Why turbo alternators are provided with hydrogen cooling?
Hydrogen-cooled turbo generators are designed to provide a low-drag atmosphere and cooling for single-shaft and combined-cycle applications in combination with steam turbines. Because of the high thermal conductivity and other favorable properties of hydrogen gas, this is the most common type in its field today.
Why hydrogen is used in alternator?
The solution to this is to use hydrogen as the coolant gas. Hydrogen offers a number of beneficial characteristics as a coolant gas to bathe the alternator windings and removing the generated heat. These include: Hydrogen has the highest thermal conductivity properties of any gas.
What are the two types of turbo alternators?
On account of the high rotating speeds, two types of turbo- alternator rotor designs, radial-slot type and parallel-slot type are used.
How does hydrogen cool a generator?
So why use hydrogen to cool a generator? Despite its reputation, hydrogen gas has qualities that make it a superior heat transfer media and internal atmosphere for a generator. Hydrogen is much less dense that air. Combine this with the fact that hydrogen conducts seven (7) times more heat than air.
At what percent is hydrogen maintained in a hydrogen-cooled generator?
Hydrogen purity must be maintained above the UFL (upper flammability limit) of 75%. Most generators have alarms set at levels greater than 90% with an automatic trip and purge if purity falls below 88%. Additionally, hydrogen purity effects efficiency.
Can hydrogen be used as coolant?
Hydrogen is used as a high-performance gaseous coolant. Its thermal conductivity is higher than all other gases, it has high specific heat capacity, low density and therefore low viscosity, which is an advantage for rotary machines susceptible to windage losses.
What are the advantages of hydrogen cooling?
Hydrogen cooled power generators are more efficient and have less mass of materials of construction than their air-cooled cousins. Hydrogen gas is 7 times more effective as a heat transfer medium than air and 1/14th the density, resulting in less friction losses and more fuel converted to electricity.
Can hydrogen be used for cooling?
Air, water and oil have all been used for cooling. But hydrogen’s low density, high specific heat and thermal conductivity make it a superior coolant for this application. But hydrogen is an effective way to cool the generator and allows power plant operators to get a lot more megawatts out of a smaller generator.
What is the highest possible speed of turbo alternator?
3000 rpm
What is the highest possible speed of turbo alternators? Steam turbines have good efficiency at higher speeds only. Therefore maximum speed of turbo alternators used in those power plants are 3000 rpm with two poles and next possible speed is 1500 rpm with 4 poles.
Which type of rotor is best for turbo alternator?
Smooth cylindrical type rotor is generally used for high speed alternators or turbo alternators.
At what percent is hydrogen maintained in a hydrogen cooled generator?
Is hydrogen a good coolant?
What type of cooling is used in turbo alternator?
Small turbo-alternators may be air cooled, but for large size units hydrogen cooling is used. The turbo alternators have horizontal configuration. The rotor of turbo-alternators are of small diameter as compared to its length.
Which type of alternator is used for 500MW generating set?
Hydrogen cooling can be used for 500MW generating sets. The turbo alternator have high rated speed. The capacity of turbo alternators is upto 500MW. Small turbo-alternators may be air cooled, but for large size units hydrogen cooling is used. The turbo alternators have horizontal configuration.
Which type of alternator is used in thermal power station?
Hydrogen cooling can be used for 500MW generating sets. Following are the special features of a turbo alternators used in thermal power station: The turbo alternator have high rated speed. The capacity of turbo alternators is upto 500MW. Small turbo-alternators may be air cooled, but for large size units hydrogen cooling is used.
Can hydrogen be used as a coolant in a generator?
A hydrogen-cooled generator can be significantly smaller, and therefore less expensive, than an air-cooled one. For stator cooling, water can be used. Helium with a thermal-conductivity of 0.142 W/(m·K) was considered as coolant as well, however its high cost hinders its adoption despite its non-flammability.
