1. Electrochemical destruction

In the gas production workshop of a certain factory, two motors have malfunctioned. One of the stator windings has three insulation ruptures, and an area has "creepage" with burn marks, cracks, and conductive channels. The faulty parts are all near the motor's air inlet and have a tendency to shift towards the dead center. We began to believe that the layout, operating environment, and control methods of the electric motor system were unreasonable, and the harsh operating environment led to electrochemical breakdown.

The main cause of insulation damage in asynchronous motor test benches is the electrochemical damage caused by harsh operating environments. The acidic and alkaline corrosive gases present in the environment can corrode the outer layer of insulation materials. In high environments, it can accelerate the performance of insulation materials, and under the dual effects of electricity, heat, and chemistry, it is easy to cause damage.

2. Frequent startup

Frequent starting of high-voltage explosion-proof motors has a significant impact on their service life. This is because the electric motor is subjected to a large current shock during the starting process, and the coil has to withstand the dual effects of the motor and thermal stress. Due to the different shrinkage coefficients of coil insulation materials and copper wires, significant shear stress is generated between the insulation materials and wires during start-up, which can damage the strength of the wires and insulation materials, causing the insulation layer to rupture or break, resulting in insulation rupture.

When the squirrel cage asynchronous motor is frequently started, it is easy to cause squirrel cage breakage, especially for load starting motors, which have a higher probability of failure.

3. Embedded defects

When embedding the wire, the insulation pressure loss at the end formed by bundling is another tense part that causes damage to the high-voltage motor winding. Wherever the end ring comes into contact, there will be varying degrees of lateral compression, forming grooves, until a hardened insulation material is extruded to the edge of the bonding contact. After the entire solidification, the insulation layer of this part will become significantly thinner and the insulation strength will decrease.

4. Poor insulation quality of the end handbag

There are many examples of poor insulation quality of end handbags causing end connections or relative short circuits. The insulation layer of the handbag is loose and has gaps on the outer layer. When the humidity is high, the insulation performance of the coil will significantly decrease until the outer layer of the insulation material is exposed. At this time, the outer insulation mesh is prone to edge discharge. Its discharge mechanism is to form a natural water film on the insulation surface. Under the action of an electric field, the ionosphere ionizes and aggregates together, forming an uneven electric field distribution and reducing the external discharge voltage. This type of discharge along the outside is actually a gas dielectric discharge phenomenon, with a much lower voltage than the breakdown voltage present in many gases or solids, and occasional creeping intervals can reach tens of centimeters. Discharge along the surface can cause a series of breakdown flashover between high potentials, that is, phase to phase short circuit disorder.