1 Introduction
Most of the industrial DC power supply is obtained by rectifying equipment composed of rectifier transformers and rectifiers and is widely used in the fields of metallurgy, chemical and traction, such as urban rail transit, rolling motor DC transmission, synchronization. DC excitation of the motor, etc. The role of the rectifier transformer is to convert the AC grid voltage into the voltage required to rectify the device, and improve the operational characteristics of the AC and DC side through the transformation of the phase and the phase angle. Rectifier transformers can isolate the rectifier and grid circuits to ensure the safety of the equipment, and limit the short-circuit current, reduce the electromagnetic interference between the rectified equipment to the electromagnetic interference between the grid and other parallel transport rectifiers, inhibit the current increase of the rectifier element such as thyristors.
Due to the oil-proof pollution problem, moisture-proof, heat resistance, flame retardant, anti-corrosion, etc., widely used in various aspects of industrial and life. There is currently two mainstream type dry transformers: one is a resin cast dry transformer (ORDT) represented by Europe, and the other is the immersion dry transformer represented by the United States (IVDT) . As a dry rectifier transformer with H-level insulation, Nomex paper with C-stage insulation is higher, with higher reliability and environmental protection, and has better economics, which is widely welcomed.
H-class dry rectifier transformer heat-resistant grade is 180 ° C, the main insulation material is Nomex paper, the insulation paper is a patented product of DuPont, which is a synthetic insulating material based on aromatic amide fibers, which is C-class , Heat resistance is 220 ° C. Nomex paper has many advantages. It is an excellent electrical insulating material that can moisture resistance, flame retardation, good environment, and the size of the transformer is compact, and the transformer is small, and the anti-refrigeration of transformers is resistant. The anti-overvoltage capacity is better than other types of transformers. In particular, the manufacturing process and product structure of H-level rectifier transformers are characterized for rectifier transformers that require multiple taps and structural complex plurality of phase windings, which make it shorter, low cost, low cost. The lattice of the vacuum pressure impregnation (VIP) is rigid and the mechanical strength is guaranteed. At the same time, the moisture-proof ability of the transformer is improved due to the lacquer film covers the surface of the insulating material.
2 Formation and working principle of shift phase
The dry phase rectifier transformer is a device specifically providing a multi-phase rectifier power supply for medium and high voltage inverters. It employs the principle of delayed triangles, and can form an equivalent phase of 9 through a plurality of different phase shift angle secondary windings. Phase, 12-phase, 15-phase, 18-phase, 24-phase and 27-phase rectifier. On the primary side of the transformer into the high voltage grid, there are multiple three-phase windings on the secondary side, which represents the secondary side of the secondary side of the delay triangle to connect the secondary side of the delay triangle in 0 °, θ °, ..., (60-θ) °. The winding is simultaneously shown in each low pressure three phase winding voltage relative to the corresponding windings. When each phase is connected in series by n h-bridge units, θ = 60 ° / n, the input multipart is realized to form a 6N pulse wave rectification. Thus, if each H-bridge unit power is balanced, the current amplitude is the same, theoretical in the first side input current does not contain 6N ± 1 or less harmonics, and can improve the power factor, generally no need to replenish reactive power compensation and harmonics Filtering device. It is most suitable for use in environments with high fire prevention requirements, large load fluctuations, such as special working environments such as maritime oil platforms, fire power plants, tap water plants, metallurgical chemicals, mine building materials.
Multi-winding dry phase shift rectifier is designed according to different users, with a capacity from 200kva to 10,000kVA, the primary impedance is large, the transformer is efficient. 1882.98%, using an H-level insulation system, the winding temperature rose value of 120K. In order to improve the power quality, the output waveform of the rectifier transformer is not like only three sinoid pulses in one cycle, but determines the number of pulse waves per transformer in one cycle according to the primary side voltage and the installed capacity. The high-voltage variable frequency speed speed adjustment technology is currently diverse, and the cascaded multi-rendering technology represented by Siemens technology is basically the perfect harmonic. It uses a rectifier transformer to set a plurality of low-voltage modules (series) to form high-voltage output. Power devices use IGBT, and most high-voltage inverter manufacturers in China use this technology. ABB's ACS5000 series drive is a three-level topology structure. The rectifier transformer of 36 pulse waves has 6 phase-phase groups. Each two phase shift group is powered by a variable frequency unit, and the power device is IGCT, and ABB has a variable frequency. The 12 pulse wave rectifier inverter technology is used, and the transformer uses three winding forms. 18 pulse wave rectification inversion techniques represented by AB (Rockwell), which requires a rectifier transformer in three split forms.
The rectifier transformer is an important configuration of this technology, which is developed and rapidly developed with the technology of high voltage inverters. Depending on the number of inverter units and the voltage level, the number of differential rectifier transformer output windings and the voltage are different. 3kV is 3-level, the shift phase is 0 °, ± 20 °, each shift group voltage is 630V; 6KV Multi-use 6-stage, shift phase is ± 5 °, ± 15 °, ± 25 °, each shift group voltage is 630V, and use 5 or 7 level, 5-stage shift angle is 0 °, ± 12 °, ± 24 °, voltage is 710V, 7 levels of transpillate angles 0 °, ± 8.57 °, ± 17.14 °, ± 25.71 °, voltage is 490V; 10KV multi-use 8-level, shift phase is ± 3.75 ° ± 11.25 °, ± 18.75 °, ± 26.25 °, each shift group voltage is 720V, and 9 and 10 levels are also used. In theory, the more the levels, the less harmonics on the input side of the transformer, the smaller the pollution of the grid, but the levels, the power unit of the inverter, increase the manufacturing cost, so the above level is the variable frequency The manufacturer is generally used. ABB's ACS5000 inverter desired transformers need to simplify some of them; 12 pulse and 18 pulse rectifier multi-splitting mode, suitable for ABB and AB inverters. It is used to improve the impact of high harmonics of rectifier devices on devices such as grid and communication.
On the basis of the three-phase voltage of the grid, in order to obtain a uniform distributed multi-pulse secondary side voltage, each phase is required to be uniformly distributed in a 120 ° inner voltage. For this purpose, the two wiring groups of Y, D11 and YD1 are used to achieve 60 ° interming phase. The secondary side delay is used to obtain the required phase angle. According to the wiring group, it is (+) in clockwise phase shift phase (+) to counterclockwise (-). For example: 18 pulsed transformers, interval: 360 ° / 18 = 20 °. Its wiring group is adjacent to: Y, D11-20 °; Y, D11; Y, D11 + 20 ° in sequences, respectively. Technology area
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