Phase number to distinguish

It can be divided into three-phase transformer and single-phase transformer. In the three-phase power system, the general application of three-phase transformer, when the capacity is too large and restricted by transport conditions, in the three-phase power system can also be applied to three single-phase transformer composition transformer group.

Winding to distinguish

It can be divided into double winding transformer and three winding transformer. Usually transformers are double-winding transformers, that is, there are two windings on the iron core, one is the original winding, one is the secondary winding. Tri-winding transformers are large-capacity transformers (above 5600 kVA) used to connect three different voltage transmission lines. In special cases, there are also Satons transformers that apply more windings.

Structure classification

It can be divided into iron-core transformer and iron-shell transformer. If the winding package in the core periphery is a core type transformer; If the iron core is wrapped around the periphery of the winding, it is an iron-clad transformer. The two are slightly different in structure, but there is no essential difference in principle. Power transformers are of core type.

The transformer is mainly composed of iron core, winding, oil tank, oil pillow, insulation bushing, tap switch and gas relay.

The iron core

The iron core is the magnetic circuit part of a transformer.Hysteresis loss and eddy current loss are generated during operation.In order to reduce heat loss and volume and weight, the core is composed of cold-rolled grain oriented silicon steel sheet with high magnetic conductivity less than 0.35mm.According to the arrangement of winding in the core, there are core type and shell type.

In the transformer of large capacity, in order to make the heat generated by the loss of the iron core can be fully taken away by the insulating oil during the cycle, so as to achieve good cooling effect, the cooling oil channel is often provided in the iron core.

The winding

The winding and iron core are the core components of the transformer. Because there is resistance in the winding itself or contact resistance in the joint, heat should be generated by Joule's law.Therefore, the winding cannot pass a current higher than the rated current for a long time. In addition, the short-circuit current will produce a large electromagnetic force on the windings and damage the transformer.Its basic winding has concentric type and overlap type two kinds.

The main faults of transformer windings are short circuit between turns and short circuit to the shell.Interturn short circuit is mainly due to insulation aging, or due to the transformer overload and through the short circuit insulation by mechanical damage. The oil surface in the transformer drops, so that the winding is exposed to the oil surface, interturn short circuit can also occur;In addition, when passing through short circuit, due to the over-current effect of the winding deformation, so that the insulation is mechanical damage, will also produce inter-turn short circuit. In the case of interturn short circuit, the current in the short circuit winding may exceed the rated value, but the current in the whole winding may not exceed the rated value. In this case, the gas protection action, serious situation, the differential protection device will also be in action.The reason for the short circuit of the shell is also due to aging insulation or oil damp, oil level drop, or due to lightning and operating overvoltage. In addition, when passing through the short circuit occurs, the winding will be deformed due to the over-current, and the short circuit phenomenon will also occur to the shell. When the shell is short circuit, it is generally the action of gas protection device and ground protection action.

The fuel tank

The body (winding and iron core) of the oil-immersed transformer is installed in the oil tank filled with transformer oil, and the oil tank is welded with steel plates. The oil tank of the medium and small transformer is composed of a box shell and a box cover. The transformer body is placed in the box shell. The box cover can be opened to be lifted out of the body for maintenance.

Performance features for editing speech

A. In addition to copper wire for small capacity, the low-voltage winding of oil-immersed transformer generally adopts the cylinder structure of copper foil around the shaft; The high-voltage winding adopts multi-layer cylinder structure, so that the distribution of ampere-turns is balanced, the magnetic leakage is small, the mechanical strength is high, and the short-circuit resistance is strong.

B. Fastening measures are adopted for the core and winding respectively. Fastening parts such as the height of the device and the low-voltage lead wire are all equipped with self-locking anti-loosening nuts, and the structure without lifting core is adopted to withstand the shock of transportation.

C. Coil and core using vacuum drying, transformer oil using vacuum oil filter and oil injection process, so that the transformer internal moisture to a minimum.

D. The oil tank adopts corrugated sheet, which has the breathing function to compensate the volume change of oil caused by the temperature change, so the product has no oil storage tank, which obviously reduces the height of the transformer.

E. Because the corrugated sheet replaced the oil storage tank, the transformer oil is isolated from the outside world, so as to effectively prevent the entry of oxygen and water and lead to the decline of insulation performance.

F. According to the above five points, the oil-immersed transformer does not need to change oil in normal operation, which greatly reduces the maintenance cost of the transformer and prolongs the service life of the transformer.