Diesel generator sets used outdoors are often exposed to harsh weather conditions. Improper handling can lead to moisture problems, especially when the generator motor becomes damp. Moisture significantly affects the performance, insulation, and lifespan of the generator. Therefore, timely and proper drying methods are essential to restore normal operation.
Once a generator motor becomes damp, it must be dried immediately. The drying method should be selected based on the motor capacity and the degree of moisture exposure. Two commonly used drying methods are described below.
When conditions allow, the motor should be placed entirely into an oven or furnace. For better results, the stator and rotor can be disassembled before drying.
The temperature should be increased gradually, and proper ventilation must be ensured to remove moisture effectively. A double-layer (sandwich) heating structure is recommended, where the inner layer holds the motor and the outer layer provides heat.
The inner temperature should be maintained between 90°C and 100°C. Open flames, smoke, or corrosive gases must be strictly avoided. The drying process typically lasts 8 to 18 hours. During this period, insulation resistance should be measured multiple times until it reaches the specified stable value.
For AC generators, another effective method is the steady-state short-circuit current drying technique.
First, short-circuit the three phases at the generator outlet. Then, increase the generator speed to a temporary level and maintain it. Adjust the excitation current so that the stator short-circuit current reaches 50%–70% of the rated value and maintain this for 4–5 hours.
Next, increase the excitation current further until the short-circuit current reaches 80%–100% of the rated value. During this process, ensure the coil temperature remains below 85°C. Measure insulation resistance and coil temperature every 30 minutes until the insulation resistance stabilizes at the required level.
During operation, the cooling water temperature should be maintained between 75°C and 90°C. This range ensures maximum engine power output, optimal fuel efficiency, and minimal component wear.
If the temperature is too high or too low, or if the thermostat is removed improperly, the cooling system performance will be reduced or may fail completely.
Diesel engine combustion generates extremely high temperatures, with cylinder gas temperatures reaching 1800°C to 2000°C. Only about 30%–40% of this energy is converted into mechanical power, while 20%–25% must be removed by the cooling system.
If the cooling system fails or operates abnormally, it can lead to overheating, reduced efficiency, or serious engine damage.
The cooling water should be clean, soft, and slightly alkaline. It must not contain corrosive substances. The recommended pH value is between 8 and 11 to reduce scaling and blockage within the cooling system.
Using proper coolant instead of plain water is recommended for better protection against corrosion and deposits. Regular cleaning with chemical agents is also necessary to maintain efficient heat transfer and circulation.
In regions or seasons where the ambient temperature is above 5°C, anti-rust additives should be mixed with the cooling water. This helps reduce corrosion and scale buildup inside the cooling system.
In colder conditions, antifreeze should be used in closed-loop cooling systems to prevent freezing and damage.
To facilitate engine startup in cold weather, hot water (around 80°C) can be added to the cooling system, or the lubricating oil can be preheated before starting.
After shutdown, when the engine temperature drops to 50°C–60°C, the drain valves of the radiator and cylinder block should be opened to remove water from the cooling system. This helps prevent freezing and corrosion during idle periods.
Proper handling of moisture and correct cooling system management are essential for the safe and efficient operation of diesel generator sets. By applying appropriate drying methods and maintaining optimal cooling conditions, operators can significantly extend equipment lifespan and ensure reliable performance in all environments.
