The main forms of transformer short-circuit damage are as follows:
1. Axial instability. This damage is mainly caused by the axial electromagnetic force generated by radial leakage, resulting in axial deformation of the transformer winding.
2. The wire cake is bent and deformed up and down. This damage is caused by the long-term deformation of the wire between two axial pads under the action of axial electromagnetic force due to excessive bending moment, and the deformation between the two pads is usually symmetrical.
3. Collapse of winding or wire cake. This type of damage is caused by the wires being squeezed or collided with each other under axial force, resulting in tilting deformation. If the wire is initially slightly inclined, the axial force promotes an increase in inclination, and in severe cases, it collapses; The larger the ratio of height to width of a wire, the more likely it is to cause collapse. In addition to the axial component, there is also a radial component in the end leakage magnetic field. The combined electromagnetic force generated by the leakage magnetic field in both directions causes the inner winding wire to flip inward and the outer winding to flip outward.
4. The winding is raised to support the pressure plate. This type of damage is often caused by excessive axial force or insufficient strength and stiffness of its end support components, or assembly defects.
5. Radial instability. This damage is mainly caused by the radial electromagnetic force generated by axial magnetic leakage, resulting in radial deformation of the transformer winding.
6. The elongation of the outer winding leads to insulation damage. The radial electromagnetic force attempts to increase the diameter of the outer winding, and excessive tensile stress on the wire can cause long-term deformation. This deformation is usually accompanied by wire insulation damage, resulting in inter turn short circuits. In severe cases, it can cause the coil to be embedded, disordered, and collapse, or even break.
7. The end of the winding is overturned and deformed. In addition to the axial component, there is also a radial component in the end leakage magnetic field. The combined electromagnetic force generated by the leakage magnetic field in both directions causes the winding wires to flip inward and the outer winding to flip outward.
8. The inner winding wires are bent or warped. The radial electromagnetic force reduces the diameter of the inner winding, and bending is the result of long-term deformation caused by excessive bending moment of the wire between two supports (inner braces). If the iron core is tightly bound and the winding radial brace is effectively supported, and the radial electric force is evenly distributed along the circumference, this deformation is symmetrical, and the entire winding is a polygonal star. However, due to the compression deformation of the iron core, the supporting conditions of the support bars are different, and the force along the circumference of the winding is uneven. In fact, local instability and warping deformation often occur.
9. The lead wire is fixed and unstable. This type of damage is mainly caused by the electromagnetic force between the leads, which causes lead vibrations and leads to short circuits between the leads.