What are the reasons for a pump motor burning out?

Starting the motor under load can cause damage to it. First, it is necessary to determine whether the motor has burned out due to a problem with the bearings (a mechanical fault) or due to a problem with the coils (an electrical fault). If it is a fault with the coil, it is mainly caused by overcurrent; sometimes too high or too low voltage can also lead to the coil overheating and short-circuiting. Therefore, first check whether the voltage during operation differs significantly from the rated voltage. Overcurrent short circuits can be caused by the following reasons: 1. The equipment is operating under overload, causing the motor to run at its rated current or above for extended periods of time. It is particularly important to note that the starting current of a motor is 3-5 times its rated current; therefore, it should be avoided as much as possible to start the equipment under load or at full load (this depends mainly on the margin between the motor’s rated current and its normal operating current). 2. The motor operates in a relatively humid working environment. Before starting the motor, it is necessary to check the insulation of the coils with respect to ground as well as between phases. The insulation requirements vary depending on the voltage level at which the motor is used; relevant **standards can be referred to for such checks. During the operation of the motor, attention should be paid to its waterproofing and moisture resistance. 3. Mechanical failures of the pump cause the motor to be overloaded, resulting in excessive current that burns out the windings. 4. There is a problem with the motor’s heat dissipation. Ordinary motor coils use air-cooled housings, while submersible pumps use water-cooled housings. Large motors are often cooled using air-to-air heat exchangers or air-to-water heat exchangers. If the cooling water (air) is interrupted, preventing the coil from dissipating heat, it may burn out.

In whatever situation the motor burns out, it is always caused by overload – either because a weak motor is trying to drive a heavy load, or there is a problem with the pump, which needs to be checked one by one!

I’ll mention a few phenomena: 1. Whether it’s the motor or the pump, the bearings lack oil and the supports are damaged. 2 Excessive pressure builds up when only the inlet is open and the outlet is not, over a long period of time. 3 In cold weather, the viscosity of the fluid inside the pump is high, or when switching from a fluid with low viscosity to one with high viscosity, the high-viscosity fluid is not heated. 4 The pump impeller got stuck due to a hard object. A prolonged interruption in the cooling water supply to the pump caused the pump to operate at excessive temperatures. 6 After a power outage, power is restored suddenly, causing backflow of the medium; the outlet valve is not closed after power is restored, and the pump is started directly. 7. Starting the pump without rotating it first, or forcing the pump to start, etc., can all cause the motor to burn out.

Process technicians strictly adhere to operating procedures

Before starting the pump, turn it manually. If the oil lubrication is insufficient or if the shaft is stuck, starting the motor can easily lead to overload and motor damage. Improper operation of the valves, as well as high viscosity of the fluid – especially in winter – can also cause motor damage

The reasons why motors in various pumps burn out are different. Depending on the type of pump, it is essential to strictly follow its operating procedures; in addition, product quality is also a very important factor. Another point is whether there are any issues with the wiring of the motor protection device or its rated load capacity. For example, if the thermal relay does not activate after overload, or if the motor is selected with an oversized capacity, it can be damaged. If many pumps are having problems, it’s necessary to thoroughly check whether there are any issues with the selection or wiring of the thermal relays in the MCC station when the opportunity arises.

There are two possible main reasons: 1. The motor has been overloaded for a long time； 2. Moisture entering the motor reduces its insulation, leading to a short circuit and burnout during startup.

Our company has experienced cases where motors were damaged due to issues with the wiring of thermal relays. The MCC room purchased a large number of thermal relay junction boxes, but it turned out that the wiring for 2 of these devices was incorrect from the time of manufacture. One of the thermal relays caused a 120KW motor to burn out, while another thermal relay led to the destruction of two 30KW motors. It was only then that it became clear that the problem was due to the thermal relays in the MCC room; apparently, a claim was made against the thermal relay manufacturer! ! !

The pump is running idle, in reverse, or has an excessively high power setting

Motor burnout during startup: 1. No rotation of the pump before startup. 2. The medium inside the pump has high viscosity at the time of startup. 3. The motor has not been maintained for a long time. 4. The medium inside the pump freezes, increasing the load on the motor during startup. 5. Incorrect wiring of the motor. 6. The outlet valve of the pump is open, causing the pump to start under load. Motor burnout during normal operation: 1. Heavy oil is suddenly introduced during normal operation. 2. The pump operates under overload conditions for an extended period. 3. Cold weather causes the heating system in the medium pipelines to stop working, resulting in increased viscosity of the medium. 4. Pump failures increase the load on the motor. 5. Motor bearing failures lead to motor burnout. 6. The cooling water supply to the motor is interrupted for a long time, causing overheating. 7. Power is restored suddenly after a power outage, causing the pump to start under load. 8. Hard objects get trapped inside the pump’s impeller, causing the motor to operate under overload

Could it be that there are mistakes in the selection and use of the pumps? The manuals for pumps usually include their performance curves, and it is essential to choose an outlet pressure that falls within the appropriate range when using them. If the outlet pressure is too low, the flow rate will be too high, which leads to increased energy consumption and a higher risk of damaging the pump.