Cable heating and pressure drop are two factors of power line specification. Control the constant current density to limit the temperature rise of the cable, in addition, the longer the length of the cable used for submersible water pump, the greater the voltage drop, the use of the cable, the start of the motor, operating performance and higher reliability. Cable heating and pressure drop for submersible water pump are two factors for power line specification. Control the constant current density to limit the temperature rise of the cable, in addition, the longer the cable length, the greater the voltage drop, the use of the cable, the start of the motor, operating performance and higher reliability. Therefore, the same good submersible motor, when equipped with submersible pump head, different cable length is not the same, the requirements are different cable cross section. According to GB/T2816 "deep well submersible pump" standard, water temperature is 25 ℃, rated current, cable voltage drop should not exceed 5% of rated voltage. Therefore, the available power supply voltage is 380V, the submersible motor of different power has certain specifications, and the maximum length of cable for submersible pump is different. When the power voltage is higher, the power transformer is more stable or relatively large, the voltage is higher and more stable, the underground submersible motor is equipped with the same specification of cable running length (or equipped with cable) according to the specific situation to reduce the cross section appropriately to reduce the cable configuration cost). When the deep well submersible pump has high lift and the motor is deeper, the cable length is longer, but it is a poor quality power transformer. Motor starter is very difficult: starting current is very large, submersible water pump cable voltage drop is very large. Therefore, the motor terminal voltage is low. In addition, the starting current will be further increased, and the starting torque of the cable voltage drop will be reduced, forming a vicious circle, which is not only difficult to start the motor, forced start, and may damage the motor winding. It is better to increase the supply voltage of the transformer.