Transformers can be said to be closely related in our daily lives. They are electronic devices that change one voltage to another. Although we rarely see transformers in our lives, the electrical appliances we use are as large as refrigerators and air conditioners. To mobile phone chargers, there are transformers in them, and the types of transformers are different due to different devices. Regarding the classification of transformers, transformers can be classified by purpose, capacity, number of windings, etc. Different types of transformers are used in different environments. The role of transformers is mainly used to change the AC voltage.

Ⅰ. Classification by purpose:

1. Power transformer

2. Electric furnace transformer;

3. Rectifier transformer;

4. Power frequency test transformer;

5. Mine transformer;

6 Reactor;

7. Voltage regulating transformer;

8. Transformer;

9. Other special transformers.

Ⅱ. Classified by capacity:

1. Small and medium-sized transformers: the voltage is below 35KV, and the capacity is 10-6300KVA;

2. Large transformer: voltage is 63-110KV, capacity is 6300-63000KVA;

3. Extra-large transformer: voltage above 220KV, capacity 31500-360000KVA;

Ⅲ. Classification according to the number of phases:

Transformers can be classified into single-phase transformers and three-phase transformers according to the number of phases.

Ⅳ. Classification according to the number of windings:

1. Dual-winding transformer A transformer with high-voltage winding and low-voltage winding;

2. Three-winding transformer A transformer with high-voltage winding, medium-voltage winding and low-voltage winding;

3. Auto power transformer The characteristic of the auto power transformer is that there is not only a magnetic coupling connection between the first and second windings, but also a direct electrical connection. Compared with ordinary transformers, the use of autotransformers can save materials, reduce costs, reduce the size and weight of the transformer, and is beneficial to the transportation and installation of large transformers.

Ⅴ. Classification according to the voltage regulation method of the transformer:

According to the voltage regulation method, it can be divided into no-load voltage-regulating transformer and on-load voltage-regulating transformer. 

Ⅵ. Classification according to the cooling medium of the transformer:

According to the cooling medium, it can be divided into oil-immersed transformers, dry-type transformers, gas-filled transformers, rubber-filled transformers, and sand-filled transformers.

Ⅶ. Classification according to the cooling method of the transformer:

1. Oil-immersed self-cooling transformer;

2. Oil-immersed air-cooled transformer;

3. Oil-immersed forced oil circulating air-cooled transformer;

4. Oil-immersed forced oil-circulating water-cooled transformer;

5. Dry-type transformer.

Ⅷ. Classified by core structure:

1. Heart-shaped transformer

2. Shell type transformer.

Ⅸ. Other categories:

1. According to the wire material classification, there are copper wire transformers and aluminum wire transformers.

2. According to the neutral insulation level, there are fully insulated transformers and semi-insulated transformers.

3. According to the number of connected generators, it can be divided into double-split and multi-split transformers, and double-split transformers can be divided into axial split and radial split transformers.

4. According to the connection classification of the high voltage winding with or without electricity, it can be divided into ordinary power transformers and autotransformers. 

Ⅹ. The role of the transformer:

1. Used to change the AC voltage, which is the origin of its name;

2. The transformer does not change the power while changing the voltage (when loss is not considered), so the current will inevitably change when the voltage changes, that is, the impedance will be changed. Therefore, in electronic technology, transformers are used for impedance matching.

3. In addition to the resistance-capacitance coupling and direct coupling, there is also transformer coupling for the inter-stage coupling of the amplifier, which can not only change the impedance, but also isolate the direct current. It's just that the transformer is large in size and poor in frequency characteristics, so it is seldom used now.