How to self check the generator set fault?
2021-12-17
1、 Look
Observe whether there is any abnormality during the operation of the motor, which is mainly manifested in the following situations:
1. When the stator winding is short circuited, the motor may smoke;
2. When the motor runs under severe overload or phase loss, the speed will slow down and there will be a heavy "buzzing" sound;
3. When the motor maintenance network operates normally, but suddenly stops, sparks will be seen at the loose part of the wiring; The fuse is blown or a part is stuck;
4. If the motor vibrates violently, it may be that the transmission device is stuck, the motor is poorly fixed, the foot bolt is loose, etc;
5. If there are discoloration, burn marks and smoke marks at the internal contact and connection of the motor, it indicates that there may be local overheating, poor contact at the conductor connection or winding burning, etc.
2、 Listen
The motor shall emit uniform and light "buzzing" sound without noise and special sound during normal operation. If the noise is too loud, including electromagnetic noise, bearing noise, ventilation noise, mechanical friction sound, etc., it may be a fault precursor or fault phenomenon.
1. For electromagnetic noise, if the motor makes a loud and heavy sound, the reasons may be as follows:
(1) The air gap between the stator and the rotor is uneven. At this time, the sound is high and low, and the interval between high and low sounds remains unchanged, which is caused by bearing wear, resulting in the non concentricity of the stator and the rotor;
(2) The three-phase current is unbalanced. This is due to wrong grounding, short circuit or poor contact of three-phase winding. If the sound is very dull, it indicates that the motor is seriously overloaded or out of phase operation;
(3) Loose iron core. During the operation of the motor, the fixing bolts of the iron core are loosened due to vibration, resulting in the loosening of the silicon steel sheet of the iron core and noise.
2. Bearing noise shall be monitored frequently during motor operation. The monitoring method is: push one end of the screwdriver against the bearing installation part and the other end close to the ear to hear the running sound of the bearing. If the bearing operates normally, its sound is a continuous and small "rustle" sound, and there will be no change from high to low and metal friction sound. The following sounds are abnormal:
(1) There is a "squeak" sound when the bearing is running, which is the sound of metal friction. It is generally caused by the lack of oil in the bearing. The bearing should be disassembled and filled with an appropriate amount of grease;
(2) If there is a "pumping" sound, it is the sound made when the ball rotates. It is generally caused by dry grease or lack of oil. An appropriate amount of grease can be added;
(3) If there is a "click" or "creak" sound, it is the sound generated by the irregular movement of the ball in the bearing, which is caused by the damage of the ball in the bearing or the drying of the lubricating grease after the motor is not used for a long time.
3. If the transmission mechanism and driven mechanism make continuous sound instead of high and low, it can be handled in the following situations:
(1) The periodic "snap" sound is caused by the unsmooth belt joint;
(2) The periodic "thump" sound is caused by the looseness between the coupling or pulley and the shaft and the wear of the key or keyway;
(3) The uneven collision sound is caused by the blade colliding with the fan cover.
3、 Smell
Faults can also be judged and prevented by smelling the smell of the motor. Open the junction box and sniff. Check whether there is burnt smell. If there is special paint smell, it indicates that the internal temperature of the motor is too high; If heavy paste smell or burnt smell is found, the insulation maintenance network may be broken down or the winding has been burned. If there is no smell, it is also necessary to measure the insulation resistance between the winding and the shell with a megohmmeter, which is lower than 0.5 trillion, and it must be dried. If the resistance value is zero, it indicates that it has been damaged.
4、 Touch
Touching the temperature of some parts of the motor can also judge the cause of the fault. In order to ensure safety, the back of your hand shall be used to touch the motor shell and the parts around the bearing. If the temperature is abnormal, the reasons may be as follows:
1. Poor ventilation. Such as fan falling off, ventilation duct blockage, etc;
2. Overload. Cause excessive current to overheat the stator winding;
3. Inter turn short circuit of stator winding or three-phase current imbalance.
4. Frequently start or brake;
5. If the temperature around the bearing is too high, it may be caused by bearing damage or lack of oil.
Observe whether there is any abnormality during the operation of the motor, which is mainly manifested in the following situations:
1. When the stator winding is short circuited, the motor may smoke;
2. When the motor runs under severe overload or phase loss, the speed will slow down and there will be a heavy "buzzing" sound;
3. When the motor maintenance network operates normally, but suddenly stops, sparks will be seen at the loose part of the wiring; The fuse is blown or a part is stuck;
4. If the motor vibrates violently, it may be that the transmission device is stuck, the motor is poorly fixed, the foot bolt is loose, etc;
5. If there are discoloration, burn marks and smoke marks at the internal contact and connection of the motor, it indicates that there may be local overheating, poor contact at the conductor connection or winding burning, etc.
2、 Listen
The motor shall emit uniform and light "buzzing" sound without noise and special sound during normal operation. If the noise is too loud, including electromagnetic noise, bearing noise, ventilation noise, mechanical friction sound, etc., it may be a fault precursor or fault phenomenon.
1. For electromagnetic noise, if the motor makes a loud and heavy sound, the reasons may be as follows:
(1) The air gap between the stator and the rotor is uneven. At this time, the sound is high and low, and the interval between high and low sounds remains unchanged, which is caused by bearing wear, resulting in the non concentricity of the stator and the rotor;
(2) The three-phase current is unbalanced. This is due to wrong grounding, short circuit or poor contact of three-phase winding. If the sound is very dull, it indicates that the motor is seriously overloaded or out of phase operation;
(3) Loose iron core. During the operation of the motor, the fixing bolts of the iron core are loosened due to vibration, resulting in the loosening of the silicon steel sheet of the iron core and noise.
2. Bearing noise shall be monitored frequently during motor operation. The monitoring method is: push one end of the screwdriver against the bearing installation part and the other end close to the ear to hear the running sound of the bearing. If the bearing operates normally, its sound is a continuous and small "rustle" sound, and there will be no change from high to low and metal friction sound. The following sounds are abnormal:
(1) There is a "squeak" sound when the bearing is running, which is the sound of metal friction. It is generally caused by the lack of oil in the bearing. The bearing should be disassembled and filled with an appropriate amount of grease;
(2) If there is a "pumping" sound, it is the sound made when the ball rotates. It is generally caused by dry grease or lack of oil. An appropriate amount of grease can be added;
(3) If there is a "click" or "creak" sound, it is the sound generated by the irregular movement of the ball in the bearing, which is caused by the damage of the ball in the bearing or the drying of the lubricating grease after the motor is not used for a long time.
3. If the transmission mechanism and driven mechanism make continuous sound instead of high and low, it can be handled in the following situations:
(1) The periodic "snap" sound is caused by the unsmooth belt joint;
(2) The periodic "thump" sound is caused by the looseness between the coupling or pulley and the shaft and the wear of the key or keyway;
(3) The uneven collision sound is caused by the blade colliding with the fan cover.
3、 Smell
Faults can also be judged and prevented by smelling the smell of the motor. Open the junction box and sniff. Check whether there is burnt smell. If there is special paint smell, it indicates that the internal temperature of the motor is too high; If heavy paste smell or burnt smell is found, the insulation maintenance network may be broken down or the winding has been burned. If there is no smell, it is also necessary to measure the insulation resistance between the winding and the shell with a megohmmeter, which is lower than 0.5 trillion, and it must be dried. If the resistance value is zero, it indicates that it has been damaged.
4、 Touch
Touching the temperature of some parts of the motor can also judge the cause of the fault. In order to ensure safety, the back of your hand shall be used to touch the motor shell and the parts around the bearing. If the temperature is abnormal, the reasons may be as follows:
1. Poor ventilation. Such as fan falling off, ventilation duct blockage, etc;
2. Overload. Cause excessive current to overheat the stator winding;
3. Inter turn short circuit of stator winding or three-phase current imbalance.
4. Frequently start or brake;
5. If the temperature around the bearing is too high, it may be caused by bearing damage or lack of oil.