Submersible pump is an important equipment for water extraction in deep wells. When in use, the whole unit works in the water and extracts the groundwater to the surface. It is used for domestic water, mine rescue, industrial cooling, farmland irrigation, seawater lifting, ship load regulation, and fountain landscape. Hot water submersible pump is used for bathing in hot springs. It can also be used to extract groundwater from deep wells. It can also be used in water lifting projects such as rivers, reservoirs and canals. It is mainly used for farmland irrigation and human and livestock water in alpine areas. It can also be used for central air conditioning cooling, heat pump unit, cold pump unit, city, factory, railway, mine and construction site drainage. The general flow can reach 5 ~ 650m3 / h and the lift can reach 10-550m. Submersible pumps often burn out motor windings due to lack of water in the pool. In view of this situation, we have sorted out several protection measures for submersible pump today: water shortage protection, motor water leakage protection, oil chamber water leakage protection, insulation resistance protection, winding overheating protection, bearing overheating protection, etc. 1. Abnormal power supply voltage is prohibited Because the low-voltage power supply line is relatively long, it is common that the terminal voltage of the line is too low. When the phase voltage is lower than 198 V and the line voltage is lower than 342 V, the speed of the submersible pump motor decreases. When it does not reach 70% of the rated speed, the starting centrifugal switch will be closed, causing the starting winding to be energized for a long time, heating and even burning the winding and capacitor. On the contrary, too high voltage causes the motor to overheat and burn out the winding. Therefore, during the operation of submersible pump, 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, stop the motor, find out the cause and eliminate the fault. 2. Confirm the correct rotation direction of the motor The rotation direction of the motor should be clarified. Now there are many types of high head submersible pumps that can discharge water during forward rotation and reverse rotation, but the water output is small and the current is large during reverse rotation. If the reverse time is long, the motor winding will be damaged. 3. Insulation resistance requirements for cable installation and submersible pump When installing the submersible pump, the cable should be overhead and the power line should not be too long. Do not force the cable when the submersible pump is launched or raised, so as to avoid breaking the power line. Do not sink into the mud when the submersible pump is working, otherwise it will cause poor heat dissipation of the motor and burn out the motor winding. During installation, the insulation resistance of the motor shall not be less than 0.5 megohm. 4. Avoid frequent switching Do not switch on and off the submersible pump frequently, because the backflow will occur when the electric pump stops running. If it is started immediately, the motor load will start, resulting in excessive starting current and burning out the winding. Due to the large current during startup, frequent startup will also burn out the motor winding of submersible pump.