Hydrogen is used in large alternators mainly to cool the machine.

Introduction:
Large alternators are used in power plants, industries, and other applications where high electrical power is required. These alternators generate a significant amount of heat during operation due to the flow of electrical current through the windings. Cooling is necessary to maintain the temperature within safe limits and prevent damage to the machine.

How is Hydrogen used for cooling?
Hydrogen gas is commonly used as a cooling medium in large alternators. It offers several advantages over other cooling methods such as air or water.

1. High thermal conductivity:
Hydrogen has a high thermal conductivity compared to air or water. This means it can absorb and transfer heat more efficiently, thereby enhancing the cooling process. The high thermal conductivity of hydrogen allows for better heat dissipation from the alternator windings.

2. Low density:
Hydrogen has a low density, which means it has less mass per unit volume. This property enables the gas to flow more easily through the cooling channels and around the windings, providing better cooling coverage. The low density of hydrogen also reduces the pressure drop across the cooling system, resulting in reduced energy consumption.

3. Chemical stability:
Hydrogen is chemically stable, which means it does not react with the materials used in the alternator construction. This stability ensures that the cooling system remains free from corrosion or degradation, leading to a longer lifespan of the machine.

4. Non-conductive:
Hydrogen is a non-conductive gas, meaning it does not conduct electricity. This property is crucial in electrical machines like alternators, as it prevents the occurrence of electrical faults or short circuits caused by the cooling medium.

Conclusion:
In summary, hydrogen is used in large alternators mainly for cooling purposes. Its high thermal conductivity, low density, chemical stability, and non-conductive nature make it an ideal choice for efficiently dissipating heat from the windings. By using hydrogen as a cooling medium, the alternator can operate at safe temperatures, ensuring optimal performance and longevity of the machine.