analyze the problem of transformer short-circuit resistance

Source:AdminAuthor:WPOWER Addtime:2020-06-01 Click:
Power adapter manufacturers analyze the problem of transformer short-circuit resistance. The lack of short-circuit resistance of the transformer itself is the main reason for the transformer accident, especially the short-circuit resistance of the new transformer is particularly prominent.
1. In the design of the transformer structure, the electromotive force acting on the transformer windings is calculated only by statics, and it cannot correctly reflect the various stresses of the transformer when it is subjected to sudden short-circuit current impact. In view of the structure of the transformer, the coil is usually composed of paper-coated copper separated by insulating pads. The elasticity of the insulating pads is related to the degree of compression, that is, to the force. Because electric power changes according to complex laws. Therefore, the relationship between the force and deformation of each part of the winding when the transformer is short-circuited is also complicated and changes with time. Therefore, the dynamic process must also be analyzed.
2. The axial compression force of the winding is not enough. There are two reasons for this problem. One is that some manufacturers have not pursued the saving of end insulation distance and reduced additional loss according to the current status of domestic materials and processes. They blindly adopt the same insulation pressure plate structure and ignore the density of the pad Treatment; Second, the process quality is poor, resulting in a significant height difference between the upper part of the high and low voltage windings, resulting in a major quality problem.
3. The material and shape of the pressure plate affect the axial strength. Some transformer laminated wood pressure plates use two semi-circular pressure plates. Some of the pressure plates are not strong enough. Sometimes the transformer is broken after a sudden short circuit. For serious use of multiple pressure plates, the method of building blocks is used. Such as Heze Power Plant's No. 0 start-up change.
The lead fixing point is not enough, and the bracket is not firm. After the transformer is short-circuited, the wooden bracket holding the lead of the transformer is broken and the wooden screw is broken, or the transformer is elastically deformed under the action of high-current impact electric power, resulting in insulation breakdown of the lead under the operating voltage. Insufficient support between the inner winding and the core post. The inner winding of some transformers is lined with a soft paper tube. Under the action of radial force, the inner winding is often squeezed toward the core, which causes the main insulation of the high-voltage special transformer to damage and burn the core.         

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