Phase loss is a special electrical fault of 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 manufacturing quality problem of the motor or a usage problem of the motor.
The motor windings burned due to phase loss have very obvious damage characteristics. 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 windings show a distribution of one phase bad and two phases good, while for the motor with star connection, it shows a distribution of two phases fault and one phase good. The faulty pole phase group is burned black or dark brown, while the remaining one or two phase windings are intact or slightly charred. 01 What manufacturing quality problems will cause the motor to run in phase loss?
Phase loss 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 terminal judgments, and the connection with the terminal board. All these links, if any link is disconnected, may cause the motor to run in phase loss.
When checking the phase failure, 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.
For the connection of the motor, we have conducted a specific analysis and discussion from the perspective of resistance balance. Recently, a friend asked about the number of motor winding joints. Regarding this issue, there is no specific regulation in the technical standards of the motor, but from the actual manufacturing reliability analysis, the joints in the winding should be minimized as much as possible, because any unreliable connection may become a cause of faults such as turn-to-turn, phase-to-phase, to ground, and phase failure; for this reason, from the perspective of design and process, the joints should be reduced as much as possible, and a reliable connection scheme should be adopted for the necessary joint positions.
Regarding the connection process of the winding, different manufacturers have different measures, but the ultimate reliability is the same requirement; in response to this problem, many equipment manufacturers have developed relatively professional equipment, which can better solve the connection between electromagnetic wires, between electromagnetic wires and lead wires, and between lead wires and terminal heads, greatly reducing the connection failures of the motor windings.
02 Phase loss failure during use
It is obviously unfair and unscientific to simply attribute the phase loss failure to the use problem, but most of the phase loss failures are caused by inappropriate 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 directly affect the normal operation of the motor. Therefore, regular and irregular inspections are the key to maintenance to 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 emerged. It seems to increase some costs, but the safety of motor and equipment operation reduces accident losses from another level.
asynchronous electric motor with squirrel-cage rotor,
three phase asynchronous fan-cooled electric motor with squirrel-cage rotor,
