For large alternators hydrogen is used instead of air because of following reasons. Given below are few reasons for this practice:
- Low Windage Losses: Hydrogen has lower viscosity than air, resulting in lower windage losses. Windage losses occur due to the friction between the rotating components and the surrounding medium (air or hydrogen). The lower viscosity of hydrogen reduces these losses, contributing to higher efficiency in large generators.
- High Thermal Conductivity: Hydrogen has a significantly higher thermal conductivity compared to air. This means it can efficiently carry away heat from the generator windings and other critical components. High thermal conductivity allows for better heat transfer and helps in keeping the alternator operating at lower temperatures.
- Reduced Hot Spot Formation: The high thermal conductivity of hydrogen ensures more uniform cooling across the generator winding. This reduces the likelihood of hot spots, localized areas where temperature can become excessively high and potentially lead to insulation degradation or failure.
- Lower Windage Noise: The lower viscosity of hydrogen not only reduces windage losses but also results in lower windage noise. This is especially important in applications where noise reduction is a consideration, such as in power plants located in residential areas.
- Less oxidation: It produces less oxidation of windings