Compared with ordinary transformer, amorphous alloy transformer has very excellent magnetic conductivity. The demagnetization and magnetization process is easy to complete, which is conducive to reduce the loss, increase the payload and improve the efficiency. Compared with the no-load loss of silicon steel core transformer, the no-load loss of amorphous alloy transformer is reduced by 80%, and the operation process can save energy by 25% - 50%.
1、 Amorphous dry transformer opens up a new way of metro system application
The subway is a big power consumer in the city. The daily power consumption (active power) of a 20km long subway can reach 150000 ~ 200000 kW · H. Electricity charge accounts for 30% ~ 48% of the subway operation cost, which is one of the main costs of subway operation. Because the power consumption of environmental control, lighting, escalator, water supply and drainage, weak current system and other power consumption accounts for 50% ~ 70% of the total power consumption of subway, the energy saving and consumption reduction of power consumption plays an important role in reducing the total power consumption. The no-load loss of distribution transformer is one of the important losses in power distribution network. Therefore, reducing the no-load loss of distribution transformer is of great significance to reduce the operation cost of subway.
Due to the characteristics of subway operation, the distribution transformer in the subway operates at low load rate for a long time, and the problem of no-load loss is more prominent. At present, scb10 series dry transformer is widely used in domestic metro to supply power to electromechanical equipment in station, and its no-load loss accounts for about 0.4% of its maximum power supply load.
After the conventional dry-type transformer with silicon steel core developed from scb7 series to scb10 series, it is more and more difficult to reduce no-load loss. For example, the latest scb12 series dry-type transformer has about 20% lower no-load loss than scb10 series transformer, but its price is about 20% higher than that of scb10 transformer due to the difficulty of production process and the improvement of materials. It is very difficult to reduce the no-load loss of conventional silicon steel sheet transformer on the current technical level, which is very difficult, high manufacturing cost and uneconomical. The appearance of amorphous alloy transformer opens up a new way to improve the level of energy saving and consumption reduction of distribution transformer. Compared with SC10 series transformer, amorphous alloy dry-type transformer can reduce the loss by 70%, while the current price is only 1.3-1.5 times.
2、 Economic analysis of amorphous dry transformation
The no-load loss of transformer is mainly composed of eddy current loss and hysteresis loss of iron core. Eddy current loss is directly proportional to the thickness of core material, inversely proportional to resistivity, and hysteresis loss is directly proportional to the area enveloped by hysteresis loop. The thickness of amorphous alloy strip is only 0.025mm, which is about 1 / 11 of that of ordinary cold-rolled silicon steel sheet, and its resistivity is 3-5 times of that of cold-rolled silicon steel sheet. Therefore, the eddy current loss of core made of amorphous alloy strip is much smaller than that of cold-rolled silicon steel sheet. In addition, the coercivity of the amorphous alloy is less than 4A / m, which is about 1 / 7 of the cold-rolled silicon steel sheet. The area of the hysteresis loop of the amorphous alloy is much smaller than that of the cold-rolled silicon steel sheet, so the hysteresis loss of the amorphous alloy is much smaller than that of the cold-rolled silicon steel sheet.
The working flux density of amorphous alloy material is usually about 1.3t, which is lower than 1.6 ~ 1.7t of cold-rolled silicon steel sheet, so the amorphous alloy core material is more. At the same time, because the filling coefficient of amorphous alloy strip is low, the core cross-section is increased, and the magnetostriction of amorphous alloy material is large, which makes the transformer noise increase. It is one of the difficulties and key technologies in the design and manufacture of amorphous alloy core and transformer to reasonably grasp the relationship among flux density, strip amount and noise.
Taking the industrial power consumption of about 1 yuan / kW · h, taking the 1000KVA transformer in the above table as an example, compared with scb10 transformer, amorphous alloy dry-type transformer can reduce no-load loss cost for one year, which is energy-saving electricity charge = 1 * [(1770-550) / 1000] * 24 * 365 = 10687.2 yuan. According to the transformer life of 30 years, 320616 yuan of electricity can be saved.
Taking an 18.5km long subway line in Guangzhou as an example, on March 2, 2015, its power consumption reached 155320kw · h, and the no-load loss of its power transformer was calculated as 0.4% of the total electricity. If amorphous alloy transformer is used, the energy-saving no-load loss can reach at least 0.28%, which is 435kw · h, 158737kw · h can be saved a year, and the energy-saving electricity fee is 159000 yuan. The economic benefits are obvious, which can be converted into 63.5t standard coal consumption The emission of carbon dioxide is 158.3t, which has good environmental benefits.
3、 Application of amorphous dry transformation in Metro
Amorphous dry transformer not only has excellent energy-saving advantages, but also has good electrical and mechanical characteristics. The transformer is easy to maintain and has a long life, which is widely used in many occasions. However, due to some special features, in the past a long period of time, affected its promotion in the industry. This paper analyzes the main problems concerned by subway users for a long time.
(1) Size and mass. There is a certain margin in the architectural design of subway engineering, and the increase of the size and weight of the amorphous dry transformer is relatively small, which has almost no impact on the architectural design. With the continuous progress of technology, the size and weight of amorphous dry change have been greatly reduced.
(2) Noise problems. At present, many domestic manufacturers have greatly reduced the product noise through structural improvement and shock absorption measures. The noise is slightly higher than or even close to the ordinary silicon steel transformer, which meets the requirements of the subway within the allowable range of the standard.
(3) Short circuit resistance. Through the improvement of coil design and process, the anti short circuit ability of products produced by many manufacturers has been greatly improved. In recent years, more than 100000 amorphous dry transformers have been put into operation in China, and the performance has been tested under actual working conditions.
(4) Capacity issues. At present, the single capacity of domestic amorphous dry transformer has been able to meet the needs of metro power distribution.
(5) Installation, operation, maintenance and service life. The material and process of other parts of amorphous dry transformer are basically the same as that of ordinary transformer except that the core and silicon steel dry transformer are different. It is fully suitable for metro environment and will not bring extra concerns to users.
4、 China's subway construction on the fast track
According to incomplete data statistics, in 2017, there were more than 20 cities in China, such as Beijing, Guangzhou, Shenzhen, Foshan, Zhongshan, Nanjing, Hangzhou, Luoyang, Nantong, Wuxi, Wuhu, Shaoxing and other cities. More than 50 metro lines will be built, with a total mileage of about 1400 km and a total investment of nearly trillion yuan. Amorphous dry transformer is a feasible and good choice for current Metro distribution transformer.
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