (peak reverse voltage), and even higher ratings can be supplied.

Fuji Electric's diodes and thyristors are designed with an ample creepage distance between the anode and cathode, thus assuring reliable performance at various voltages.

Current Ratings

Fuji Electric's diodes and thyristors can carry as much as 3500A of continuous forward current and have a high-overload capacity.

Table 1 shows the ratings of typical diodes and thyristors used for S-Formers.

Fuji Power Diodes and Thyristors
Table 1 Ratings of Diodes and Thyristors