Dry-type transformers are mainly divided into two types of impregnated dry-type transformers and resin dry-type transformers.
Impregnated dry - type transformers
Domestic impregnated dry-type transformer wire using glass fiber package, pad with the corresponding insulation material hot forming, used for hydropower stations, high-rise buildings, fire good.
The main insulation is the insulation between the winding and the winding and between the winding and the core. The insulation of the transformer is divided into B, F, H, C,
Vertical insulation refers to the transformer winding has different potentials of different points and different parts of the insulation, including winding turns, inter-layer and between the insulation performance. ) Of the airway all the air as an insulating medium.
Such transformers are more affected by the environment than the resin-type dry-type transformers, the appearance and weight are also large, at home and abroad are tending to reduce production.
Winding at both ends of the end seal, not afraid of tide, fire strong ability, can be in the fire 750 ℃ under fire, is a relatively new dry-type transformers. 1.2 resin dry-type transformers represent the current domestic resin casting
The three types of products, in the manufacture and performance of the products have their own characteristics, the current market also occupy a certain market share,
Wirewheel-type transformer structure characteristics In the second power plant in Baoji, Shaanxi, the factory dry-type transformers are wire-wound casting transformer, the voltage level is 6 kV, the capacity of 100 kVA to 1600 kVA, the use of indoor installation.
The product of high and low voltage winding using copper wire, full winding, glass fiber reinforced, thin insulation, resin without filler, vacuum impregnation pouring, according to the specific temperature curing curve curing molding.
High-voltage winding with a special sub-cylindrical structure, low-voltage winding depending on the voltage level selection of multi-cylinder, sub-cylindrical or special sub-cylinder.
The high-voltage winding of the wire-wound casting transformer adopts a special segmented cylinder structure. This structure is developed on the basis of ordinary segmented cylindrical windings. The ordinary segmented cylinder has inherited the advantages of the impact of the cylindrical winding , But also solve the cylindrical winding layer voltage is high contradiction, is a more ideal winding structure, often referred to as non-resonant winding structure.
The special segmented cylinder further reduces the interlayer voltage, improves the voltage distribution, and greatly increases the impact strength against atmospheric overvoltages and operating overvoltages compared to conventional segmented cylinders.
The impact resistance is not only related to the structure of the winding, but also depends on the casting quality of the casting and the electrical properties of the insulating material.
After the winding of the product is completed, it is poured with pure resin in a vacuum state without any filler, so that the flowability of the resin does not decrease.
And because the winding is made of wire wound, so the resin from the winding in the axial or radial, can be completely immersed in the winding, there is no bubble inside.
This paper introduces the classification and characteristics of dry-type transformers, and introduces the structural characteristics, technical characteristics, cooling system and temperature control system of wire-wound pouring transformers, and summarizes the development of dry-type transformers prospect. Key words: dry - type transformers; wire - wound pouring transformers.
Resin and glass fiber composed of solid insulation, not only good impact resistance, and the local discharge is very small.
Good mechanical strength
Anti-short-circuit ability to wire-wound cylindrical cylinder, the vacuum casting, regardless of the winding layer, turn between the paragraphs can be a one-time impregnated resin.
After curing, resin, wire, glass fiber tightly combined to form a solid rigid body structure. The high strength of the structure of the mechanical properties of the wirewound casting products with good resistance to short circuit capability.
Good crack resistance
(18 ~ 20) × 10-6 / K, the expansion coefficient of copper used in the winding is 17 × 10-6 / K, which is close to each other, and the difference between the two is Transformer operation due to thermal expansion and contraction caused by the winding conductor and insulation between the mechanical stress, from the root to eliminate the phenomenon of cracking.
As the product is high and low pressure are resin casting, the core is also used resin coating, so moisture and corrosion resistance. When the air relative humidity of 100%, still long-term operation.
Good heat dissipation
As the pure resin and glass fiber composite insulation has a very high electrical strength, so the product surface insulation thickness of only 1.5 ~ 2 mm, greatly improving the cooling performance of the winding surface.
Cooling systems and protection Dry-type transformers are cooled by natural air cooling and forced air circulation. The use of natural air cooling, can ensure that the transformer in the case of rated load normal operation. Baoji second power plant used in dry-type transformers are using radial fans for forced air cooling.
With forced air circulation cooling, 800 kVA and below dry-type transformers can be increased by 40%, 800 kVA or more dry-type transformers can be 50% capacity, and continuous operation.
Dry-type transformers are generally IP00 protection, that is, not with the shell, indoor use, Baoji second power plant that use this protection mode. Can also be based on user requirements, plus protective shell.
With IP20 housing, solid foreign matter greater than 12 mm can be prevented from entering, providing a barrier to the live part. IP23 protection, in addition to IP20 protection, but also has anti-water function.
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