All the repair electricians who have had the experience of motor (in fact, most of them refer to three-phase asynchronous motor) winding burning and rewinding may have noticed a phenomenon that the normal operation service life of the motor repaired by winding rewinding will be significantly reduced compared with the original even if the wire embedding process and installation process meet the requirements. Moreover, the more the motor has been repaired, the shorter its service life will be.

So what is the cause of this situation? In addition to the above wire embedding process, installation process, and even the quality problems of enamelled copper wire, we can easily find the crux of the problem - whether the influence of temperature factor is considered in the old winding removal process!

At present, there are no other ways to remove the motor winding burning: open fire heating, electric furnace baking and rare high current heating. However, when using these three methods, most operators rely on experience to heat, and it is rare to use professional temperature controllers. Therefore, because of the difference brought by different experience grasp degrees, the heating temperature often exceeds the safe value that the stator core can withstand (generally, the value is about 180-210 ℃ for motors), and then the insulation between the silicon steel sheets of the stator core is seriously damaged!

Moreover, through a hot baking at too high temperature, the stator core silicon steel sheet is undoubtedly equivalent to being "annealed" once, and the magnetic flux of the core silicon steel sheet is greatly reduced! As a result, the iron loss of the motor that has passed this repair has increased significantly! This is also the root cause of the above failure!

To sum up, for motor winding rewinding repair work, in addition to ensuring that the wire embedding process on the exposed surface and the whole machine installation process meet the requirements, attention should be paid to seemingly insignificant winding removal, painting and other processes requiring temperature heating treatment, otherwise the legacy can not be ignored!