1. Low air gap between motor stator and rotor.
In general, the air gap in small or medium-type motors is between 0.2 and 1.5 mm. The wide air gap necessitates a significant excitation current, which impacts the motor's power factor. Moreover, a small air gap could result in friction or collisions with the rotor. The various axes of the frame, the end cover, and the rotor generally generate bore sweeping, which makes it easy for the motor to heat up or even burn down. This is because of the severe bearing out of tolerance as well as the wear and deformation of the inner hole of the end cover. In the event that a worn-out bearing is discovered, it must be replaced promptly, and the end cover must either be replaced or brush-plated. Inserting the end cover is the easier way to do this.
2. Material leakage into the motor causes it to become hotter and lose insulation.
The motor will sweep the bore until the insulation of the motor winding is worn away, at which point it will be damaged or scrapped. This happens when solid materials or dust enter the motor through the junction box and reach the air gap between the stator and rotor of the motor.
3. Motor will overheat if the voltage is too high.
An excessive voltage puts the motor's insulation in jeopardy, increasing the likelihood of a breakdown. An excessively low power supply voltage will result in a decrease in electromagnetic torque. A rise in slip will result in a motor overload and heating if the load torque is not decreased and the rotor speed is too low. The overload over time will shorten the motor's lifespan. The motor will overheat if the three-phase voltage is asymmetric, meaning that one phase's voltage is either too high or too low, resulting in an excessively high single-phase current.
4. Unusual vibration or noise may cause the motor to heat up.
If the pump is operating properly, the vibration may caused by the motor. The majority of vibration is brought on by the rotor's poor dynamic balance, a defective bearing, the shaft's bending, the rotor's and base's different shaft axes, the fasteners' looseness, or the uneven foundation of the motor installation. It can also be caused by the mechanical end transmission, you had better depend on the specific circumstances.
5. Caused by the motor running out of phase.
The lack of phase frequently results in the motor not starting at all, starting slowly, rotating powerlessly, the current rising and making a "buzzing" sound happen. When the load on the shaft does not change, the motor will enter a severe overload condition and the stator current will double or even triple the rated value. Therefore, the motor will heat up or maybe burn out quickly.
6. Motor becomes hot due to the bearing's poor performance.
To determine whether the bearing end temperature is within the normal range, you can either feel it with your hands or use a thermometer. If you hear an impact sound, one or more balls may have been crushed. There is not enough bearing oil if you hear the hissing sound. The grease should be changed in the motor once every 3000-5000 hours.
