Several days ago, our Mozambique customers ordered our 5X8 egg tray production line. Recently, they also ordered the power transformer.

The role of power transformer is mainly used to change the AC voltage. Power transformer mainly contains: incoming line voltage, outgoing line voltage, variable parameter KVA. There are currently two most popular transformers: dry-type transformers and oil-immersed transformers.

Similarities and differences between dry-type transformers and oil-immersed transformers

“The same thing is that all power transformers have iron cores used as magnetic circuits and windings for circuits. The biggest difference is between the “oil type” and the “dry type.” That is to say, the cooling medium of the two is different, the former transformer oil is used as the cooling and insulating medium, and the latter uses air or other gases such as SF6 as the cooling medium. The oil change is to place the body composed of iron core and windings in an oil tank filled with transformer oil. Frequently, the iron core and windings are encapsulated with epoxy resin. There is also a non-encapsulated type, which is more used now. The windings are impregnated with special insulating paper and special insulating varnish, etc., to prevent windings or iron cores.
In terms of output and consumption, the current dry transformer voltage grade is only 35kv, and the capacity is smaller than oil transformers, about 2500kVA. And because the dry transformer manufacturing process is more complicated than oil transformers of the same voltage grade and capacity, the cost is also high. So at present, the amount of oil is still increasing. However, due to its environmental protection, flame retardant, impact resistance, etc., it is often used in indoor and other high-demand power supply and distribution places, such as hotels, office buildings, high-rise buildings, and so on.

The biggest difference between oil-immersed transformers and dry-type transformers is whether there is “oil”. Since oil is liquid and has fluidity, oil-immersed transformers must have a shell. The inside of the shell is transformer oil, and the transformer is immersed in the oil. The coil of the transformer cannot be seen from the outside; while the dry-type transformer has no oil, the outer shell is not needed, and the coil of the transformer can be directly seen; another feature is that there is an oil pillow on the oil-immersed transformer, which is stored inside transformer oil, but now new oil-immersed transformers are also produced without oil pillows.
In order to facilitate the heat dissipation of the oil-immersed transformer, which is to facilitate the flow of internal insulating oil, a radiator is designed on the outside, just like a heat sink, while the dry-type transformer does not have this radiator. The heat dissipation depends on the fan under the transformer coil. The fan is a bit like an indoor unit of a household air conditioner.
Oil-immersed transformers are generally installed indoors or outdoors in separate transformers due to the need for fire protection, while dry-type transformers must be installed indoors. Generally, they are installed in low-voltage power distribution rooms and installed side by side with low-voltage power distribution cabinets.

The difference between dry-type transformers and oil-immersed transformers

1. Appearance. Different packaging forms, dry-type transformers can directly see the iron core and coil, while oil-type transformers can only see the outer shell of the transformer.
2. Different lead forms. Dry-type transformers mostly use silicone rubber bushings, while oil-type transformers mostly use porcelain bushings.
3. The capacity and voltage are different. Dry-type transformers are generally suitable for power distribution. Most of the capacity is below 1600KVA, the voltage is below 10KV, and some have 35KV voltage levels; while oil-type transformers can achieve full capacity and voltage levels from small to large. Voltage: The UHV 1000KV test circuit under construction in my country must use oil-type transformers.
4. Insulation and heat dissipation are different. Dry-type transformers are generally insulated by resin and are cooled by natural air. The large capacity is cooled by fans, while oil-type transformers are insulated by insulating oil. The circulation of insulating oil inside the transformer transfers the heat generated by the coil to the radiator of the transformer.
5. Applicable places. Dry-type transformers are mostly used in places where “fire and explosion-proof” are required. Generally, large buildings and high-rise buildings are easy to use. Oil-type transformers may be sprayed or leaked after an accident, causing fires. Most of them are used outdoors. And there is a place for digging and setting up an “accident oil pond”.
6. Different load bearing capacity. Generally, dry-type transformers should be operated under rated capacity, while oil-type transformers have better overload capacity.
7. The cost is different. For transformers of the same capacity, the purchase price of dry-type transformers is much higher than that of oil-type transformers.

Advantages and disadvantages of dry-type transformers and oil-immersed transformers

Each has its own advantages and disadvantages. The oil conversion cost is low and maintenance is convenient, but it is combustible and explosive. Because of its good fire resistance, the dry transformer can be installed in the central area of the load to reduce voltage loss and power loss. However, dry transformers are expensive, large in size, poor in moisture and dust resistance, and noisy.
The price becomes more expensive than oil.
In terms of capacity, large-capacity oil becomes more than dry.
Dry transformers are required in comprehensive buildings (basements, floors, roofs, etc.) and densely populated fields. The oil transformer is used in an independent substation.
The transformer in the box change generally adopts the box change. Oil transformers are generally used for temporary outdoor electricity use.
During construction, choose dry and oil changes according to the space. You can choose oil changes when the space is large, and dry changes when the space is more crowded.
The regional climate is relatively humid and sultry, and it is easy to use oil change. If dry change is used, it must be equipped with forced air cooling equipment.