Under normal circumstances, the power supply and winding of the three-phase motor are symmetrical, when the power supply is out of phase or the motor is improperly connected, resulting in the motor input voltage is out of phase, it will cause the motor winding to appear regular burn phenomenon, observed from the end of the winding, the winding shows a very regular fancy fault appearance.
For the winding of triangular connection, the appearance of the burn is the law of one phase burning two phases, and for the winding of star connection, the lack of phase is the law of two phases burning one phase. The root cause of the burning is due to the heat caused by too much current.
If there is a lack of phase during the operation of the motor, the speed of the motor will be slowed down instantly, and the phase current that is not in the phase winding will soon exceed the rated current of the motor, or even reach several times the rated current, resulting in the phase winding being seriously heated and burned due to the large current.
When the motor is fully loaded, the motor is in the overcurrent state that is, the current exceeds the rated current, the motor will change from fatigue to gridlock, and the line current in the unbroken phase will increase more, causing the motor winding to burn out quickly. The winding current of the unbroken phase increases rapidly when the light-carrying motor is broken, and the winding of the unbroken phase is burned out due to high temperature rise.
If the relationship between the load torque and electromagnetic torque of the motor is analyzed, the load torque and electromagnetic torque of the motor are relatively balanced during normal operation. When the motor is out of phase, the electromagnetic torque of the motor suddenly decreases. In order to meet the needs of load operation, the current of the motor winding will increase more, and the increase of current means that the winding will heat up. As a result, the insulating layer of the electromagnetic wire and other insulating materials of the phase winding deteriorate and are burned.
When the motor winding has the problem of phase deficiency, the fact that the insulation between phases and the insulation to the ground is burned often occurs at the same time. However, for relatively large motors, necessary monitoring and protection measures (such as differential protection) are often taken, and when the motor voltage or current is unbalanced, the protection device will cut off the power supply in time, effectively protecting the safety of the motor winding.
Post time: Jun-19-2024
