1. The demolition method must be correct and precise. Before starting the disassembly, use a pair of tweezers to mark the gap between the front and rear cover and the base. Since the motor is assembled quite reasonably at the factory, if it's not reassembled properly after repair, it may cause slight misalignment, leading to reduced shaft flexibility. When disassembling, carefully observe the degree of winding burnout and try to identify the root cause. Pay attention to issues such as minor brush wear or broken bearings. If rust is severe, avoid forceful removal; instead, use gas welding to heat the joint gently and tap lightly with a hammer. Utilize the principle of thermal expansion to remove the components smoothly.
When dismantling a damaged winding, be cautious to protect the core and the plastic retainer. An improper method can cause the iron core to become damaged. When the motor is energized, electromagnetic effects may occur, causing vibration in the core and the winding itself, which can lead to insulation damage of the insulating paper and the wire. To remove the winding, use diagonal pliers to cut one end, and then use regular pliers for the other end.
2. The self-made coil mold should be appropriately sized and well-designed. Ensure that when inserting the phases, the ends form a "triple plane" shape, and secure the ends firmly to prevent any scratches during assembly.
3. Adjusting the position of the "position screw" requires careful attention. Ensure the rotor rotates freely and the no-load current is optimal. Once adjusted, tighten the locking nut securely.
4. Proper waterproof insulation of joints is essential. Strip the sheath and insulation layer, remove the lacquer and oxide layers from the copper wire, and solder the connection. After soldering, smooth out any sharp edges, burrs, and excess solder. Apply a 6-layer semi-overlapping polyethylene tape, followed by a 2-layer polyester tape for mechanical protection.
5. Insulation painting of submersible pump motor coils should be done correctly. After shaping the stator, immerse the entire unit in insulating paint and let it sit for 0.5 hours. Some repair shops use brushes, but this method often leads to uneven coverage due to the paint’s viscosity. Immersion ensures better penetration and uniformity, meeting quality standards.
6. The baking time and temperature for the stator must be appropriate. Baking removes moisture and dries the insulating paint. The correct procedure is to place the stator in an oven and gradually increase the temperature to 110–120°C, keeping it warm for 12 hours, then cooling it inside the oven for another 12 hours. Some shops use lower temperatures (60–80°C) for only 4–6 hours, or skip the heating process entirely, leading to moisture retention and poor motor performance.
7. When adding mechanical oil, ensure its quality is high. After repairing an oil-immersed motor, fill all gaps in the stator and rotor with new No. 5 or No. 10 mechanical oil. Avoid mixing old and new oils, as this can reduce oil quality and affect future motor performance.
8. The insulation resistance between the winding and the housing must meet specifications. Use a 500V voltmeter to measure the cold insulation resistance after filling the stator with oil. It should be at least 100 MΩ. However, many repaired motors fail to meet this standard, especially in wet conditions. Low insulation resistance can cause electric shocks and must be addressed immediately.
9. The integral sealed box must be inspected and maintained regularly. This component is critical for the submersible pump’s operation. After running 5MΩ, inspect the box by applying a small amount of oil through the filler hole on the lower end cap. If the water content in the oil is less than 5 ml, the seal is intact. Check monthly. If water exceeds 5 ml after 50 hours, drain the oil, refill it, and check again after another 50 hours. If the water content remains low, continue using it. If it increases, there is a leak—check the grinding blocks or rubber seals and replace them if necessary.
For a sealed box being replaced, perform an air pressure test to check for leaks. If a leak is found, reassemble or replace the seal and dry the motor. Finally, top up the oil from both upper and lower filler holes.
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