What to do if the motor is hot?
As an indispensable and important power provider in people's production and life, many motors will generate severe heat during use, but they often do n’t know how to solve them, and even more seriously do not know why The heat generated by the motor should be grasped first in the use of the motor.
Let's take a look at the common reasons why the motor is very hot.
1
The air gap between the stator and the rotor of the motor is very small, which easily leads to collision between the stator and the rotor.
In medium and small motors, the air gap is generally 0.2mm to 1.5mm. When the air gap is large, a large excitation current is required, which affects the power factor of the motor; if the air gap is too small, the rotor may be subject to friction or collision. Generally, due to the severe bearing misalignment and the wear and deformation of the inner holes of the end cover, the different shaft centers of the machine base, end cover and rotor cause sweeping, which can easily cause the motor to heat up or even burn. If the bearing is found to be worn, it should be replaced in time, and the end cap should be replaced or brushed. The simpler method is to insert a sleeve into the end cap.
2
The abnormal vibration or noise of the motor easily causes the motor to heat up
This situation belongs to the vibration caused by the motor itself, most of which are due to the poor dynamic balance of the rotor, as well as poor bearings, curved shafts, different shaft centers of the end caps, bases, and rotors, loose fasteners, or uneven installation foundations of the motors and incomplete installation. The cause may also be transmitted from the mechanical end, which should be excluded according to the specific situation.
3
The abnormal operation of the bearing will definitely cause the motor to heat up. Whether the bearing works normally can be judged by hearing and temperature experience.
Use the hand or a thermometer to check the bearing end to determine whether the temperature is within the normal range. You can also use a listening rod (copper rod) to contact the bearing box. If you hear an impact sound, it means that one or more balls may be crushed. A snoring sound means that the bearing has insufficient lubricant. The motor should be changed once every 3,000 to 5,000 hours.
4
If the power supply voltage is too high, the excitation current will increase, and the motor will overheat.
Excessive voltage can jeopardize the insulation of the motor and risk of breakdown. When the power supply voltage is too low, the electromagnetic torque will be reduced. If the load torque is not reduced, the number of rotor revolutions will be too low. At this time, the increased slip rate will cause the motor to overload and generate heat. Long-term overload will affect the life of the motor. When the three-phase voltage is not symmetrical, that is, when the voltage of one phase is too high or too low, the current of one phase will be too large, and the motor will heat up. At the same time, the "torque" will be emitted when the torque is reduced. The winding will be damaged for a long time.
In short, no matter the voltage is too high, too low, or the voltage is asymmetric, the current will increase, and the motor will heat up and damage the motor. Therefore, according to national standards, the change of the motor power voltage should not exceed ± 5% of the rated value, and the output power of the motor can maintain the rated value. The motor power voltage must not exceed ± 10% of the rated value, and the difference between the three-phase power voltages should not exceed ± 5% of the rated value.
