Insulation class of dry type transformers

Every transformer is insulated, and the insulation of a transformer is critical to the operation of the transformer itself. The insulation of dry-type transformers is graded.

Dry-type transformers refer to transformers that are not immersed in insulating oil and only consist of iron cores and coiled wires. Widely used for lighting in public places and high-rise buildings. The transformer is simple in structure, simple in manufacture, and has many advantages.

This transformer has three shapes. A good one to see. It is a transformer that is in direct contact with the air. This transformer has good heat dissipation performance, but it is easy to get wet. This transformer needs to be placed in a relatively dry room. Another is closed. This transformer has high safety and good sealing performance. Mine and several dangerous work points are used, however, the heat dissipation effect is bad. The last one is a dry-type transformer with injection type, filled with resin material. It can achieve good heat dissipation and safety performance, but generally small in size, so it is only suitable for small power use.

The insulation level of dry-type transformers is not the allowable range of temperature rise from the perspective of insulation strength, that is, the insulation level refers to the heat resistance level of the insulating material used, and is classified as a, e, B, F, H class.

The allowable temperature rise of dry-type transformers varies depending on the insulation level. The average temperature rise value in the rated current of a-class insulation is 60 K, E-class insulation is 75 K, B-class insulation is 80 K, F-class insulation is 100 K, and H-class insulation is 125 K. When the operating conditions are not the specified scale, The temperature rise value shall be determined through negotiation between the two parties. The higher the temperature, the higher the winding resistance of the dry-type transformer, the higher the temperature and the lower the heating efficiency. If it is an F-class insulation system, it is generally suitable for use at 50-60°C.