Hello everyone, today I will share with you the knowledge about power transformers. So before, I shared the relevant knowledge about balun transformers, so what is the difference between the two, please see the introduction below.

  

Power transformer is a kind of static electrical equipment, which is used to change the AC voltage (current) of a certain value into another voltage (current) with the same frequency or several different values. When the primary winding is connected with AC, alternating magnetic flux is generated. The alternating magnetic flux induces AC electromotive force in the secondary winding through the magnetic conduction of the iron core. The secondary induced electromotive force is related to the number of turns of the primary and secondary windings, that is, the voltage is directly proportional to the number of turns. The main function is to transmit electric energy. Therefore, the rated capacity is its main parameter. Rated capacity is a customary value of power, which represents the size of transmitted electric energy, expressed in KVA or MVA. When the rated voltage is applied to the transformer, it is used to determine the rated current that does not exceed the temperature rise limit under specified conditions. The more energy-saving power transformer is the amorphous alloy core distribution transformer. Its biggest advantage is that the no-load loss value is very low. Whether the no-load loss can be ensured is the core issue to be considered in the whole design process. When arranging the product structure, in addition to considering that the amorphous alloy core itself is not affected by external forces, the characteristic parameters of amorphous alloy must be accurately and reasonably selected in the calculation.

 

Function of power transformer

 

Power transformer is one of the main equipment in power plant and substation. The function of transformer is multifaceted. It can not only raise the voltage and send the electric energy to the power consumption area, but also reduce the voltage to the use voltage at all levels to meet the needs of power consumption. In short, the step-up and step-down must be completed by the transformer. In the process of transmitting electric energy in the power system, there will be two parts of loss: voltage and power. When transmitting the same power, the voltage loss is inversely proportional to the voltage, and the power loss is inversely proportional to the square of the voltage. The transformer is used to increase the voltage and reduce the power transmission loss.

 

The transformer is composed of two or more coil windings wound on the same iron core. The windings are connected through alternating magnetic field and work according to the principle of electromagnetic induction. The installation position of transformer shall be convenient for operation, maintenance and transportation, and a safe and reliable place shall be selected. When using the transformer, the rated capacity of the transformer must be reasonably selected. When the transformer operates without load, it needs large reactive power. These reactive power shall be supplied by the power supply system. If the capacity of the transformer is too large, it will not only increase the initial investment, but also make the transformer operate under no-load or light load for a long time, increase the proportion of no-load loss, reduce the power factor and increase the network loss. Such operation is neither economical nor reasonable. The selection of transformer capacity is too small, which will overload the transformer for a long time and easily damage the equipment. Therefore, the rated capacity of the transformer should be selected according to the needs of the power load, and should not be too large or too small.

 

Development history

 

According to the data of the National Bureau of statistics, from 2007 to 2011, the sales scale of the power transformer manufacturing industry continued to expand, and the sales revenue increased by more than 13% every year. In 2011, the sales revenue reached 178.436 billion yuan, a year-on-year increase of 16.53%; The total profit was 10.214 billion yuan, a year-on-year decrease of 5.43%. Overall, in 2011, China's power transformer manufacturing industry developed stably, but its profitability declined. Considering the global economic environment, China may increase the proportion of renewable energy in the future. Both state grid and South grid are studying light DC, which are new trends and will bring new development fields to the transformer industry. Moreover, the development and use of power transformers are becoming more and more extensive in the market, and some well-known enterprises also stand out in terms of technology and quality. For example, Yikai Investment Group has been committed to the development of national electrical industry for many years, established close cooperation with many scientific research institutes, universities and international industry giants, and established "Shanghai Yikai Electric Appliance Science Research Institute" to professionally develop and produce transmission and distribution control equipment High and low voltage electrical components, intelligent electrical and other products, and successively developed various high and low voltage electrical components such as "intelligent PLC control general screen" and "intelligent complete switch general control"; In cooperation with Shenyang Transformer Research Institute, we have developed and produced high and low voltage transformer products. We have successively developed s (b) H15-M and S (b) h16-m amorphous alloy coil core power transformers, SC9, scb9, SC10 and scb10 series resin insulated dry-type transformers, SG10 class H insulated dry-type power transformers, sgb11-r class H non encapsulated coil dry-type power transformers, 10kV class S9 and S11 series oil immersed power transformers, 35kV S9 - □ - □ series oil immersed power transformers and other series products, and at the same time, developed and produced foil winding machines, amorphous alloy shears, high and low voltage winding machines and other special mechanical equipment for transformer production; Together with General Electric Company (GE), we have built the largest and most professional marine switchgear and low-voltage electrical equipment in the Asia Pacific region, and successively developed GEA plus2 0. Modula plus, modula 630k, marine transformer, marine box type substation, marine electrical automation equipment, tunnel special distribution cabinet and other products.

 

In 2009, Shenzhen aodian High Voltage Electric Co., Ltd. (hereinafter referred to as "aodian high voltage") developed the world's first 110kV evaporative cooling power transformer and put it into power grid operation in 2013.

 

In February 2018, the design scheme of 220kV / 120000kva evaporative cooling power transformer developed by aodian high voltage passed the expert review of China Machinery Industry Federation, and in July, the world's first 220kV evaporative cooling power transformer was successfully trial produced. This power transformer uses a new type of low boiling point, non combustible and environment-friendly liquid insulation material as the insulation and cooling medium of the transformer, and efficiently cools the transformer according to its own gas-liquid phase change, so that the substation can be "indoor, miniaturized and oil-free", which will be cleverly embedded in the Office area, production area and living area, release land resources and do not occupy urban space alone.

 

Development prospect

 

1. Medium frequency transformer has large output and low price, and is mainly exported, which drives its rapid development. At present, the industry average price of medium frequency transformers in China's electronic system enterprises is 0.626 yuan / piece, but the average ex factory price of most enterprises is between 0.20 and 0.30 yuan / piece, and the higher one is about 1 yuan / piece.

 

2. There is a strong market demand for power transformers. Power transformer is a labor-intensive product, which is mainly customized by users. In recent years, there has been strong market demand at home and abroad, and it has become a hot product with rapid development. India will grow by 25%. Communication, computer and consumer electronic products are its three main markets, among which the growth of communication demand will play a great role. At present, the annual demand of global power transformer has exceeded US $10 billion, and is developing to surface installation, high power and high voltage.

 

If the amorphous alloy transformer can completely replace the new S9 series distribution transformer, for example, when the annual demand of 10kV distribution transformer is calculated as 50 million KVA, it can save 10 billion kw a year? H above. At the same time, it can also bring good environmental protection benefits of less power plants and less greenhouse gas emissions to the atmosphere, which will greatly reduce the direct pollution to the environment and make it a new generation of green environmental protection products worthy of the name. In short, in the development and transformation of urban and rural power network system, if the country can widely promote the use of three-phase amorphous iron core distribution transformer products, it will eventually obtain the benefits of energy conservation and environmental protection.

 

Classification of power transformers

 

Power transformers are classified by purpose: step-up (power plant 6.3kv/10.5kv or 10.5kv/110kv, etc.), liaison (220kV / 110kV or 110kV / 10.5kv between substations), step-down (35kV / 0.4kV or 10.5kv/0.4kv for power distribution).

 

Power transformers are classified according to the number of phases: single-phase and three-phase.

 

Power transformers are classified according to windings: double windings (each phase is installed on the same core, and the primary and secondary windings are wound separately and insulated from each other), three windings (each phase has three windings, and the primary and secondary windings are wound separately and insulated from each other), autotransformer (the middle tap of a set of windings is used as primary or secondary output). Three winding transformer requires the capacity of the primary winding to be greater than or equal to the capacity of the secondary and tertiary windings. The percentage of three winding capacity is in the order of high voltage, medium voltage and low voltage: 100 / 100 / 100, 100 / 50 / 100 and 100 / 100 / 50. It is required that the secondary and tertiary windings cannot operate at full load. Generally, the voltage of the tertiary winding is low, which is mostly used for near area power supply or compensation equipment to connect three voltage levels. Autotransformer: there are two kinds of step-up or step-down transformers. Because of its small loss, light weight and economical use, it is widely used in EHV power grid. The commonly used model of small autotransformer is 400V / 36V (24V), which is used for power supply of safety lighting and other equipment.

 

Power transformers are classified by insulation medium: oil immersed transformer (flame retardant and non flame retardant), dry-type transformer and 110kvsf6 gas insulated transformer.

 

The cores of power transformers are of core structure.

 

The three-phase power transformer configured in general communication engineering is a double winding transformer.

 

Well, the above is the relevant introduction of power transformer. If you have any questions, please leave a message at any time. If you want to know more, please pay attention to us and see you next time.