Why Does Insulation Varnish Peeling After Motor Winding Impregnation?

Impregnation is a critical step in the winding insulation treatment process. After impregnation, the windings undergo a necessary baking process, during which the insulating varnish bonds and cures the electromagnetic wires and other materials into a solid, integrated unit. This ensures that the winding's insulation performance and mechanical properties meet the required specifications.

However, in actual operation, insulation varnish peeling occurs from time to time - that is, the adhesion and compatibility of the insulating varnish are poor. Regarding this issue, similar problems are also encountered during the surface spray coating process of motors. A common example is the anti-rust paint on castings reacting with the topcoat applied during spray painting, resulting in bubbling and peeling. In the case of motor winding impregnation, after the varnish has been baked, it may end up in a brittle, crisp state - meaning it easily separates from the windings, and the winding fails to form a solid, cohesive unit.

Apart from quality issues with the insulation varnish itself, certain adverse conditions during the manufacturing process can also prevent the varnish from adhering properly. For instance, if oily substances contaminate the windings during handling, the varnish will not bond effectively. This is analogous to the situation where surface paint fails to adhere to motor surfaces that have been contaminated with grease or lubricating oil.

Personnel who have participated in the inspection and repair of motors with winding faults will have observed that when a winding is burned out - either partially or entirely - due to an electrical fault, the insulation varnish invariably becomes brittle and crisp and leads to insulation vanish peeling. This clearly demonstrates that high temperature is a major factor contributing to insulation varnish peeling.

During the actual operation of a motor, when the winding temperature rise is excessive, it causes the degradation of all insulating materials within the winding. Once the insulation varnish becomes brittle, the winding turns loose. This not only compromises the overall insulation performance but also leads to increased vibration and noise during motor operation, seriously affecting the motor's reliability.

Therefore, for controlling the winding impregnation process, two aspects must be ensured. First, the motor's impregnation process must comply with the specified requirements and be strictly implemented. Second, all related processes must also meet the required standards - particularly the control and consideration of temperature rise levels during application.