Winding
Oil-immersed transformer windings and iron cores are the core components of the transformer. Because of the resistance of the winding itself or the contact resistance at the joint, heat is generated by the I2Rt. Therefore, the winding cannot pass a current higher than the rated current for a long time. In addition, when the short-circuit current is passed, a large electromagnetic force will be generated on the winding to damage the transformer. Windings are concentric and overlapped.
Iron core
The core is the magnetic circuit part of the transformer. Hysteresis loss and eddy current loss generate heat during operation. In order to reduce the heat loss and reduce the volume and weight, the core is composed of a cold-rolled grain-oriented silicon steel sheet with a high magnetic permeability of less than 0.35 mm. According to the arrangement of the windings in the iron core, there are the core type and the iron shell type.
In order to achieve a good cooling effect, a large-capacity transformer is required to remove the heat generated by the core loss by the insulating oil during circulation, and cooling oil passages are often provided in the core.
The main faults of oil-immersed transformer windings are interturn short circuits and short circuits to the housing. Inter-turn short circuit is mainly due to insulation aging, or due to overload of the transformer and insulation damage caused by mechanical damage. When the oil level in the transformer drops, the windings can be exposed to the oil level, and a short circuit can occur. When there is a short circuit, the windings are deformed due to the over-current effect, so that the insulation is mechanically damaged and short circuit occurs. In the event of a short circuit between turns, the current in the short-circuit winding may exceed the rated value, but the entire winding current may not exceed the rated value. In this case, if the gas protection action is severe, the differential protection device will also act. The reason for the short circuit to the housing is also due to the aging of the insulation or the dampness of the oil, the drop of the oil level, or due to lightning and operating overvoltages. In addition to this, in the event of passing through a short circuit, the winding is deformed due to an overcurrent and a short circuit to the case occurs. When the shell is short-circuited, the operation of the gas protection device and the protection of the ground are generally performed.
tank
The body (windings and cores) is housed in an oil tank filled with transformer oil, which is welded with steel plates. The tanks of medium and small transformers are composed of shells and box lids. The body of the transformer is placed inside the shell. The box lid can be opened to lift the body for inspection.
The oil-immersed transformer adopts a fully-sealed structure, and the oil-immersed transformer oil is isolated from the air, slowing the change of the oil. Surface electrostatic spray, beautiful and corrosion-resistant.
Oil-immersed transformers In severe overload conditions, the coil insulation will not age and thermally breakdown, maintaining excellent electrical and mechanical properties during use. The redesigned coil gallery reduces hot spot humidity. The redesigned fuel tank increases the heat dissipation surface and ensures that the oil will not deteriorate under severe overload conditions.
