We often use three phase motors in industrial applications and agricultural production, three-phase induction motor has various faults.
Among them, the three phase induction motors are running out of phase is a common fault of the electric motor.
Here we talk about what happens to the electric motor when it is out of phase and what causes it to be out of phase.
Missing one phase when starting three-phase motor
A three phase induction motor running out of phase means that the three phase motor stator winding is missing one phase of the three-phase power supply.
When the motor is missing one phase, if the induction motor is energized and started, the three phase motor will generally make a "buzzing" sound and the three phase ac motor speed will be slow.
When the three phase induction motor is dragging a heavy load, it can't reach the specified speed when starting or even can't start up.
If this state continues for a long time, the ac power motor will overheat due to the long time high current, and it will smoke and burn up seriously.
One phase is missing when the three phase motor is running
In the three phase ac motor running process, if suddenly missing a phase, then the three phase motors speed will be quickly reduced, then the motor stator windings current will also increase a lot, and at the same time will issue a "buzz" abnormal sound.
In this case the ac motor can not run for a long time, otherwise the three-phase motor will be burned.
We can use a jingle to remember the hazards of three-phase motor running out of phase, that is, "motor out of phase do not wait, early elimination of disaster can be avoided."
Three-phase motor is out of phase causes
The causes of three-phase motor out of phase can be generally summarized into:
Three-phase motor external and three-phase motor internal
Three-phase motor is out of phase external causes.
In a large number of maintenance cases is common in the motor junction box wiring screws loose; followed by loose or oxidation of the connection points in the three-phase power circuit, such as poor contact or contact resistance of some contractors and causing the power supply power shortage.
There is also a fuse operation in the fuse disconnected or not connected tightly, etc.
Three phase motor phase loss internal causes.
Internal causes are generally rare, usually the three-phase motor lead wire breakage.
At this time we can measure the DC resistance of the three-phase main winding.
If there is a phase resistance value is very large or infinity, then this winding is the broken phase.
If the resistance of the three phases is basically balanced, then the cause of the induction motors can be excluded.
Therefore, it is very harmful to the three phase motor to run out of phase, we can use some protection measures to protect the three-phase motor when it is out of phase.
For example, we can use thermal relays with phase breaking protection for phase breaking protection, for stator winding connected to Y type we can use two-pole or three-stage structure thermal relays for phase breaking protection.
If the stator winding of the motor is connected to a triangle, then we can only use a three-stage thermal relay with phase breaking protection so as to achieve phase breaking protection.
There are many information about the electric motors.
The above is my summary of some knowledge, if you have anything to add, welcome to leave a message in the comments section.
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