During the manufacturing and assembly process of the motor, the insulation damage of the winding often causes the coil short circuit or open circuit fault. The winding is the core part of the motor. Aging, moisture, heat, erosion, foreign matter intrusion and external force impact can cause damage to the winding. Motor overload, undervoltage, overvoltage and phase loss operation can also cause winding failure. During the operation of the motor, excessive current, excessive power supply voltage fluctuations, single-phase operation, mechanical damage and poor manufacturing can easily cause the insulation damage of the winding, causing the winding to short-circuit. Winding short circuit is divided into winding turn short circuit, winding short circuit, winding pole short circuit and winding phase short circuit.

    The insulation of motor windings can be divided into main insulation, inter-turn insulation , inter-phase insulation and inter-layer insulation. The aging process of motor insulation is relatively complicated. Due to different design and process factors and operating factors during use, the main causes of failure are oxidation, wear, fatigue, high temperature, electrical stress, etc. Most low-voltage small and medium-sized motor stator winding failures are caused by inter-turn insulation damage during transient processes. Practice has shown that operating overvoltage is one of the main causes of motor insulation damage. Overvoltage can cause a very high voltage gradient on the turn insulation of multi-turn coils, and sometimes even a voltage with an impact strength of 0.1ps rise time . The breakdown site is mostly in the terminal part, especially the bend and the nose.

    As a rotating machine, the winding insulation of the motor should first have sufficient mechanical strength, wear resistance and elasticity, while ensuring the stability of electrical performance. The premise for ensuring these conditions is the stability of the performance of the insulating medium itself during the operation of the motor. As the heart of the motor, the life of the electromagnetic winding is a necessary condition to ensure the overall life of the motor. The reliability of the motor depends to a large extent on the quality of the winding insulation. In general, a good quality motor can ensure that its operating life is redundant or higher than its expected life. The life of the motor winding is greatly affected by external conditions. Ideally, the motor winding insulation should work reliably for more than 20 years. Under normal circumstances, the service life is about 5 to 8 years. A motor with good maintenance may reach more than 10 years. If it is used frequently and the environmental conditions are harsh, it should be at least 2 years.