Starting with load can cause damage to the motor; the actual use head is much lower than the pump nameplate head; the submersible pump works without water for too long.

The head of the centrifugal pump is used to overcome height and resistance. When the high-lift pump works at the high-lift point, its flow rate is the flow rate at the design point. If it works at a low head, it is equivalent to the pump outlet resistance is reduced. At this time, the flow rate of the centrifugal pump will increase, and the motor will be overloaded. If it exceeds a certain level, the motor will burn. For example, a water supply pump has a head of 50 meters and a flow rate of 50 cubic meters/hour. When it supplies water at a height of 50 meters, its flow rate is 50 cubic meters/hour. When it supplies water at a height of 40 meters, its height and resistance reduce its flow rate. It may reach 80-90 cubic meters/hour or more, and the motor will heat up or burn.

In addition, if it is a coil burning fault, it is mainly caused by overcurrent. Sometimes too high or too low voltage can also cause the coil to heat up and short-circuit, so first check whether the voltage during operation is too different from the rated voltage.

There may be several reasons for overcurrent short circuit:

1) The equipment is overloaded, causing the motor to run at rated current or over rated current for a long time. It should be noted that the starting current of the motor is 3-5 times the rated current, so it should be avoided to start the equipment with load or full load (mainly depending on the matching margin of the rated current of the motor and the normal operating current).

2) The motor works in a relatively humid working environment. Before starting the motor, the insulation to the ground and the phase insulation of the coil should be checked. The insulation requirements for different voltage levels are also different. You can refer to the relevant national standards for inspection. During the operation of the motor, attention should be paid to the waterproof and moisture-proof of the motor.

3) The mechanical failure of the pump causes the motor to be overloaded, and the current is too large to burn the coil.

4) There is a problem with the heat dissipation of the motor. Generally, the motor coil uses an air-cooled casing, and the submersible pump is a water-cooled casing. Large motors are mostly cooled by air-to-air heat exchangers and air-to-water heat exchangers. If the cooling water (air) is cut off, the coil cannot dissipate heat, which may burn the coil.