Analysis of the Causes of Motor Phase Loss

18/05/2019

Analysis of the Causes of Motor Phase Loss
For a three-phase asynchronous motor, the normal operation is that a three-phase symmetrical alternating current is passed into the three-phase symmetrical stator winding to generate a circular rotating magnetic field, when the three-phase current is missing one phase. The motor will behave abnormally. The main causes of phase loss of the motor are as follows.
1, the power phase is missing
Before the three-phase power supply is connected to the AC motor. The power supply has one or two phases less (the power supply has been faulty, and the melt of one phase in the three-phase fuse is blown), which can cause the motor to fail to start or start abnormal operation.
2. The terminal block in the motor junction box is loose
One phase winding of the three-phase winding of the motor stator is disconnected. This causes the motor to run out of phase.
3, the joint head is connected or broken
The joint in the power supply line may be disconnected or may be broken by an external force, which may also cause the motor to be out of phase.
4, the control loop caused a lack of phase
The contactors and relays in the control loop are used for a long time, and the contacts may have a certain degree of oxidation. Causes poor contact, or long-term wear of the component action mechanism. These electrical components are malfunctioned by the impact of the motor starting current (generally 5-7 times the rated current), or by the vibration of the electromechanical equipment or the malfunction of the moving mechanism, and the stator winding is thus phase-deficient.
5, insulation aging
After the motor has been running for a considerable period of time, the insulation of the stator winding may be aging (the ambient temperature of the motor running is too high for a long time. When the supply voltage is too high or the load is too large), the stator windings of the motor are short-circuited between phases, and the stator winding of the motor One or more phase breaks can also occur.