Phase loss is an electrical fault unique to three-phase motors. It may occur during the test phase of the motor or during the use phase of the motor. It may be a problem with the manufacturing quality of the motor or a problem with the use of the motor.

The damage characteristics of the motor winding that has burned due to phase loss are very obvious. Observing from the end of the motor winding, you can see the burn marks that are distributed very regularly. For the motor with triangle connection, the winding shows a distribution of one phase bad and two phases good, while for the motor with star connection, it shows a distribution of two phases faulty and one phase good. The faulty pole phase group is burnt black or turns dark brown, while the remaining one or two phase windings are intact or slightly burnt.

Phase-missing operation can be attributed to connection failure. The connection problems involved in the motor manufacturing process include the connection of single-phase windings, the connection between windings and lead wires, the connection between lead wires and terminals, and the connection to the terminal board. Any disconnection in any of these links may cause the motor to run in phase-missing mode.

When checking for a phase loss fault, if it is a connection problem inside the motor, it can basically be attributed to a manufacturing quality problem; otherwise, it is a problem with the use of the motor.

It is obviously unfair and unscientific to simply attribute the phase loss failure to the usage problem, but most of the phase loss failures are caused by improper use. The switch is involved in the process of connecting any motor to the power supply. The performance compliance of the switch, the connection between the power cord and the motor, and the compliance of the power supply line all directly affect the normal operation of the motor. Therefore, regular and irregular inspections are the key to maintenance and avoid such problems.

In order to avoid such problems, especially for large motors and high-voltage motors, control devices such as phase loss protection, overcurrent and overvoltage protection, and current and voltage imbalance protection have come into being. Although it seems to increase some costs, the safety of motor and equipment operation has reduced accident losses from another level.