It is undeniable that an electric generator is required to have an excellent cooling system to remove heat created therein. If the heat in the generator is not immediately removed, he will directly damage the generator itself. Excessive heat can damage the coils in the extreme rotor, stator, it will even burn components of the generator.
Hydrogen gas is the best choice to replace the air as the cooling medium generator primarily on large-sized generators. Hydrogen chosen because its characteristics were excellent when used as a coolant, call it a high thermal conductivity (0.168 W / m · K), its density is very light, and also a high specific heat. With these characteristics, making hydrogen 7-10 times better than air conditioning if used. This can be likened to generate the same electrical power, air-cooled generator will be sized 7-10 times greater than the hydrogen-cooled generator. Therefore, for large-sized generators, hydrogen cooling systems will become more economical than using the air conditioning. Actually, helium gas has good thermal conductivity as well (0.142 W / m · K), but because the price is much more expensive than hydrogen, then it is not used.
Generators are formed from millions of winding wire arranged in a coil on the two sides of the different sectors the rotor and stator. The coils will generate very high heat during generator operation. Hydrogen as a coolant to flow generator will envelop these coils, absorbing heat, and throw it in the cooling heat exchanger. There are two types of hydrogen in the generator cooling system commonly used is hydrogen cools the generator rotor stator at the same time, and generator with hydrogen cooling for the water on the rotor and stator side. Generators that use hydrogen coolant in the water on the rotor and stator usually large and Megawatt electricity generating over 500 MW.
Hydrogen-cooled generator only circulate hydrogen to all sides of the generator coil both rotor and stator. An axial fan mounted a generator shaft to circulate hydrogen duty to continue rotating the reach all sides of the generator. However, the flow of hydrogen does not reach the inside of the rotor coil, it only cools the outer side only so that it can be said stator coil is cooled only indirectly (indirect cooler). At some point in accordance with the above picture are the cooling heat exchanger which serves to cool the hydrogen that has been absorbing heat generator components. The hydrogen cooling medium is water continues to circulate and dissipate heat out of a system.
For hydrogen-cooled generators and water, they share the task so that the hydrogen into water while the rotor cooling media served to cool the stator coil. Should the previous system, with assistance from the hydrogen circulating fan that rotates the rotor so that it can reach all parts of the rotor. At the end of the circulatory system, the hydrogen goes into the cooling heat exchanger to expel heat to medium water. While on the stator, the water becomes cooler capable of reaching all parts of the coils are not getting the previous system. With such a cooling system, recorded the largest generator design which is capable of producing 858 megawatts of electricity.