Induction motor fault detection

Fault diagnosis and maintenance of induction motor
(1) the inspection and repair of the reason why the motor does not turn on the power supply
The motor does not turn into the power supply, there are the following reasons:
1) wiring error of control equipment;
2) the setting value of overcurrent relay is small;
3) the power supply is not connected, such as the fuse burning, the switch is faulty or the contact is bad, the lead wire is broken, etc.;
4) the connection between the power supply and the motor is faulty;
5 motor winding fault, such as phase short circuit, grounding, fault line, circuit breakers, etc.;
6) the winding rotor asynchronous motor starts the misoperation or the starting resistance is too small;
7) motor bearing fault, stuck;
8) the stator and rotor iron core should be rubbed (sweep) to increase the load;
9) the motor load is too large or the mechanical rotation part is stuck.
(2) motor overheat check and repair
Found that the normal operation of the motor overheating, there are the following reasons:
1) the power supply voltage suddenly becomes higher, and it is not consistent with the rated voltage of the motor nameplate;
2) the load of the motor is changed greatly, and the motor is in overload condition;
3, due to the failure of the bearing or the gap wear out, the shaft bending, the local overheating deformation of the iron core, the rotor axial movement and other reasons, so that the stator and rotor core sweep;
4. The dust enters into the motor and is adhered to the insulating surface and the cooling air duct is blocked, the cooling air duct is blocked, the motor is not ventilated well, the cooling effect is greatly reduced, and the motor is overheated;
5) motor cooling device failure, adjust the wind temperature device failure, causing the motor overheating;
6) single-phase operation of three-phase motor;
7) the winding has faults, such as short circuit, open circuit, grounding, fault and so on;
8) uneven air gap.
The motor rewind after the occurrence of overheating, the reason is:
1) wiring error;
2) coil turns too much or too little;
3) coil wire winding pitch is too small, too small or too large;
4) the motor assembly quality is not good, the core is not aligned, the rotor stator axial gap caused by axial magnetic pull, air gap assembly and adjustment is not uniform.
Due to the continuous improvement of the motor insulation level, allowing the temperature rise limit also increased, so the higher the temperature rise of the motor casing may be normal. But the alcohol thermometer testing department shell temperature and the temperature of bearings, and allow the insulation level of the motor temperature rise compared to confirm after the motor is overheated, then can be checked according to the following steps.
1) first check whether the three-phase power supply voltage is balanced, the degree of voltage fluctuation is greater than the manufacturer's guarantee (+ 10[%]). Due to the unbalanced voltage, three-phase unbalanced current is generated, which leads to the loss of the motor and the heating of the motor. Power frequency changes (+ 5[%]) motor heating also has an impact, but the actual change is not large, so in the analysis of the general can not be considered.
2) check whether the operation of the motor Dan Xiang, three-phase contactor contact is good, the switch is a fuse fuse, wiring is not (Dan Xiang) off. Fault check out after processing.
3) check whether the three-phase current exceeds the rated value. If exceed the rated value, check the reason. When dealing with this kind of fault, we should find out the cause of the sweep of the bore: the bending of the shaft. A slight iron core sweep does not affect the normal operation of the motor, sweeping the hole is serious, the rotor can be used to cut a layer of the rotor surface (general turning diameter is about 0.2mm).
4) the influence of the dust accumulation on the heat dissipation of the motor, the blockage of the filter screen, the blockage of the ventilation duct and the ventilation pipe, etc., will cause the motor to overheat. Therefore, we can take measures to eliminate dust blowing, if necessary, the motor to be broken for cleaning.
5 if the winding is faulty, it can be used to test the short circuit and grounding of the winding. According to the experience shows that the motor windings, such as inter turn short circuit, the motor will vibrate, moving a lot of time will not be long time will smoke. However, the inter turn short circuit causes the motor to generate heat, and the opportunity for a long period of time is very small.The motor temperature rise rewound after overhaul may be overrun, treatment is not well insulated, the coil data is not caused by wrong connection and assembly quality, etc.. At this time, the motor should be broken down to check the original records and find out the correctness of the winding data.