Analysis On The Charater Of The Multi-Function Balance Transformer And Study On Its Application

Electrical railway traction load is the two-phase or the single-phase load with abundant harmonics. Low power factor, abundant harmonics and negative sequence are the three main characters of electrical railway traction load. It has hampered the development of the electrical railway for many years. The influence of negative sequence is almost eliminated along with the enlargement of the system's capacity and the alternate connection of traction substations. Now the appearance of the Multi-function Balance Transformer (MFBT) gives us a batter method to result these problems.The MFBT is based on the Impedance-Matching Balance Transformer (IMBT) which is designed by our country. Its two-phase system can satisfied the needs of electrical railway traction. One hand, the MFBT has merits of high utilization rate and eliminating negative sequence which inherit from the IMBT. The other hand, the new taps which voltage is 10.5kV are setted at a-phase winds and c-phase winds of the secondry winds.The secondary three-phase system of the MFBT can be used in many such purposes as providing local electricity, compensation of reactive power and reducing the amount of the harmonics caused by electrical railway traction load through seting L-C series branches at the taps.These L-C series branch make the secondary harmonic current balance in ampere-turn. So the MFBT can be satisfied the needs of quality of electrical power and criterion of voltage performance and make multi-function ture.Firstly, the functions in transforming voltage, three-phase to two-phase, compensation of reactive power and reducing the amount of the harmonics of the MFBT are analysised, three formulae of the harmonic current of the primary side are deduced,and compared with the normal method in leaching harmonics in this paper. The result of the comparation indicates ,that the total percentage to leach the 3rd, 5th and 7th harmonics current of the MFBT is 11.11% higher than the normal method in leaching harmonicsSecondary, a model of the MFBT is established through Matlab7.01 in this paper. It approves the functions in transforming voltage, three-phase to two-phase, by the MFBT model.Lastly, technical and economic benefit of the MFBT is analyzed at last of this paper. The result indicates that the MFBT is outstanding. The MFBT has bright foreground in Electrical railway.