When the power supply voltage is too low, if the electromagnetic torque of the three-phase asynchronous motor remains unchanged, the magnetic flux will decrease, the rotor current will increase correspondingly, and the load power component in the stator current will increase accordingly, resulting in increased copper loss in the winding, resulting in overheating of the fixed and rotor windings. Here is a simple understanding with Senli Motor Xiaobian.
Too low a voltage can cause overheating, and too high a voltage,Three-phase asynchronous motorWill also produce-The heating problem will increase factors such as back electromotive force and magnetic flux density. Since the size of the iron loss is proportional to the square of the magnetic flux density, the iron loss increases, resulting in overheating of the core. The increase of magnetic flux causes a sharp increase in the component of excitation current, resulting in the increase of copper loss in the stator winding of three-phase asynchronous motor and overheating of the winding. Therefore, when the power voltage exceeds the rated voltage of the motor, the three-phase asynchronous motor will overheat.
When a phase of the power line is broken, a fuse is blown, or the Angle head of the knife starting equipment is burned to cause a phase failure, it is possible to cause the three-phase motor to go single-phase, resulting in the operation of the two-phase winding through the high current and overheating, and eventually burned. Therefore, fuse protection is generally not applicable to three-phase motors.
When the three-phase power supply is unbalanced, it will cause the three-phase current of the motor to be unbalanced, causing the winding to overheat.
It follows that whenThree-phase asynchronous motorWhen overheating, the cause of the power supply should be considered first (soft start, frequency converter, servo drive can be regarded as the power supply). After determining that there is no problem with the power supply, then consider other factors.
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