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Hydrogen is used in alternator for
Reduce distortion
Cooling
Increase power factor
Reduce losses
Cooling
Hydrogen is used in large alternators primarily as a cooling medium due to its high thermal conductivity and low density. Its superior heat transfer capabilities allow for higher current densities in the stator and rotor windings, resulting in a more compact and efficient machine design.
Hydrogen is used in large alternators primarily as a cooling medium due to its high thermal conductivity and low density. Its superior heat transfer capabilities allow for higher current densities in the stator and rotor windings, resulting in a more compact and efficient machine design.
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Hydrogen has a thermal conductivity approximately 7 times that of air, which allows it to carry heat away from the windings and core much more effectively. Furthermore, because its density is about 1/14th that of air, the windage losses (friction losses due to rotation) are significantly lower. Operating at pressures above atmospheric levels further enhances the cooling capacity without increasing mechanical drag.
Hydrogen cooling is essential for turbo-alternators exceeding 50-100 MW.
The hydrogen system must be kept in a gas-tight casing to prevent leakage and avoid explosive mixtures with oxygen.
Oil-sealed bearings are used to prevent hydrogen leakage along the shaft.
Higher pressure hydrogen (e.g., 3-4 kg/cm┬▓) allows for greater cooling capacity.
Significant reduction in windage losses compared to air cooling.
Higher thermal conductivity allows for increased power ratings for the same physical size.
Absence of oxygen prevents internal oxidation and corona damage to insulation.
Hydrogen forms an explosive mixture with air, necessitating complex sealing and purging systems.
Higher initial capital cost due to the requirement for a sealed casing and gas handling plant.
Large utility-scale thermal power plant turbo-alternators.
High-speed rotating electrical machines where windage losses are dominant.
The purity of hydrogen must be maintained above 95% to ensure safety against explosion.
Option A is incorrect as distortion is controlled by winding design and pole shaping, not the coolant.
Option C is incorrect as the power factor depends on the load characteristics (capacitive/inductive), not the coolant.
Option D is partially true as windage losses are reduced, but 'Cooling' is the primary functional intent of the coolant.
B is correct тАФ Hydrogen is used in alternators primarily as an efficient cooling medium due to its high thermal conductivity and low density, which minimizes windage losses.
Always remember that in large alternators, the 'coolant' selection is driven by thermal management; for smaller machines, forced air is usually sufficient.