Correct safety protection of submersible sewage pumps
Submersible sewage pumps often cause motor windings to burn out due to lack of water in the pool.
1. It is forbidden to start the machine if the power supply voltage is abnormal.
Because low-voltage power supply lines are relatively long, it is common for the voltage at the end of the line to be too low. When the phase voltage is lower than 198 volts and the line voltage is lower than 342 volts, the submersible pump motor speed decreases and cannot reach 70% of the rated speed. It will cause the starting winding to be energized for a long time and generate heat or even burn out the winding and capacitor. On the contrary, excessive voltage causes the motor to overheat and burn out the windings. Therefore, when the submersible pump is in operation, the operator must observe the power supply voltage at any time. If it is less than 10% lower than the rated voltage and more than 10% higher than the rated voltage, the motor should be stopped to find out the cause and eliminate the fault.
2. Confirm the correct direction of motor rotation
The direction of rotation of the motor should be clarified. There are many types of high-lift submersible pumps that can discharge water during forward and reverse rotation. However, the water output is small and the current is large during reverse rotation. If the reversal time is long, the motor windings will be damaged.
3. Cable installation and insulation resistance requirements of submersible pumps
When installing a submersible pump, the cables should be overhead and the power cord should not be too long. Do not put force on the cable when the submersible pump is launched into the water or lifted out to avoid breaking the power cord. Do not sink into the mud when the submersible pump is working, otherwise it will cause poor heat dissipation of the motor and burn the motor windings. When installed, the insulation resistance of the motor should not be less than 0.5 megohms.
4. Avoid frequent switching
Do not switch the submersible pump on and off frequently. This is because backflow will occur when the electric pump stops. If it is started immediately, the motor load will start, resulting in excessive starting current and burning out the windings. Due to the large current at start-up, frequent starts will also burn out the submersible pump motor windings.
5. Installation of leakage protector
The leakage protector is also called a life-saving device. Its function can be understood from the three words "life-saving device". Because the submersible pump works underwater, it is easy to leak electricity, cause power loss and even cause electric shock. If a leakage protector is installed, as long as the leakage value of the submersible pump exceeds the operating current value of the leakage protector (generally no more than 30 mA), the leakage protector will cut off the power supply of the submersible pump to ensure safety and avoid leakage and waste of electrical energy.
6. It is prohibited to overload the submersible pump for a long time.
To prevent the submersible pump from being overloaded for a long time, do not pump water with a high sand content and observe whether the current value is within the value specified on the nameplate at any time. If the current is found to be too large, stop the pump for inspection. In addition, the dehydration operation time of the electric pump should not be too long to avoid overheating and burning the motor.
7. Pay attention to daily maintenance
Check the motor frequently. If you find cracks in the lower cover, damaged or failed rubber sealing ring, etc., you should replace or repair them in time to prevent water from penetrating into the machine.
8. Try to avoid starting the machine at low voltage
The power supply voltage differs by 10% from the rated voltage. If the voltage is too high, the motor will overheat and burn out the windings. If the voltage is too low, the motor speed will decrease. If it does not reach 70% of the rated speed, the starting centrifugal switch will close, causing the starting winding to become long. When energized for a long time, it will generate heat and even burn out the windings and capacitors. Because the electric pump will generate backflow when it stops, if it is started immediately, the motor load will start, causing the starting current to be too large and burning the winding.
