1 single phase transformer: used for single-phase load and three-phase transformer group.
(2) Three phase transformer: used for voltage rise and fall of three-phase system.
2. By cooling method:
(1) Dry type transformer: it is cooled by air convection and is generally used for small capacity transformers such as local lighting and electronic circuits.
(2) Oil immersed transformer: relying on oil as cooling medium, such as oil immersed self cooling, oil immersed air cooling, oil immersed water cooling, forced oil circulation, etc.
3. By purpose:
(1) Power transformer: used for voltage rise and fall of power transmission and distribution system.
(2) Instrument transformers: such as voltage transformers, current transformers, measuring instruments and relay protection devices.
(3) Test transformer: it can generate high voltage and conduct high voltage test on electrical equipment.
(4) Special transformer: such as furnace transformer, rectifier transformer, adjustment transformer, etc.
4. According to winding type:
(1) Double winding transformer: used to connect two voltage levels in the power system.
(2) Three winding transformer: it is generally used in the substation in the power system area to connect three voltage levels.
(3) Autotransformer: used to connect power systems with different voltages. It can also be used as a common step-up or step-down transformer.
5 according to the form of iron core:
(1) Core transformer: used for high-voltage power transformer.
(2) Shell transformer: special transformer for high current, such as furnace transformer and welding transformer; The biggest difference between the oil immersed test transformer and the dry-type transformer is whether there is oil. Because the oil is liquid and has fluidity, the oil immersed test transformer must have a shell. The inside of the shell is transformer oil, and the coil of the transformer is soaked in the oil, so the coil of the transformer cannot be seen from the outside; The dry-type transformer has no oil, so the shell is not needed, and the coil of the transformer can be seen directly; Another feature is that the oil immersed transformer has oil conservator on it and transformer oil is stored inside, but now the new oil immersed test transformer is also produced without oil conservator; For the convenience of heat dissipation, i.e. the flow and heat dissipation of internal insulating oil, the oil immersed test transformer has designed a radiator outside, just like a radiator, while the dry-type transformer does not have this radiator. The heat dissipation depends on the fan under the transformer coil, which is a bit like the indoor unit of household air conditioner;
Due to the need of fire prevention, oil immersed transformers are generally installed in separate transformer rooms or outdoors, while dry-type transformers are certainly installed indoors. Generally, they are installed in low-voltage distribution rooms, side by side with low-voltage distribution cabinets.
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