Judgment of motor failure
First of all, it should be judged whether it is caused by mechanical or electrical reasons?
The method is: connect the power supply, there is an abnormal sound, cut off the power supply, if the abnormal sound still exists, it is a mechanical failure; otherwise, it is an electrical failure.
 
1. Abnormal sound caused by mechanical failure
When the agricultural motor is in normal operation, the mechanical noise should be a small "rustling" sound, there is no ups and downs, no metal friction sound, that is, the sound of the normal operation of the bearing. Common abnormal sounds caused by mechanical failures are as follows: 
1) The "hissing" sound is the sound of metal friction? Generally, it is caused by dry grinding of the bearing due to lack of oil, and the bearing should be disassembled to add grease.
2) The "creaking" sound is the sound produced by the irregular movement of the rollers in the bearing, which is related to the clearance of the bearing and the state of the grease. If the motor only has this sound without other abnormal phenomena, and this sound disappears immediately after adding grease, it is not a fault, and the motor can still be used.
3) The sound of "chirping, chirping" is the sound produced by the rollers or balls running. If there is no other noise, and the sound decreases or disappears after adding grease, it is generally not a fault, and the motor can continue to run.
4) There are two possibilities for the "dong dong" sound. One is that the acceleration torque loosens the cooperation between the rotor core and the shaft when the motor suddenly starts, stops, reverses braking and other speed changes. The second is the sound from the transmission mechanism, which may be caused by looseness between the coupling or the pulley and the shaft, or wear of the key or keyway.
5) The "chacha" sound is the noise caused by the motor sweeping.
6) The periodic "popping" sound is caused by the unevenness of the belt joint.


2. Abnormal sound caused by electrical failure
1) The stout "buzzing" sound and the howling sound of elephant cattle are mainly caused by current imbalance, because when the current is unbalanced, it will generate electromagnetic noise related to the load with twice the power supply frequency, which is the main reason for the burnt out of agricultural motors . In this case, stop the machine immediately, and put it into operation after troubleshooting.
2) "Hissing" or "cracking" discharge sound When the stator winding has a slight bad contact or leakage, there will be a slight "hissing" discharge sound, and a "cracking" discharge sound will occur when it is serious.
3) The sound of mosquitoes is caused by the binding of the end of the stator winding is not firm or the dipping paint is not good, the end of the entire stator winding does not form a solid whole, and some wires are caused by the vibration of individual wires under the action of electromagnetic force.
4) The sound of metal impact when starting, stopping and load changes is generally caused by loose stator and rotor cores.
5) Irregular frog calls are caused by air gaps or looseness inside the iron core.
6) Metal shaking sound The iron sheet at the end of the stator opens, and the opened silicon steel sheet vibrates to make a metal shaking sound.