Overheating of
Submersible pump motors is one of the common faults, which may lead to decreased efficiency, equipment damage, and even safety accidents. This article starts from technical principles, analyzes in detail the six core causes of motor overheating, and provides targeted solutions and preventive measures to help users quickly locate problems and reduce maintenance costs.
1、 6 common reasons for overheating of submersible pump motors
1. Overload operation
Performance: The current exceeds the rated value, the temperature of the motor casing rises sharply, and the operating sound is abnormal.
Reason: The head and flow parameters do not match (such as the actual head far exceeding the rated value), or the viscosity and density of the medium are abnormal, leading to an increase in resistance. For example, when pumping mud, if the medium density exceeds 1.3 (water is 1.0), the motor needs to bear a greater load.
Solution: Re calculate the operating parameters and replace the compatible model; Regularly check the characteristics of the medium to avoid overload operation.
2. Power supply issues
Performance: Large voltage fluctuations, unstable motor speed, and difficulty starting.
Reason: Low voltage (more than 10% below rated value) or three-phase imbalance (voltage difference exceeding 5%). Phase loss operation can cause a surge in current, leading to overheating.
Solution: Install a voltage regulator or regulator; Check if the cable diameter matches to avoid voltage drop caused by long-distance power transmission; Install phase loss protection device.
3. Poor heat dissipation
Performance: The surface temperature of the motor exceeds 65 ℃ (ambient temperature+temperature rise exceeds the standard value).
Reason: Insufficient diving depth (motor not fully submerged), insufficient cooling water flow, and blocked cooling chamber. For example, when the motor casing is exposed to more than 50% of the water surface, the heat dissipation efficiency decreases by more than 50%.
Solution: Ensure that the diving depth is ≥ 0.5 meters; Clean the inlet filter and check the cooling circulation system; Install a liquid level sensor to prevent the motor from running dry.
4. Mechanical failure
Performance: Increased vibration, abnormal bearing noise, and damage to the insulation layer of the winding.
Reason: Bearing wear, rotor eccentricity, impeller jamming. Insufficient lubrication of bearings or deterioration of lubricating grease can increase friction and generate additional heat.
Solution: Regularly replace bearings (recommended every 1-2 years); Calibrate rotor dynamic balance; Check whether the impeller is entangled with debris and clean the accumulated sediment inside the pump body.
5. Insulation aging
Performance: Decrease in insulation resistance (below 0.5M Ω), tripping of leakage protector, and electrification of motor casing.
Reason: Long term high temperature operation and humid environment lead to deterioration of insulation materials. For example, after the motor winding becomes damp, the insulation resistance may decrease to below 0.1M Ω.
Solution: Use F-class or H-class insulated motors; Regularly check the insulation resistance and replace aging motors in a timely manner; Vacuum coating treatment is applied to the winding to enhance its insulation performance.
6. Winding fault
Performance: Burning smell, smoking, and short circuit in the winding.
Reason: Overload operation, frequent start stop, and water ingress caused the winding to become damp. Short circuit between windings can cause local high temperature and even burn out the motor.
Solution: Optimize the start stop logic (avoid frequent switching); Use motors with better waterproof performance (such as IP68 protection level); Immerse the winding to enhance insulation and install overload protectors.
2、 Prevention and maintenance strategies for overheating of submersible pump motors
Scientific selection
Select the matching model based on actual working conditions (head, flow rate, medium characteristics) to avoid "small horses pulling large trucks" or "overusing talents". For example, high viscosity media require the use of screw pumps or high-power submersible pumps.
Daily inspection
Temperature monitoring: Regularly detect the surface temperature of the motor using an infrared thermometer, with a focus on the winding temperature (which should be below 90 ℃).
Vibration detection: Monitor the stability of motor operation through vibration sensors, and stop the machine for inspection when the vibration value exceeds 7.1mm/s.
Current detection: Install an ammeter to ensure that the operating current is within ± 5% of the rated value.
Environmental optimization
Ensure that the installation environment of the submersible pump is well ventilated and avoid direct sunlight or high temperature baking. For example, in high-temperature environments, for every 10 ℃ increase in motor temperature, the lifespan is reduced by 50%.
Regularly clean the surface sediment of the motor to prevent blockage of the heat dissipation fins.
intelligent control
Introducing a variable frequency drive (VFD) to achieve soft start and reduce start stop impact. For example, variable frequency starting can reduce the starting current to less than 1.5 times the rated value.
Install temperature sensors and PLC control systems to achieve automatic shutdown protection against
overheating.
regular maintenance
Bearing maintenance: Check the lubrication condition of the bearings every 6 months and replenish or replace lubricating grease.
Sealing inspection: Check the mechanical seal or packing seal every quarter to prevent water leakage and moisture damage to the winding.
Insulation testing: Use a megohmmeter to test the insulation resistance annually to ensure it is ≥ 0.5M Ω.
3、 Typical Case Analysis
Case 1: Overheating of motor in agricultural irrigation pump station
Problem: The user reported that the temperature of the motor casing of the submersible pump reached 80 ℃ after running for 30 minutes.
Investigation: On site inspection found that the actual head was 45 meters, while the rated head of the motor was 30 meters, resulting in overload operation.
Solution: Replace the submersible pump with a head of 50 meters and install a voltage regulator to stabilize the voltage.
Case 2: Insulation aging of chemical sewage pumps
Problem: The motor trips frequently, and the insulation resistance detection value is 0.2M Ω.
Investigation: The medium is a highly corrosive liquid, and the insufficient protection level of the motor casing has caused the winding to become damp.
Solution: Replace the submersible pump with a fully stainless steel material and IP68 protection level, and impregnate the winding with epoxy resin.
4、 Summary
Overheating of submersible pump motors is the result of multiple factors working together, and it needs to be controlled throughout the entire process of selection, installation, operation, and maintenance. Through scientific selection, regular testing, intelligent control, and preventive maintenance, the risk of motor overheating can be significantly reduced, and the service life of equipment can be extended.
