1. The air gap between the stator and the rotor of the motor is very small, easily causing the stator and rotor to collide with each other.

In medium and small motors, the air gap is generally 0.2mm to 1.5mm. When the air gap is large, the excitation current is required to affect the power factor of the motor. If the air gap is too small, the rotor may be subject to friction or impact. In general, the bearing is seriously out of tolerance and the inner hole of the end cap is worn out and deformed, so that the three axes of the base, the end cap and the rotor cause a broom, which easily causes the motor to heat or even burn. If it is found that the bearing wear should be promptly replaced, the end cap should be replaced or brush plated. A simpler method of treatment is to cap the end cap.

2. The abnormal vibration or noise of the motor may cause the motor to heat up

This kind of situation belongs to the vibration caused by the motor itself, mostly due to the poor rotor dynamic balance, poor bearing, bending of the shaft, different shafts of the end cover, frame, and rotor, loose fasteners, uneven foundation for motor installation, and improper installation. Caused by the mechanical end may also be transmitted over, should be ruled out for specific circumstances.

3. The bearing is not working properly

Inevitably, the normal operation of the motor heating bearing can be judged by hearing and temperature experience. The bearing end can be detected by hand or thermometer to judge whether the temperature is within the normal range; the hearing box (copper rod) can also be used to contact the bearing box. If you hear the impact sound, it means that there may be one or more balls crushing, if you hear The buzzing sound means that the bearing has insufficient lubricating oil, and the motor should be replaced with grease for about 3,000 hours to 5,000 hours of operation.

4. The power supply voltage is high, the excitation current increases, the motor will overheat

Excessive voltage can jeopardize the insulation of the motor and cause it to break down. When the power supply voltage is too low, the electromagnetic torque will be reduced. If the load torque is not reduced, the rotor speed is too low. At this time, the increase in the slip rate will cause the motor to overload and heat, and the long-term overload will affect the life of the motor. When the three-phase voltage is asymmetrical, that is, if one phase voltage is too high or too low, it will cause the current of a certain phase to be too large and the motor will generate heat. At the same time, the reduction of the torque will produce a “click” sound, and a long time will damage the winding.

In short, whether the voltage is too high, too low, or the voltage is not symmetrical, the current will increase, causing the motor to heat up and damage the motor. Therefore, according to national standards, the change of the motor power supply voltage should not exceed ±5% of the rated value, and the motor output power can maintain the rated value. The motor supply voltage must not exceed ±10% of the rated value. The difference between the three-phase supply voltages should not exceed ±5% of the rated value.

5. Short circuit of winding, short circuit between windings, short circuit between phases and open circuit of winding

After the insulation damage between the adjacent two wires in the winding, the two conductors collide with each other, which is called a winding short circuit. A winding short circuit that occurs in the same winding is referred to as a turn-to-turn short circuit. A winding short circuit that occurs between two phase windings is called an interphase short circuit. Either way, it will increase the current of one phase or two phases, cause local heating, and cause insulation aging to damage the motor. Breaking of the winding means that the stator or rotor windings of the motor are broken or blown. Whether the winding is short-circuited or open circuit may cause the motor to heat or even burn. Therefore, after this happens, it must be stopped immediately.

6. The material leaks into the motor to reduce the insulation of the motor, so that the temperature of the motor can be reduced.

Solid material or dust entering the motor from the junction box will reach the air gap between the stator and rotor of the motor, causing the motor to sweep, until the motor winding insulation is worn out, causing the motor to be damaged or scrapped. If the liquid and gas media leak into the motor, it will directly cause the motor insulation to drop and trip.

General liquid and gas leaks have the following manifestations:

(1) Leakage of various containers and delivery pipes, seal leakage of pump body, flushing equipment, and ground.

(2) After the mechanical oil leaks, enter the motor from the gap in the front bearing box.

(3) Wear of oil seals, such as speed reducers connected to the motor, enters the motor shaft along with the mechanical lubrication oil. Dissolve the motor insulation paint after it accumulates inside the motor, and gradually reduce the insulation performance of the motor.

7. Almost half of the motors burned out due to the lack of motor operation

The lack of phase often causes the motor to be inoperable or the speed is slow after start-up, or there is a “click” noise phenomenon when the rotating no-load current increases. If the load on the shaft does not change, the motor is in a severe overload condition and the stator current will reach 2 times or more of the rated value. In a short time, the motor will heat up and even burn.

The main reasons for the lack of operation are as follows:

(1) The power line is disconnected due to the failure of other equipment, and the other three-phase equipment connected to the line will run out of phase.

(2) One phase of the circuit breaker or contactor causes phase loss due to burnout or poor contact of the bias voltage.

(3) The lack of phase due to aging, wear, etc.

(4) One phase winding of the motor is open circuited, or one phase connector in the junction box is loose.

8. Other non-mechanical electrical fault causes

The temperature of the motor caused by other non-mechanical electrical faults may cause serious motor failure. If the ambient temperature is high, the motor lacks a fan, the fan is incomplete, or the fan cover is missing. In this case, cooling must be forced to ensure ventilation or replacement of the fan blades. Otherwise, the normal operation of the motor cannot be guaranteed.

To sum up, in order to be able to use the correct method for motor fault handling, we must be familiar with the characteristics and causes of common motor faults, seize the key factors, and regularly check and maintain. In this way, you can avoid detours, save time, eliminate faults as quickly as possible, and keep the motor in normal operation. In order to ensure the normal production of the workshop.