1. According to the phase number of a single transformer, the test transformer can be divided into three-phase test transformer and single-phase test transformer.

In the three-phase power system, the general application of three-phase test transformer, when the capacity is too large and limited by transportation conditions, in the three-phase power system can also be used three single-phase test transformer group.

2. According to the number of windings, it can be divided into double winding test transformer and three winding test transformer.

The usual transformer is a double winding transformer, that is, there are two windings on the core, one is the original winding, a secondary winding. The three-winding test transformer is a large capacity transformer (above 5600 kVA), which is used to connect three different voltage transmission lines. In special cases, there are also test transformers with more windings.

3, according to the structure to classify, can be divided into iron core type test transformer and iron shell type test transformer.

If the winding is wrapped in the periphery of the core is the core test transformer; If the core is wrapped around the winding, it is an iron-clad test transformer. Iron core type test transformer and iron shell type test transformer in the structure is slightly different, there is no essential difference in principle. Power transformers are usually of the tied core type.

4, according to insulation and cooling conditions, can be divided into oil immersed transformer and dry transformer.

To enhance insulation and cooling conditions, the transformer core and windings are immersed together in a tank filled with transformer oil. In special cases, such as in street lighting, mine lighting, dry transformers are also used.

In addition, there are some special purpose transformers. For example, high voltage transformers for testing, transformers for furnaces, transformers for welding, transformers for thyristor circuits, voltage transformers and current transformers for measuring instruments.