Talking about motor flashover phenomenon from real life case

Fault case description

The motor is compact and the motor cavity is relatively small, but from the overall distribution of the stator windings, this problem does not occur. Further inspection revealed that blackening marks appeared on the surface of the winding end at a distance. There are some very fine iron powder below the winding area. The problem was solved by cleaning the iron powder and cleaning up the surface where the surface was ablated.

From the fault appearance and some actual anomalies, it can be basically reduced to a typical flashover; further verification is caused by the blind hole of the fixed end cover during the processing of the motor base, and the fine iron appearing during the tapping and assembly process. The powder enters the inner cavity of the motor. During the running of the motor, the iron powder in the upper and side end holes of the base is shaken to the position below the base, which "perfectly creates" the conditions under which the flashover occurs.

From the consequences of this case, we have to remind you that the holes in the motor parts seem to be simple, but when is the through hole and when it is a blind hole, it should be processed strictly according to the figure, especially for the blind hole, it must have its specific The role and reason.


What is flashover?

Flashover refers to the breakdown between two electrodes that occurs along a solid insulating surface within a gas under the action of a high voltage. The voltage between the two electrodes immediately before the occurrence of flashover is called the flashover voltage. Due to the influence of the surface state and shape of the solid insulation, the flashover voltage is always lower than (at most equal to) the spark discharge voltage of the gas gap of the same electrode structure and the same distance.

Insulators or bushings of high-voltage power transmission and transformation equipment contaminated with pollution (industrial pollution, salt, etc.), when exposed to moisture (especially in the case of fog, dew, frost or light snow), the flashover voltage is significantly reduced, even in The operating voltage of the electrical equipment flashes underneath, causing a serious accident. This condition is called contamination flash and can be prevented by improving the insulation design and regular cleaning.

When a destructive discharge phenomenon occurs along a solid insulating surface in a gas or liquid dielectric, it is called flashover. Common is the flashover that occurs along the interface between the gas and the solid dielectric. For example, a destructive discharge along the surface of the insulator string along the surface of the casing is referred to as flashover. Therefore, the word flashover is limited to the discharge phenomenon of special conditions.

Reprinted from the network