Dry-type transformer classification and characteristics
01-16 2025 | By:
Dry-type transformers are one of the types of transformers, but many friends do not know much about dry-type transformers. In order to enhance everyone’s understanding of dry-type transformers, this article will introduce the classification of dry-type transformers, the performance characteristics of dry-type transformers, and the application fields of dry-type transformers. If you are interested in dry-type transformers, you may wish to continue reading.
Introduction to dry-type transformers
Dry-type transformers rely on air convection for cooling and are generally used for local lighting and electronic circuits. Dry-type transformers are widely used in local lighting, high-rise buildings, airports, docks, CNC machinery and equipment and other places. Simply put, dry-type transformers refer to transformers whose cores and windings are not immersed in insulating oil. The cooling methods are divided into natural air cooling (AN) and forced air cooling (AF). When naturally air-cooled, the transformer can operate continuously for a long time at rated capacity. When forced air cooling, the transformer output capacity can be increased by 50%. It is suitable for intermittent overload operation or emergency accident overload operation; due to the large increase in load loss and impedance voltage during overload, it is in a non-economic operation state, so it should not be in long-term continuous overload operation.
Classification of dry-type transformers
Dry-type transformers are transformers whose cores and windings are not immersed in insulating liquids. They are used in general public distribution networks or industrial power grids and can be divided into the following three categories:
(1) Fully enclosed dry-type transformers: transformers placed in a pressure-free sealed casing and cooled by internal air circulation.
(2) Enclosed dry-type transformers: transformers placed in a ventilated casing and cooled by external air circulation.
(3) Non-enclosed dry-type transformers: transformers without protective casings that are cooled by natural or forced air circulation.
Performance characteristics of dry-type transformers
High safety: SG10 transformers do not contain flammable resins, do not support combustion during use, are flame retardant, will not explode or release toxic gases, will not cause harm to the environment, other equipment and human body, and are insensitive to humidity, dust and pollution; there is no partial discharge during operation and there is no possibility of “cracking”.
High reliability: Both high and low voltage coils are made of NOMEX insulation material, and are impregnated with H-class solvent-free impregnation paint multiple times by VPI vacuum pressure equipment, and cured by high temperature baking multiple times. The product is H-class (180℃), and the main insulation material is C-class (220℃), with strong overload capacity and good short-circuit resistance. Under good ventilation conditions, 20% overload operation is allowed.
Energy saving and environmental protection: After the product life ends, steel, iron and other materials are easy to recycle; all NOMEX paper used will not release toxic substances when burned; other insulation materials can be degraded and will not pollute the environment; the product has low loss and energy saving; low noise and flexible design.
Application fields of dry-type transformers
In recent years, dry-type transformers have become more and more widely used, and the main application fields are:
Distribution transformers:
Voltage: The high-voltage side voltage is 10KV at most, and the highest is 35KV; the low-voltage side voltage is usually 0.4KV, which can provide AC 380V power supply for low-voltage electrical equipment and 220V power supply for urban and rural lighting and household electrical appliances.
Capacity: 30KVA to 2500KVA.
The most widely used: Power distribution for power equipment and lighting power supply for urban distribution networks, industrial and mining enterprises, etc. Transformers account for more than 80-90% of the dry-type transformer market.
Power transformer:
For 10, 20, 35KV power transformers, the production capacity can reach 630~20000KVA. In 1996, my country has manufactured a capacity of 16000KVA, 35/10KV voltage, Asia’s first dry-type transformer with the largest capacity and the highest voltage. These transformers are mostly used in power system regional substations.
Rectifier traction transformer:
Rectifier excitation transformer: The excitation system of the generator is developing towards static equipment, and dry-type transformers have a tendency to replace excitation generators. Its high voltage is 13.8KV~20KV, and the low voltage is around 1KV. It is usually a single-phase structure, and most of them are high-voltage closed busbars. The excitation transformer developed for the Three Gorges generator on the Yangtze River is expected to have a single-phase capacity of 3000KVA.
Metallurgical furnace transformer: It is characterized by low voltage and high current (my country has produced 20,000 amperes), which is used for electric furnace smelting.
Traction transformer: Dry-type traction transformer suitable for urban subway and rail transit will be widely used with the development of urban rail transit. The voltage is 10, 20, 35KV, several levels, and the capacity is 800, 2500, 3300KVA, etc. From 12-pulse rectification to 24-pulse, harmonic pollution is reduced.
Various special-purpose dry transformers:
Dry transformers are suitable for various fields and various special purposes, such as nuclear power plants, ships and offshore platforms, steel rolling and other special transformers.
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