Partial burnout of three phase asynchronous motor?

Because the starting current of the three-phase asynchronous motor is 4 7 times of the rated current, the current at the start is large, however, the phenomenon that the motor is burned out because of the large starting current is relatively rare, one is because the motor has undergone many starting experiments when leaving the factory.

If the voltage is too high, the stator magnetic flux of the motor will be close to saturation, and the current will increase sharply, and the efficiency of the motor will decrease and the heat will be seriously generated. When the voltage is too low, the speed of the motor decreases, the heat dissipation of the fan decreases and heats up, and the motor is easy to burn if there is a stalled rotor phenomenon. If the voltage is too low, the three-phase asynchronous motor will be burned; 1) The excitation current of the motor is not simply obtained by dividing the voltage by the resistance, the motor winding is an inductance, and there is mutual inductance when the motor rotates, and the excitation current of the motor mainly depends on the inductive reactance under the influence of mutual inductance.

2) The voltage affects the level of the magnetic potential established by the motor. 3) The heat dissipation of the motor is designed according to the rated speed. 4) When the voltage is low, the speed decreases, and the heat dissipation efficiency decreases, and 5) the inductive reactance decreases, and the current increases (such as extreme cases:

The motor starting current is equivalent to the short-circuit current), and the temperature rises. 6) Accumulate heat and burn the motor.

Because the voltage is low, the current frequency must be low, and the low-frequency current causes the coil eddy current to be enhanced, seriously heated, and eventually burned

What is the cause of the burning of the 2-phase winding of the three-phase asynchronous motor triangular motor? Hello dear, reasons: 1. If the one-phase or two-phase winding of the motor burns out (or overheats), it is generally caused by the lack of phase operation.

I will not make a profound theoretical analysis here, but only give a brief explanation. When the motor is out of phase for any reason, although the motor can continue to run, but the speed decreases, the slip becomes larger, wherein B, C two phases become a series relationship and parallel with phase A, under the condition of constant load, phase A current is too large, long-term operation, the phase winding must be overheated and burned. After the power supply is out of phase, the motor can still continue to run, but the same speed decreases significantly, the slip becomes larger, and the rate of the magnetic field cutting the conductor increases, then the B phase winding is opened, and the A and C two-phase windings become series and the passing current is too large, and the long-term operation will cause the two-phase winding to burn out at the same time.

2. It is necessary to point out here that if the stopped motor lacks a one-phase power supply to close, it will generally only hum and cannot start, because the motor will produce a circular rotating magnetic field in the stator core through symmetrical three-phase alternating current, but when the one-phase power supply is missing, the single-phase pulsating magnetic field generated in the stator core cannot make the motor produce starting torque. Therefore, the motor cannot be started when the power supply is out of phase. However, in operation, the air gap of the motor is generated by the elliptical rotating magnetic field with a high three-phase harmonic composition, so the motor in operation can still run after the lack of phase, but the magnetic field is distorted, and the harmful current component increases sharply, which eventually leads to the burning of the winding.

3. Corresponding countermeasures: whether the motor is static or dynamic, the direct harm caused by the lack of phase operation is the overheating or even burnout of the one-phase or two-phase winding of the motor. At the same time, the insulation aging is accelerated due to the overcurrent operation of the power cable.

The extraordinary thing is that when it is static, the lack of phase will produce a stalled current in the motor winding that is several times the rated current. The speed at which the windings burn out is faster and more serious than the sudden loss of phase during operation. Therefore, while we carry out routine maintenance and overhaul of the motor, we must carry out a comprehensive overhaul and test of the corresponding MCC functional unit of the motor.

The three-phase motor suddenly lacks phase in operation, the motor will also choose, but the speed will slow down, the motor sound will be abnormal, and it will burn out in a few minutes, the lack of phase is that the three-phase power supply suddenly drops a phase, and one of the three windings of the motor suddenly has no voltage, and the current of the other two windings increases, and the coil is heated and burned, not a short circuit.

One of the three-phase circuits of a brushless motor or brushless controller cannot work. Phase loss is divided into main phase absence and Hall phase loss. It is manifested as the motor shaking and cannot work, or the rotation is weak and noisy. It is easy for the controller to burn out when it works in a phase-out state.