Views: 0 Author: Site Editor Publish Time: 2024-12-31 Origin: Site
Three-phase transformer is a kind of electrical equipment which can increase or decrease the voltage of three-phase alternating current. It is widely used in power system.
Structure and material: Usually the silicon steel sheet with high permeability is laminated, and the surface of the silicon steel sheet has an insulating coating to reduce eddy current loss. The structure of the iron core has two kinds of core and shell, the winding of the core core is surrounded by the core column, the shell core is surrounded by the core winding, and the three-phase transformer uses the core structure.
Function: As a magnetic circuit, it provides a closed path for the three-phase alternating magnetic flux, so that the magnetic flux can effectively pass through the winding and realize the mutual conversion of electric energy and magnetic energy.
Material and winding: Generally made of copper or aluminum wire wound, wire surface with an insulating layer. According to the voltage level and capacity requirements of the transformer, the number of turns and wire diameter of the winding will be different.
Classification and connection: divided into primary winding and secondary winding, the primary winding is connected to the power supply, the secondary winding is connected to the load. Three-phase transformers have three phase windings, which are arranged in different types on the core, and the common connection modes are Y (star) and Delta (triangle). Through different connection modes, different voltage transformation and phase relationship can be realized.
Tank: Usually made of welded steel plates, used to hold transformer oil, providing insulation and heat dissipation medium for the winding and iron core.
Transformer oil: with good insulation performance and heat dissipation performance, it can play an insulating role between the winding and the iron core, and transfer the heat generated during the operation of the transformer to the tank wall and the radiator, and distribute it to the surrounding environment through the heat dissipation device.
Oil pillow: Installed on the top of the oil tank, connected to the oil tank through the connecting pipe, used to adjust the volume expansion and contraction of the transformer oil due to temperature changes, and keep the oil level in the oil tank within the normal range.
Radiator: usually a tube or sheet structure, installed on both sides of the tank or around, by increasing the heat dissipation area, speed up the heat dissipation of the transformer oil, improve the heat dissipation efficiency of the transformer.
Tap changer: used to change the number of turns of the transformer winding, so as to adjust the transformer ratio to adapt to different grid voltage or load requirements, to achieve the adjustment of the output voltage.
Gas relay: Installed on the connecting pipe between the fuel tank and the oil pillow, used to monitor the fault inside the transformer. When there is a slight fault inside the transformer, the gas relay will send an alarm signal; When a serious fault occurs, the power supply of the transformer will be automatically cut off to protect the transformer equipment.
Pressure release valve: When the internal pressure of the transformer is too high, the pressure release valve will automatically open to release the pressure in the tank to prevent serious accidents such as explosion due to excessive pressure.
Cost reduction: When the three-phase transformer is manufactured, it shares an iron core and shell, which reduces the use of materials, occupies less space, and saves production hours, making the manufacturing cost lower.
Complete magnetic circuit: the three-phase magnetic circuit of the three-phase transformer is interrelated and compact, the symmetry of the magnetic circuit is good, the magnetic resistance is small, and the core material can be used more effectively, reducing the excitation current and iron loss, and improving the efficiency and power factor of the transformer.
High voltage balance: can well maintain the balance of three-phase voltage, output stable three-phase AC. This is very important for the normal operation of three-phase loads to avoid equipment failure or reduced operating efficiency caused by three-phase voltage imbalance.
Reliable operation
Strong structure: the winding and iron core of the three-phase transformer are assembled in an integral fuel tank, compact structure, strong integrity, can withstand large mechanical stress and electromagnetic force, and it is not easy to loose or displace parts during operation, reducing the power failure caused by mechanical failure.
Fewer points of failure: Because the internal structure is relatively simple, the connection points are relatively few, compared with the system of multiple single-phase transformers, the fault points caused by poor contact of the connection parts and insulation aging are reduced, and the reliability and stability of operation are improved.
Replacement and maintenance inconvenience: when a phase of the three-phase transformer fails, it is usually necessary to remove the entire transformer from the system for repair or replacement, unlike the single-phase transformer group, which can be replaced separately, which may lead to a longer power outage time and affect the continuity of power supply.
Phase-to-phase insulation challenge: The three-phase winding of the three-phase transformer is on the same iron core, and the distance between each other is relatively close, and good phase-to-phase insulation is needed to prevent short-circuit between phases. This puts forward higher requirements for the performance of insulation materials and the design of insulation structures, increasing the cost of insulation and the complexity of manufacturing process.
Overvoltage resistance problem: In the power system, the three-phase transformer may suffer from various overvoltages such as lightning overvoltage and operating overvoltage. Due to the complexity of its internal insulation structure, once overvoltage breakdown occurs, it is difficult to repair, and may cause serious damage.
