New Development of Transformers in China

In recent years, the prices of core materials and conductive materials for electronic transformers in power supply have been rising continuously, and the upstream raw materials have formed the seller's market. As power users of downstream electronic transformers, they can choose and purchase all over the world to form a buyer's market. In the middle position of the electronic transformer industry, only by taking the road of technological innovation, can we get rid of the dilemma of gas at both ends. However, in the mature electronic transformer industry, technological innovation is more difficult. But every small step of improvement can bring new ideas and new products.

To take the road of technological innovation, we must always remember the purpose we want to achieve. The electronic transformer in the power supply, like all products as commodities, carries on any technological innovation, must complete the specific function under the specific use condition, pursues the best performance-price ratio. Nowadays, power supply products are generally characterized by "light, thin, short and small" and are developing toward miniaturization and portability. The electronic transformer must be adapted to the requirements of the volume and weight of the power supply products as users. At the same time, the price of raw materials (core materials and conductive materials) for electronic transformers has risen. Therefore, how to reduce the volume and weight, how to reduce the cost, has become the main direction of the development of electronic transformers in recent years.

Silicon steel is the core material widely used in electronic transformer in power frequency power supply. In order to reduce the amount of core used in electronic transformer, it is necessary to increase the working flux density (working flux density) of silicon steel. The working magnetic density of silicon steel depends not only on saturated magnetic flux density, but also on loss. Because efficiency is an important performance index of electronic transformer, now, in order to save energy, many power products have put forward standby loss requirements. Core loss of electronic transformer is the main component of standby loss. Therefore, strict requirements are put forward for the efficiency or loss of electronic transformer.

Polymer soft magnetic composites have developed rapidly in recent years. High frequency power transformers and inductors have been manufactured with this material abroad, and corresponding analysis theory and design procedures have been established. As far as the author knows, although the research and development of polymer soft magnetic materials have been carried out in China, there is no report on the use of electronic transformers in power supply.

At present, various kinds of aluminium conductors for electronic transformers in power supply are being developed in China. Some enterprises have developed copper-clad aluminium conductors, which occupy 15% of the area and the total proportion is 3.63 g/cm3. Considering the surface effect and proximity effect, the resistivity of copper-clad aluminium conductors is much smaller than that of pure aluminium wires, and the cost increase is not much. It is a composite material that can give full play to the effect of copper and aluminium.

In recent years, another noticeable development trend is to select 180 polyesterimide QZY enameled wire with high temperature index and high heat-resistant grade and 220 polyimide QYZ enameled wire. The allowable current density of the wire increases, the diameter of the wire decreases, the amount of copper used decreases, the area of the core window decreases, and the amount of iron used decreases at the same time, which can reduce the overall cost.  Especially for high frequency and small power transformers requiring small size, enameled wires with better heat resistance can show better technical and economic benefits.

The AC voltage conversion technology included in power supply technology and power electronics technology is a kind of "pure" electronic transformer. It can also convert low voltage into high voltage for boost conversion or low voltage for step-down conversion. The main method is to use power electronics technology to increase the frequency of power conversion, so as to reduce the volume of transformers and inductors in the circuit. Eliminate transformers and inductors. Previously, this method of combining power electronic circuit and electronic transformer has not attracted enough attention. In recent years, with the increasing demand of power system to reduce input and output harmonics, improve power factor of network side, and realize "green transformation", the research of "power electronic transformer" has been carried out at home and abroad, and the upsurge of research and development has arisen. This paper studies how to use power electronic technology to transform and control power, and how to use power electronic transformer to replace the traditional electromagnetic distribution transformer. Now there are many kinds of circuit forms, such as single-phase conversion and three-phase conversion. This power electronic transformer can be used not only in the field of high-voltage and high-current power, but also in the field of high-voltage or low-voltage and low-current, such as some high-voltage power generators and small-power voltage regulators.

Our country has more than 2000 research, development and production units of electronic transformers, including state-owned, private and foreign-funded enterprises. The world's largest manufacturer of electronic transformers, Puth Corporation of the United States and TDK Corporation of Japan, the world's largest soft magnetic ferrite manufacturer, have production bases in China. Many advanced electronic transformer technologies, production processes and products in the world are gathered together in China. Faced with such a diversified platform, technological exchanges are promising.