Data from the National Bureau of Statistics shows that from 2007 to 2011, the sales scale of the power transformer manufacturing industry continued to expand, with sales revenue growing at a rate of over 13% annually. In 2011, sales revenue reached 178.436 billion yuan, a year-on-year increase of 16.53%; total profits reached 10.214 billion yuan, a year-on-year decrease of 5.43%. Overall, in 2011, China's power transformer manufacturing industry maintained stable development, but profitability declined somewhat. Considering the global economic environment, my country may increase the proportion of renewable energy in the future. State Grid and China Southern Power Grid are both researching lightweight DC transmission systems, which represent new trends and will bring new development areas to the transformer industry. Furthermore, the development and use of power transformers in the market are becoming increasingly widespread. In terms of technology and quality, some well-known enterprises have also stood out. For example, Yikai Investment Group has been committed to the development of the national electrical industry for many years. It has established close cooperation with many research institutes, universities and international industry giants, and set up the "Shanghai Yikai Electrical Science Research Institute". It specializes in the research and development and production of power transmission and distribution control equipment, high and low voltage electrical components, intelligent electrical products and other products. It has successively developed various high and low voltage electrical components such as "intelligent PLC control panel" and "intelligent complete switch control".
In collaboration with the Shenyang Transformer Research Institute, we have developed and produced high and low voltage transformers, including the S(B)H15-M and S(B)H16-M amorphous alloy wound core power transformers, SC9, SCB9, SC10, and SCB10 series resin-insulated dry-type transformers, SG10 type H-class insulated dry-type power transformers, SGB11-R wound core H-class unencased coil dry-type power transformers, 10kV S9 and S11 series oil-immersed power transformers, and 35kV S9 series oil-immersed power transformers. We have also developed and produced specialized machinery and equipment for transformer production, such as foil winding machines, amorphous alloy shearing machines, and high and low voltage winding machines. Furthermore, in partnership with General Electric (GE), we have created the largest and most professional marine switchgear and low-voltage electrical equipment manufacturing facility in the Asia-Pacific region, developing products such as GEA plus 2.0, Modula plus, Modula 630k, marine transformers, marine prefabricated substations, marine electrical automation equipment, and tunnel-specific distribution cabinets.
We will delve into the classification of distribution transformers. Based on installation location, distribution transformers can be divided into indoor and outdoor types. Outdoor installations are further subdivided into platform-mounted, pole-mounted, and ground-mounted (including pre-installed) types. Pole-mounted installation is a unique method, involving mounting the transformer on a pole-supported structure, and is divided into single-pole and double-pole types. When the distribution transformer capacity is 30KVA and below, a single-pole distribution transformer platform is often used; while for capacities between 50KVA and 315KVA, a double-pole distribution transformer platform is more commonly used. The advantages of this installation method are smaller footprint and higher energized parts above the ground, thus reducing the risk of accidents; however, the disadvantage is that the platform uses more steel, resulting in a relatively higher cost.
When installing a platform-type transformer, it is essential to ensure that a sturdy fence or wall at least 1.8 meters high is erected around the transformer, and that a dedicated lock and personnel are assigned to manage it. For safety, a sufficient safe operating distance must be maintained between the fence/wall and the transformer, and warning signs such as "High Voltage Danger, Do Not Climb" must be prominently displayed on the pole or wall to prevent personnel and animals from approaching live parts. Furthermore, while platform-type installation is inexpensive and easy to maintain, it requires a large area and necessitates surrounding fencing, thus posing a risk that small animals may climb onto live parts; therefore, extra care must be taken to prevent damage from external forces.
A ground-mounted transformer is one that is placed directly on the ground, with its high-voltage down conductors, drop-out fuses, and surge arresters all installed on the line terminal pole. During installation, reliable barriers must be erected around the transformer, and warning signs must be posted. Because the live parts of a ground-mounted transformer are close to the ground, the power must be disconnected before entering the protected area.
In addition, transformers can also be classified according to their cooling method, mainly into oil-immersed and dry-type. Oil-immersed transformers rely on oil as the cooling medium, such as oil-immersed self-cooling, oil-immersed air cooling, oil-immersed water cooling, and forced oil circulation. Dry-type transformers, on the other hand, mainly rely on natural air convection for cooling, or use fans for forced cooling. They are mostly suitable for small-capacity transformer applications such as high-rise buildings, highway toll stations, local lighting, and electronic circuits.
Transformers can be classified in various ways, depending on the perspective. The main classifications are based on factors such as application, structure, and cooling method. Below are some common classifications and detailed explanations:
I. Classification by Use
1. Power transformers: Used for voltage transformation and power transmission in power systems, including step-up transformers, step-down transformers, and distribution transformers.
2. Special transformers: designed for specific scenarios, such as electric furnace transformers, rectifier transformers, test transformers, mining transformers, etc.
3. Instrument transformers: used for measurement and protection, such as current transformers and voltage transformers.
4. Voltage regulating transformer: Voltage regulation is achieved by adjusting the winding turns ratio. It is divided into two types: no-load voltage regulating and on-load voltage regulating.
II. Classification by number of phases
1. Single-phase transformer: Suitable for single-phase AC circuits, commonly found in households and small equipment.
2. Three-phase transformer: Used in three-phase power systems, it has high efficiency and low loss, and is widely used in industry and power transmission.
III. Classification by winding form
1. Two-winding transformer: Connects two voltage levels and is the most common type.
2. Three-winding transformer: Connects three voltage levels and is used in regional substations.
3. Autotransformer: It achieves voltage regulation through a common winding and is characterized by its small size and low cost.
IV. Classification by Cooling Method
1. Dry-type transformer: It relies on natural air cooling or forced air cooling and is suitable for places with high fire prevention and explosion protection requirements.
2. Oil-immersed transformers: These utilize transformer oil for heat dissipation and insulation, and are widely used, but fire prevention is necessary.
3. Fluoride-cooled transformer: Using fluoride as the cooling medium, it has high heat dissipation efficiency and is suitable for large-capacity applications.
1. Core-type transformer: Closed-loop core design, short magnetic circuit, low loss, suitable for high-capacity, high-voltage applications. 2. Shell-type transformer: Core enclosed in a winding, compact structure, often used in high-current equipment (such as welding machines). 3. Amorphous alloy transformer: Utilizes new magnetic materials, low no-load loss, suitable for low-load applications such as rural power grids.
1. Off-load tap-changing transformer: Voltage adjustment is required when power is off; suitable for scenarios where voltage adjustment is infrequent. 2. On-load tap-changing transformer: Voltage can be adjusted while energized; suitable for applications requiring dynamic voltage adjustment. By insulation medium: oil-immersed, dry-type, sulfur hexafluoride insulated, etc. By neutral point insulation level: fully insulated transformers and semi-insulated transformers. By conductive material: copper wire, aluminum wire, superconducting material transformers.
Two-winding transformers: These have two windings, a high-voltage winding and a low-voltage winding, used for voltage step-up and step-down transformation. Three-winding transformers: These have three windings, high-voltage, medium-voltage, and low-voltage, capable of simultaneously meeting the needs of multiple voltage levels. Autotransformers: These have only one winding but different taps, enabling voltage regulation and transformation. Autotransformers are small, lightweight, and low-cost, but their safety is relatively lower. Dry-type transformers: These rely on natural air cooling or forced air cooling, suitable for applications with special fire and explosion protection requirements. Oil-immersed transformers: These use transformer oil as a cooling medium, offering excellent heat dissipation and insulation properties. Oil-immersed transformers are widely used in power systems, but precautions must be taken to prevent oil leaks and fire risks. Core-type transformers: These have a closed core, a short magnetic circuit, and low losses. Core-type transformers are suitable for large-capacity, high-efficiency applications. Shell-type transformers: These have an open core, a longer magnetic circuit, but a compact structure, suitable for small-capacity, space-constrained applications. A transformer is an important device for transmitting electrical energy, capable of changing voltage without changing frequency. Transformers can convert high voltage to low voltage, or low voltage to high voltage, and transmit it to distant locations.
Transformers can be classified as follows: 1. By rated capacity: ① Household transformers: Transformers with a rated capacity below 1000KVA are considered household transformers. ② Integrated transformers: Their rated capacity is 200KVA-1000KVA, mostly used in substations and distribution stations, with voltage levels between 6KV and 35KV. ③ Special-purpose transformers: Generally used in production and research institutions, their rated capacity is around 200KVA-50KVA, with lower voltage levels, generally below 1KV or 500V. ④ Ultra-large capacity transformers: Their rated load is greater than 1000KVA; they are generally used in power plants or railway stations, with voltages exceeding 35KV, and even reaching 1050KV.
According to manufacturing process and structural characteristics, transformers can be classified as follows: ① Surface mount transformers: Their conductors are arranged in a disc shape, making the transformer windings lightweight and easy to install. However, they are complex to manufacture and expensive, suitable for high-frequency and high-power applications, especially in precision equipment such as computers. ② Bent-type transformers: Due to their simple winding connection method, they effectively improve equipment safety and have a small footprint, making them widely applicable. However, under heavy loads, they generate a lot of heat, making manufacturing difficult. They are often used in large and medium-sized machinery and lighting fixtures. ③ Toroidal transformers: They have a compact structure, small size, and light weight, effectively improving operational stability. Therefore, they are frequently used in applications such as radio, measurement, and other related fields.
3. Classification by transmission direction: ① Double-transmission transformer: also known as a double-connected transformer, it has two sets of low-voltage and two sets of high-voltage windings. The output voltage is the sum of the load capacities of the two sets and is transmitted to the corresponding load device. ② Single-transmission transformer: a typical example is the bridge transformer, which is a very important type of transformer. Its characteristic is that it has one set of low-voltage and one set of high-voltage windings. When the output voltage increases, the ratio of the high-voltage winding also increases; when the output voltage decreases, the ratio of the high-voltage winding decreases.
The working principle of a transformer is based on electromagnetic induction. When one winding is subjected to alternating electromagnetic excitation, the second winding will also receive the same electromagnetic excitation, thus enabling signal transmission between them. This is the principle of electromagnetic induction. In a transformer circuit, its two windings are usually referred to as the high-voltage end and the low-voltage end, connected to the input voltage power supply and the load device, respectively. The high-voltage end has a main winding and several auxiliary windings. Whether electromagnetic induction can effectively occur in a transformer depends on whether the high-voltage and low-voltage windings share a common magnetism. If there is a common magnetism between the windings, the transformer can work effectively, and the output voltage and power can be regulated normally; if the two windings cannot share a common magnetism, the transformer cannot work effectively, and the output voltage and power cannot be controlled.
