The predecessor of Shaanxi Haili Electric Engineering Company Limited (former “Xi’an Power Rectifier Works”) was Xi’an High Voltage Switchgear Rectifier Works built with assistance from the Soviet Union during the “First Five-year Plan”. It started producing mercury rectifiers in 1958. It produced mercury rectifiers of 100,000 to 150,000 kW in 1960s and acted as the main production base of DC power source devices used for electrochemical and metallurgical industries. It then became the national scientific research and production base of rectifiers and that speeded up the development of silicon rectifiers for electrochemical and metallurgical industries. In 2001, it carried out institutional restructuring and established Shaanxi Haili Electric Engineering Company Limited (“Haili Company” for short). For over thirty years, it has been the leading company in manufacturing silicon rectifiers for electrochemical and metallurgical industries, and it holds a leading position in China in terms of production and technology. It has developed over 200 kinds, more than 1000 specifications of air-cooled and water-cooled rectifiers with series GHF, GHS, GES, KGHS, GHSa-W (outdoor type), ZHS, KHS, etc. It has provided nationwide aluminum magnesium metal electrolysis plants, chemical industry, electrical carbon and other enterprises with about 9 million kW silicon rectifiers, which accounts for 60% of the total output in China over the years.

    In 1964, it successfully developed the first silicon rectifier in China for water electrolysis application.

     In 1963, 10A diode was successful in trial production; in 1964, GHF-750/245 silicon rectifier for water electrolysis application and 200A diode for 750A, 245V were successfully developed. Meanwhile, the first batch of fast fuses of 750V, 320A with breaking capacity of 50kA was successfully developed. It had laid a solid foundation for the development of silicon rectifiers in China.

    In 1967, GHF-22000/700 rectifier (22000A, 700V) for Lanzhou Liancheng Aluminum Plant was successful in trial production, which initiated a new epoch of China high power silicon rectifiers for electrolysis application. In the same year, the double holes water-cooled copper busbar was successfully developed jointly with Yellow River Smelting Plant. By using this kind of busbars as an electric conductor, the first batch of GHS-2000/300, 25000/120 water-cooled silicon rectifiers in China was successfully trial-produced. Year by year, it has developed various kinds of water-cooled products for electrolysis application with series 3000A, 6000A, 12000A, 25000A and voltage range from 36V to 800V. This type of products with advanced structure is only half size of that air-cooled type. With the advantages of low noise, high efficiency and convenient maintenance, these products were favorably received by domestic metallurgical and chemical industries, and had exported to Albania and other countries. In the meantime, they were used for replacing the old mercury rectifiers.

    In 1970s, the technology and variety of silicon rectifiers went up to a new level.

    In 1970s, XD Power Rectifier Works actively developed thyristor rectifiers for electrolysis application. In 1975, KGHS-6000/600 thyristor rectifier was produced. It was water-cooled type, consisting of 500A thyristors and with current regulation of 1%. Year by year, it has formed the series products of 750A, 1500A, 3000A, 6000A, 12000A with voltage range from 36V to 600V, which made chemical electrolysis power supplies on a new step.

    In 1979, the first China outdoor 63kA, 315V 20MMW transformer rectifier was successfully trial-produced with joint efforts from Xi’an Transformer Furnace Plant, which filled up the gap of this technology in China and won the third prize of technology progress awarded by Ministry of Machine Building Industry. The product has been running in Shanghai Tianyuan Chemical Plant. Each year less than 0.1% of the damage rate of diodes has shown the high reliability of this product.

    Cophase anti-parallel ZHS series silicon rectifiers and KHS series thyristor rectifiers are the second generation of DC power supply in China for electrolysis application

    In 1983, ZHS1-30-63kA and ZHS2-15-31.5kA series cophase anti-parallel high capacity rectifiers were developed by absorbing the advantages of the silicon rectifier that introduced by Guizhou Aluminum Plant from Japan Fuji Electric Machine Company for aluminum electrolysis and combining with experience. A prototype of ZHS-50kA/700 (50kA, 700V) was delivered to Baotou Aluminum Plant in May, 1985. This product adopted 1000A (or 1600A) diodes and 1400A fast fuses imported from Japan. The prototype is backside closed and the side door opened from both sides. There was a service corridor in the cubicle. This structure made it possible to install the transformer and the rectifier next to each other to shorten the connecting busbar and to connect directly at the place of top 1/4 of rectifier arm busbar. It improved the magnetic field distribution along the rectifier arm and helped to better the current balance between the diodes to reduce the reactance voltage drop and connection loss of the leading wire, so as to improve the efficiency of the rectifier cabinet. The distance between two rectifier arm conductors was reduced to the minimum, so the external alternating flux between electric conductors was almost entirely offset. In this way, the problems of eddy-current loss and frame overheating caused by heavy current magnetic field have been solved basically. The temperature rise in ZHS series rectifier cubicles has dropped sharply comparing with GHS series rectifiers. In terms of control circuit, the new saturable reactor automatic constant current system controlled by thyristor solid circuit was developed, and it can realize the power supply constant current control for multiple units in parallel connection. The successful operation of ZHS-50kA/200kV four units in parallel (Baotou Aluminum Plant) marked that Haili Company had reached the international level in early- and medium-term of 1980s in terms of rectifier technology. In 1986, adopting the structure of ZHS series and thyristors of 1000A-1600A, Haili Company successfully developed high power cophase anti-parallel KHS series thyristor rectifiers for electrolysis application, the current rating from 15000A to 100000A. That accomplished the updating of the second generation of products.

    Since 1985, the summed current that ZHS series and KHS series products provided to the market has been over 1.5 million kA. Such as the metallurgical enterprises like Baotou Aluminum Plant, Liancheng Aluminum Plant, Lanzhou Aluminum Plant, Urumqi Aluminum Plant, Qinghai Aluminum Plant, Qingtongxia Aluminum Plant, Huludao Zinc Plant; and the chemical enterprises like Guangzhou Chemical Plant, Quzhou Chemical Plant, Zhejiang Chemical Plant, Hubei Chemical Plant, etc.

    From 1987 to 1991, Company had co-operation successively with ASEA, SIEMENS and ALSTHOM for introduction and manufacture of the electrolytic rectifiers for domestic aluminum plants. Consequently, Company had learnt about the technical characteristics of high power electrolytic rectifiers used in Western European large-scale electrical enterprises and had absorbed their advantages.

    In 1992, Haili Company developed the third generation of rectifiers in China for electrolysis application. The 3-inch semiconductor elements (diode current 3500A-4500A, thyristor current 2000A-3000A) were used in the new generation of rectifiers. With new RSH series fast fuses and new large water-cooled busbar clamping structure of semiconductor elements, the current of single semiconductor element is increased. In this way, the number of semiconductor elements in parallel is decreased, current balance coefficient is improved, and the volume is reduced. Furthermore, it has created the conditions for simplifying the rectifier cabinet layout and for diversifying the cubicle structure.

    Starting in 2001, Haili Company made improvements on all original rectifiers. The multiple series of rectifier cubicle structures have been established, including cabinet type (totally-enclosed cabinet with protection class of IP54), frame type, electric busbar self-supporting type and totally-enclosed outdoor type, etc.

    The control circuit adopts big board structure to make the components integrated and modularized. With less plug connection points, its reliability is higher and anti-interference ability is stronger. The operational data and waveforms at each point in the control panel can be online tested and monitored. There are also various improvements in the new pulse distributor and strong trigger system, and its technical performance has improved significantly. All other electric parts are manufactured with the introduced technology or are imported products.

    By using computer aided design and optimization design, the new generation of rectifier devices for electrolysis application has higher efficiency and higher reliability. The heavy current of its single unit and the variety of its structure are unprecedented, which once again raised the high current rectifier power supply technology in China to a new level.