Our company is a manufacturer that specializes in manufacturing transformers and insulating materials. At present, the company mainly manufactures dry transformers and rectifying phase-shifting transformers in transformers. Why is this?
The main reason is that the dry-type transformer not only has no trouble of oil pollution, but also has the advantages of heat-resistant flame-retardant, moisture-proof and corrosion-proof. At present, there are two mainstream dry-type transformers, namely resin cast dry-type transformers and impregnated dry-type transformers. As a class h insulated dry rectification transformer, class C insulating material nomex paper is used as the insulating medium, which has higher reliability and environmental protection characteristics, and has better economy. The dynamometer system is widely welcomed.
Let’s discuss the formation and working principle of the rectifier phase-shifting transformer.
Dry-type phase-shifting rectifier transformer is a device specially designed for multi-phase rectifier power supply for medium and high-voltage inverters. It adopts Yanbian triangle phase-shifting principle and adopts a plurality of different phase-shifting angle secondary windings to form an equivalent phase number of 9 Phase 12, 12-phase, 15-phase, 18-phase, 24-phase, and 27 equal-rectifier transformers. The primary side of the transformer is directly connected to the high-voltage grid. The French car must carry an alcohol tester with multiple three-phase windings on the secondary side. It represents the Yanbian delta-connected transformers at 0°, θ°,…, (60-θ)°. Each low-voltage three-phase winding on the secondary side simultaneously represents the phase shift angle of the voltage of each low-voltage three-phase winding relative to the corresponding winding. When each phase is connected in series by an n-motor test h-bridge unit, θ=60°/n, multiplexing of inputs is achieved, and 6n pulse wave rectification is formed. In this way, if each h-bridge unit has power balance and the current amplitudes are the same, theoretically, the primary-side input current does not contain all harmonics below 6n±1, and the power factor can be improved. Generally, no reactive power compensation and harmonics are required. Filter device. It is most suitable for use in environments where fire protection requirements are high and load fluctuations are large, such as offshore oil platforms, thermal power plants, waterworks, metallurgy and chemical industry, mining building materials and other special working environments.
The multi-winding dry phase-shift rectifier transformer is designed according to different users. The capacity varies from 200kva to 10000kva, the primary impedance is large, the efficiency of the transformer is >98%, the h-class insulation system is adopted, and the temperature rise limit of the winding is 120k. In order to improve the power quality, the output waveform of the rectifier transformer is not like the power transformer has only three sinusoidal pulse waves in one cycle, but according to the primary side voltage and the installed capacity, the pulse wave number of each transformer in one cycle is determined. High-voltage variable-frequency speed control technology is currently diversified. Siemens technology represented by cascaded multiplexing technology can basically achieve perfect harmonics. It uses a rectifier transformer to superimpose (series) multiple low-voltage modules to form a high-voltage output. Power devices use igbt, the current domestic high-voltage inverter manufacturers are using this technology. Abb’s acs5000 series inverter is a three-level topology. There are 6 phase-shifted rectifiers for 36-pulse rectifier transformers. Each of the two phase-shifting groups provides power for one frequency conversion unit. The power devices are igct, abb and one frequency conversion. The device adopts 12-pulse rectification and inverter technology, and its transformer adopts three-winding form. An 18-pulse rectification inverter technology represented by ab (rockwell) requires a three-split form of a rectifier transformer.
Rectifier transformers, as an important component of this technology, have emerged and developed rapidly with the technology of high-voltage inverters. According to the number of inverter units and voltage levels, the number of output windings and voltages of phase-shift rectifier transformers is also different, 3 kv is mostly used in 3 levels, phase shift is divided into 0°, ±20°, and the voltage of each phase shift group is 630v; 6kv The use of more than six, phase shift is divided into ± 5 °, ± 15 °, ± 25 °, each phase shift voltage is 630v, there are also used five or seven, 5 when the phase angle is 0 °, ± 12 °, ±24°, voltage is 710v, phase shift angle is 0°, ±8.57°, ±17.14°, ±25.71°, voltage is 490v at level 7; 8k is used at 10kv and phase shift is ± 3.75° , ±11.25°, ±18.75°, ±26.25°, each phase shift voltage is 720v, there are also 9 and 10 levels. In theory, the more stages, the less harmonics on the input side of the transformer, the less pollution to the grid, but the number of stages, the inverter power unit is more, increasing the manufacturing cost, so the above series is the frequency conversion Manufacturers commonly used. The abb’s acs5000 frequency changer needs the transformer to be simplified with the above-mentioned some simplification; The 12 pulse wave and the 18 pulse wave rectifier transformers mostly use the splitting way, is suitable for the abb and the ab frequency changer. It is used to improve the influence of higher harmonics of rectifier devices on power grids and communications equipment.
On the basis of the three-phase voltage of the power grid, in order to obtain a uniform distribution of the secondary voltage of the multi-pulse wave, it is required that the voltage of the secondary side of each phase be evenly distributed within 120°. For this purpose, the two wiring groups y, d11 and yd1 are used to achieve mutual phase shifts of 60°. Then use the secondary side extension triangle phase shift to get the required phase angle. According to the definition of the wiring group, clockwise phase shift (+) and counterclockwise phase shift (-). For example: 18 pulses of phase-shifting transformers at intervals of 360°/18=20°. The phase shift angles of the wiring groups are: y, d11-20°; y, d11; y, d11+20°.
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