Common fault and solutions for tower crane

1. The air gap between the stator and rotor is very small, which is easy to lead to the collision between the stator and rotor.

In medium and small motors, the air gap is generally 0.2mm ~ 1.5mm. When the air gap is large, the excitation current is also large, consequently affects the power factor of the motor. If the air gap is too small, the rotor may occur the friction or collision.Generally, due to the serious out-of-tolerance of bearing and the inner hole of the end cover is out of shape caused by wearing, different axes of the machine base, end cover and rotor will scratch, which makes the motor hot even burn it out easily. If the bearing is wearing, it should be replaced timely , replacing or plating the end cover, a simple method is to inlay a sheath for the end cover.

2. The abnormal vibration or noise of the motor can easily cause the motor hot.

This circumstance is a kind of vibration caused by motor itself , which is usually caused by following reasons:

1) Dynamic balance of the rotor is not good;

2) The bearing is not good and the shaft is bending;

3) Axes of the machine base, end cover and rotor are different;

4) Fasteners are loose or installation foundation of the motor is out of flatness;

5) Vibration will caused noise and additional load.

Eliminate the problem according to specific circumstance.

3. The bearing is working abnormally

Whether the bearing works normally can be judged by the experience of hearing and temperature.The bearing end can be tested by hand or thermometer to judge whether the temperature is within the normal range. A copper bar may also be used to contact the bearing box, if a impact sound is heard, it indicates that one or more ball bearings have been crushed; if a sizzle is heard, it indicates that the lubricating oil of the bearing is not enough, the motor should be lubricated every 3,000 to 5,000 hours.

4. The power supply voltage is too high and the excitation current increasing caused the motor too hot

The insulation of the motor will be damaged even breakdown when the voltage is too high. When the voltage is too low, the electromagnetic torque will be greatly reduced, if the load torque is not reduced , the RPM of the rotor is too low, then the increase of slip speed will cause the motor overload and hot, and the long time overload will affect the working life of the motor.

In short, no matter the voltage is too high or too low the current will increase, the motor will be hot and damaged. Therefore, according to the national standard, the variation of the motor power supply voltage should not exceed ±5% of the rated value, and the motor output power can maintain the rated value. Motor supply voltage shall not exceed ±10% of the rated value, and the difference between three-phase supply voltage shall not exceed ±5% of the rated value.

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