As an emergency power source, diesel generator sets need to work continuously for a long time during use. With such a large load, the temperature of the generator set has become a problem. To maintain good uninterrupted operation, it is necessary to keep the temperature of the generator set within an acceptable range. This requires everyone to understand the temperature rise requirements and cooling methods.
1： Heating requirements
According to the different insulation levels of diesel generators, their temperature rise requirements vary. Generally, when the generator is in operation, the temperature of its stator winding, excitation winding, iron core, collector ring, etc. is about 80 degrees Celsius. If it exceeds 80 degrees Celsius, it is considered that the temperature rise is too high.
2： Cooling method
Different types and capacities of generators have different cooling forms. But the cooling medium used is generally air, hydrogen, and water. Taking the turbo synchronous generator as an example, its cooling system is closed and the cooling medium is recycled.
(1) Air cooling
Air cooling is achieved by using a fan to supply air. Cold air is used to blow and dissipate heat at the end of the generator set winding, stator, and rotor. The cold air absorbs heat and becomes hot air. After the initial convergence of the air between the stator and rotor, it is discharged through the air duct of the iron core and cooled through a cooler. The cooled air is then fed into the generator by a fan for internal circulation to achieve heat dissipation. Medium and small synchronous generators generally use air cooling.
(2) Hydrogen cooling
Hydrogen cooling uses hydrogen as the cooling medium, and its heat dissipation performance is better than that of air. For example, most steam turbine generators use hydrogen cooling.
(3) Water cooling
Water cooling is achieved by using a dual water internal cooling method of the stator and rotor. The cold water of the stator water system flows through a water pipe to the inlet ring installed on several stator seats, and then flows through an insulated pipe to each coil. After absorbing heat, it is collected through an insulated water pipe to the outlet ring installed on the base, and then discharged into the external water system of the generator for cooling. The cooling of the rotor water system is first fed into the inlet support installed at the shaft end of the exciter, and then flows into the center hole of the shaft. It flows along several meridional holes to the water collection tank, and then flows through the insulation pipe to each coil. After the cold water absorbs heat, it flows into the outlet water tank through an insulated pipe, and then flows to the outlet support through the drainage hole on the outer edge of the outlet water tank, which is led out by the outlet main pipe. Due to the significantly higher heat dissipation performance of water compared to air and hydrogen, newly built large power generation units generally use water cooling.