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How to deal with the dampness of diesel generator sets after the spring rainy season?
June 22, 2022
The spring in the south, rainy, not rainy, when it meets back to the south, even the air is humid, making the chances of diesel generator sets damp greatly increased, especially outdoor use of diesel generator sets face more serious unit moisture problems, in the case of damp start diesel generator sets will have unexpected trouble. Users can use a 500-volt megohm meter to test the insulation resistance of the generator set when checking whether the generator set is wet. If the resistance value is less than 1 megohm, it indicates that the generator set has been wet. At this time, measures must be taken to dry the unit in time to avoid the failure of the unit. Drying unit can refer to the following methods.
I. Load drying method
First of all, check the appearance of the unit, if only the surface is wet, you can use the load drying method to dry. After drying, the generator set can be operated at 50% of the rated current load. Then increase the value to 65%, 85% and 100% of the rated current respectively. Each stage of the load is run for 4 to 5 hours. During the drying process, the insulation resistance of each winding should be tested periodically. After the insulation resistance value reaches the requirement, the drying can be stopped and the generator set is operated normally.
Second, the cold work method
With the AVR power cord disconnected, generator sets left in dusty and humid environments for long periods of time can be idled for about 10 minutes. This may be sufficient to dry the winding surface and increase the insulation resistance value to greater than 1 megohm to generate current. The machine can resume normal operation.
Third, the short-circuit current drying method
The first step is to ensure the safety of the mechanical and electrical operation of the unit on the generator set. The output terminals of the generator set are short-circuited by means of a short-circuit rod. The shorting rod used should be able to withstand the rated current of the generator set. Disconnect the AVR and use an external 0 to 24 VDC power supply. Adjust the DC supply voltage so that the stator current per phase is 50-70% of the rated current. Stop the machine every 30 minutes. Disconnect the external excitation power supply and test and record the insulation resistance value. If the insulation resistance value is greater than the specified value, you can remove the external DC power supply, reconnect the AVR, and retry the operation. The generator set cannot be operated at the rated speed, but a constant speed should be maintained to avoid temperature instability.
Fourth, the hot air method
Remove all the covers of the generator set, so that the practice is conducive to the discharge of moist air. Use a hair dryer to blow in through the air inlet of the generator set. Please note that the heat source and the winding should be kept at least 00mm to avoid overheating and causing insulation damage. Control the surface temperature of the windings. The surface of the winding measured with a thermometer should not exceed 85°C and the air inlet should not exceed 90°C. Continue to blow and record the insulation resistance value every half hour. When the value is greater than the specified value, the drying process is complete. Remove the blower, close all the protective cover, and then retry.
V. Oven (furnace) baking method
In places where there are conditions, the motor as a whole (preferably the stator and rotor disassembled) into the oven (furnace) in a gradually rising temperature baking. The oven (furnace) should be able to ventilate in order to take away the moisture in the motor, and preferably laminated, the inner layer of the motor, in the outer layer of heating, the temperature of the inner layer to maintain at 90-100 ° C, and can not have open fire, soot and other combustible and corrosive gases exist. Generally require continuous baking 8 ~ 18h, in the middle can measure the insulation resistance of the motor several times, until it reaches the specified value and stable.
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