Analysis of periodic maintenance of three-phase motors In order to reduce or avoid sudden damage to three-phase motors, regular maintenance and overhaul of three-phase asynchronous motors is very necessary. If the motor overheats and the stator winding insulation is too low, it must be repaired immediately. The maintenance method of the three-phase asynchronous motor is to disassemble the motor, clean the parts first, and then perform an apparent inspection on them to see if there is any abnormality. The dimensions of the critical parts are then measured and the motor windings are electrically inspected. The specific operations are as follows:
Sensor structure:
A lens collects light of a particular color, and a color filter filters light of other colors, projecting one color onto the area
Connection mode of Sensor and substrate:
COB: Module takes the sensor die and connects the sensor to the substrate through the gold wire.
CSP/TSF: Sensor is connected to the substrate and packaged when shipped.
IR Cut and Blue Galss:
The function of IR Cut is to filter out the light frequency invisible to human eyes (reflected back). What human eyes can see is 400~700nm.
Blue Glass absorbs infrared rays, which are not easy to be reflected internally
The Image circle of the Lens needs to cover the sensor's sensitive area
Lens shading:
A condition in which light is unevenly distributed, such as when the center is lit and the outside is dimmed. This is mainly because most of the light is concentrated in the middle, and because different wavelengths of light are imprinted in different places
FOV:
The lens Angle of the module must be the same as that of the lens; otherwise, when the lens Angle is too large, dark Angle may appear.
1, mechanical inspection
1 Check the outer casing and end cover of the motor for cracks. If there are cracks, weld and replace them.
2 Check the axial clearance of the rotor from one side to the other side. When measuring, insert a feeler gauge of 500~600mm long between the stator and the rotor, measure the air gap by 4 or 8 equally divided positions, and then take The average value. If the deviation between the average value and the reference value is large, check whether the shaft is bent and the assembly process is proper.
3 Move the rotor by hand to see if it can rotate. If you can't turn it to see if there is any foreign matter stuck, the bearing is good. Then replace the bearing and bushing according to the situation.
4 Measure and inspect the upper and lower outer stops of the impeller and the size of the inner ring and the inner diameter of the motor. Whether the two matching clearances are within the range specified by the inspection standard, replace the parts or take other measures when the tolerance is exceeded (such as : Surfacing, inserting) to meet the specified requirements.
5 Observe and check the appearance of the rotor and the rotor, especially pay attention to the abnormality of the weld.
2, electrical inspection
1 DC resistance check: The imbalance of the three-phase resistor must not exceed 2%.
2 Insulation resistance check: The insulation resistance of the three-phase asynchronous motor winding can generally reach more than 100MΩ. If it is lower than 5MΩ, it is necessary to analyze the cause, whether the insulation is damp, or the winding is grounded due to poor insulation. If there is no problem in the balance of the three-phase resistance by the bridge test, it is purely insulated and needs to be dried.
If the three-phase resistance of the stator is unbalanced, it is necessary to perform the ground pressure test and the inter-turn test on the three phases of the motor coil respectively to find the grounding point.
3. Final assembly and inspection test
1 After completing the repair of the stator and rotor, prepare the qualified bearings, bushings, seals, etc. for final assembly. 2 After the assembly is completed, the rotor should be rotated by hand. The rotation should be uniform and flexible. The rotor should have a certain amount of axial yaw. The turbulence should be within the range specified by the inspection standard: check the DC resistance and insulation resistance after finishing the assembly. After considering that the electrical performance is normal, the three-phase asynchronous motor is subjected to a withstand voltage test, and finally the test operation is performed to observe whether the current, the rotational speed, the vibration, and the like are abnormal.
4, restorative overhaul
A three-phase asynchronous motor with a damaged winding is subject to restorative overhaul.
2 The damage is generally caused by the grounding of the stator windings, the phase-to-phase breakdown, the short circuit between the turns of the coil, and the overloading of the windings. The stator coils need to be replaced.
3 stator winding replacement of more than 75kW of stator windings mostly use Class F insulation. Enameled wire, slot insulation, wedge, insulating sleeve, lead wire and impregnating varnish are all required to use Class F insulation.
Most of the stator windings below 475 kW are replaced with Class B insulation. Enameled wire, slot insulation, wedge, insulating sleeve, lead wire and impregnating varnish are all required to use Class B insulation.
5 The principle of motor winding replacement is: repair as it is, especially the number of turns of the coil can not be changed arbitrarily, the change of the number of turns will obviously affect the main performance of the motor, the wire diameter is only close to the original total area, the winding form and the coil span are also Do not change.
----- Editor-in-Chief: Dalan Oil Pump Motor 02-Procurement Consultant
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