How to deal with the dampness of Mining Electric Motor?

1. External drying treatment
1. Hot air dryer method
Operation steps
Select a hot air blower with appropriate power, which is generally determined according to the size and degree of dampness of the motor. Aim the hot air blower outlet at the motor and keep an appropriate distance (usually 20-30 cm) to avoid local overheating.
Turn on the hot air blower so that the hot air blows evenly to the motor housing, end cover, terminal box and other parts. During the blowing process, keep moving the hot air blower to ensure that all parts can be fully dried. For example, you can start from one side of the motor, gradually move to the other side, and then blow dry from top to bottom.
Continue blowing for a period of time. Generally, small motors may take 2-3 hours, medium-sized motors 3-5 hours, and large motors may take 5-8 hours or even longer. The specific time depends on the actual dampness.
Precautions
The temperature of the hot air blower should not be too high, generally controlled at around 80-100°C, so as not to damage the insulation material or other components of the motor. During the drying process, the surface temperature of the motor should be closely observed. An infrared thermometer can be used to measure it to prevent local temperature from being too high.
At the same time, pay attention to the environment around the motor and avoid using a hot air blower in an environment with flammable and explosive gases or dust to prevent safety accidents.
2. Infrared bulb drying method
Operation steps
Install infrared bulbs at appropriate locations around the motor. The number and power of the bulbs are selected according to the specifications and moisture level of the motor. Generally speaking, for small motors, 2-3 250-500 watt infrared bulbs may be sufficient; for large motors, more and higher-power bulbs may be required.
Turn on the infrared bulb so that the infrared light emitted by the bulb is irradiated onto the motor. Because infrared light has a thermal effect, it can evaporate the moisture in the motor. During the irradiation process, adjust the distance between the bulb and the motor so that the surface of the motor is heated evenly. Usually, the distance is controlled at 30-50 cm.
The continuous irradiation time is similar to the hot air blower drying method. It is determined according to the size and moisture level of the motor. During the drying process, check the dryness of the motor regularly.
Precautions
Prevent the infrared bulb from direct contact with the motor housing to avoid scalding the motor housing or causing a fire. At the same time, pay attention to the heat dissipation of the bulb to avoid overheating and damage to the bulb due to long-term use.
As with the hot air blower drying method, the operation should be carried out in a safe environment and away from flammable and explosive substances.
2. Internal drying treatment
1. Current drying method
Operation steps
First, connect the three-phase windings of the motor in series or in parallel (determine the connection method according to the power supply voltage and the rated voltage of the winding), and then connect to a low-voltage AC power supply. The power supply voltage is generally 3% - 10% of the rated voltage of the motor. For example, for a motor with a rated voltage of 380V, an AC power supply of 12 - 38V can be connected.
By adjusting the output current of the power supply, the current in the motor winding is about 50% - 70% of the rated current. This current will cause the winding to heat up, thereby evaporating the internal moisture. During the drying process, the current should be closely monitored to prevent excessive current from causing overheating and damage to the winding.
The drying time is long and may take from several hours to dozens of hours, depending on the degree of moisture in the motor. The degree of drying can be judged by measuring the insulation resistance of the winding. When the insulation resistance reaches the specified value (such as the insulation resistance between phases and the insulation resistance to ground are both greater than 0.5 megohms) and is stable, the drying can be considered complete.
Precautions
Before the current drying method is used, it must be ensured that the insulation of the motor is not completely damaged, otherwise it may cause more serious faults such as short circuits.
During the drying process, safety precautions should be taken, such as setting up warning signs to prevent people from accidentally touching the live parts. At the same time, the temperature of the motor should be checked regularly. Generally, the temperature of the motor winding should not exceed 70-80°C.
2. Desiccant drying method (suitable for mild moisture)
Operation steps
Open the end cover of the motor (while ensuring safety) and place a desiccant inside the motor. Commonly used desiccants include silica gel, calcium chloride, etc. Silica gel has good moisture absorption performance, and its color will change after moisture absorption (such as from blue to pink), which is convenient for judging the degree of moisture absorption.
Place the desiccant evenly in the free space inside the motor, then seal the motor end cover to allow the desiccant to absorb moisture inside the motor. Depending on the degree of moisture in the motor, the time to place the desiccant may vary from 1 to 3 days.
Notes
When placing the desiccant, avoid direct contact between the desiccant and the windings and other parts of the motor to prevent corrosion or other damage to them.
When the desiccant reaches saturation (such as the color of the silica gel completely changes), the desiccant needs to be replaced in time to ensure the drying effect.
III. Inspection and maintenance after overall treatment
1. Insulation resistance detection
After the drying treatment is completed, use an insulation resistance meter (megohmmeter) to detect the insulation resistance of the motor. Measure the phase-to-phase insulation resistance and the insulation resistance to ground of the motor respectively. When measuring, operate according to the use specifications of the megohmmeter, such as correctly connecting the terminal of the megohmmeter to the corresponding part of the motor, shaking the handle to make the megohmmeter reach the specified speed (generally 120 rpm), and read the insulation resistance value.
If the insulation resistance value reaches the specified standard (such as the phase-to-phase insulation resistance and the insulation resistance to ground are both greater than 0.5 megohms), it means that the insulation performance of the motor has basically recovered; if the insulation resistance value is still low, it may be necessary to further dry or check whether the motor has other faults.
2. Maintenance measures
Inspect and maintain the bearings of the motor. If the bearings are affected during the moisture process, such as the grease deterioration, clean the bearings and add an appropriate amount of grease again. At the same time, check the wear of the bearings. If there are parts with severe wear, replace the bearings in time.
Check the terminal box of the motor to ensure that the terminal is firmly connected, and treat it with moisture-proof treatment, such as applying moisture-proof sealant. Clean the vents of the motor to ensure good ventilation, and install or replace dust filters to prevent dust from entering the motor.