Failure and maintenance of box-type transformers
Writer： Hengfeng you electric Time：2023-04-14 views：times
To repair a box-type transformer, we must first find out the cause of the transformer failure. There are many reasons for transformer failure. Common transformer faults are usually caused by various reasons such as short circuit, open circuit and leakage. Why do transformers produce these faults? In general, it can be summarized in three aspects: one is design errors; the other is poor product quality; and the third is the use conditions exceed the design requirements.
When the transformer winding is short-circuited, the specific manifestation is that the transformer temperature is too high, there is a burning smell, smoke, the output voltage is reduced, and the output voltage is unstable. If these phenomena are found, the power supply should be cut off immediately for inspection.
The main reason for transformer short circuit is: damp in the transformer will cause internal mold growth, which will damage the insulation layer over time and cause serious leakage or short circuit; long-term aging of transformer insulation materials and reduced insulation performance will cause insulation breakdown and short circuit. In addition, a sudden increase in the power supply voltage can also cause insulation breakdown and winding short-circuits.
There is no output voltage when the transformer is open, and the primary input current is very small or there is no input current. The main reasons for the disconnection of the transformer are: the external lead wire is broken; the lead wire is disconnected from the solder lug; after the wire package is damp, it breaks due to collision and internal mold damage.
After finding the cause of the transformer failure, the transformer can be repaired. For external faults, such as disconnection or unordered, you can re-solder and replace with a new wire; if the lead terminal and the iron core are ignited or the fire between the terminals causes the insulation to burn, you should properly pull the terminal and the iron core or the terminal and the terminal. If the insulation layer is burned out, replace the insulation layer or remove the burnt part, and seal it with epoxy glue.
For transformers with damp short-circuit or large no-load loss, if the coil has been short-circuited, the short-circuit wire package must be removed and re-wound. Generally, transformers that are not short-circuited by moisture shall not be energized to avoid breakdown of the insulation layer. They can be dried in a drying oven to restore their insulating properties.
If the no-load loss is large, but the insulation resistance (between the coils, between the coil and the buckle core) is normal, it may be that the core of the box transformer is of poor quality, the core loss is large, or the coil is partially short-circuited. Check the short-circuit tester, etc., and continue using it after troubleshooting. If an open circuit, short circuit and other faults are found inside the transformer, the transformer must be removed for repair, and the following steps can be performed.
Take off the iron core. Transformers are usually filled with materials such as asphalt and wax. Before disassembly, the transformer should be heated to melt. In addition, the transformer lead should be soldered to the terminal and the fixing clip should be removed. Pull it out piece by piece. When removing the silicon steel sheet, be careful not to damage the coil lead to avoid the silicon steel sheet from breaking and bending. Then, collect the removed silicon steel sheets and wrap them in paper to avoid losing and damaging the insulating layer.
The second step is to disassemble the coil. After removing the iron core, first check whether the appearance of the coil is damaged, and then use an insulation resistance meter to check which coil the fault occurs on, so that the fault can be eliminated purposefully. Note down the interlayer insulation, wire diameter, number of turns, number of layers, etc. during disassembly for reference when rewinding. At the same time, pay attention to protect the outer skin of the wire insulation paint for repeated use; pay special attention to finding and discovering the reasons for the short circuit and open circuit of the coil. When the faulty part is found and processed, it can be re-wound according to the original winding method. After the winding is repaired, a comprehensive test and inspection can be carried out. After all the indicators meet the requirements, you can continue to use it.
