Principle and structure of dry-type transformer
Writer： Hengfeng you electric Time：2023-04-23 views：times
Simply speaking, dry-type transformer refers to the transformer whose core and winding are not immersed in insulating oil.
Dry type transformer uses electromagnetic induction principle to transfer power and signal from one circuit to another, which is an important factor in power transmission and signal transmission. Its working principle is the same as that of other transformers and follows the physical principle of electromagnetic coupling. Due to mutual inductance between two circuits, the current change of one circuit affects the other circuit through mutual inductance. There is close cooperation and interaction between the input and output of two or more circuit elements or electrical networks, and energy is transferred from one side to the other through interaction.
The structure type of dry-type transformer is mainly composed of an iron core composed of silicon steel sheets and an epoxy resin cast coil. Insulating cylinders are placed between high and low voltage coils to increase electrical insulation, and the coils are supported and restrained by cushion blocks. Fasteners for overlapping parts of dry-type transformer have anti loosening performance.
There are three types of dry-type transformers.
1. Open type: It is a common type. Its body is in direct contact with the atmosphere and is suitable for relatively dry and clean rooms (the relative humidity should not exceed 85% when the ambient temperature is 20 ° C). Generally, there are two cooling modes: air self cooling and air cooling.
2. Closed type: the device is located in a closed enclosure and does not directly contact the atmosphere (due to poor sealing and heat dissipation conditions, it is mainly used for mining and belongs to explosion-proof type).
3. Pouring type: epoxy resin or other resins are used as the main insulation, which is simple in structure and small in size, and is suitable for transformers with small capacity.
1. Temperature control system
The safe operation and service life of dry-type transformer largely depend on the safety and reliability of transformer winding insulation.
2. Cooling mode
The cooling mode of dry-type transformer is divided into natural air cooling (AN) and forced air cooling (AF). In case of natural air cooling, the transformer can operate continuously for a long time under rated capacity. In case of forced air cooling, the output capacity of transformer can be increased by 50%. It is applicable to intermittent overload operation or emergency overload operation; Due to the large increase of load loss and impedance voltage during overload, it is in a non economic operation state, so it should not be in a long-term continuous overload operation.
Dry type transformer and oil immersed transformer are the two most widely used transformers. Compared with oil immersed transformer, dry type transformer has good fire protection performance and is commonly used in hospitals, airports, stations and other places with high fire protection requirements, but the price is relatively high and there are certain requirements for the environment. For example, it should not be too wet, and there should not be too much dust and dirt. In addition, the operation maturity of dry-type transformer is not as mature as that of oil immersed transformer.
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