Why electric generator is attached to LP turbine and not on HP Turbine side ?

Question

Why electric generator is attached to LP turbine and not on HP Turbine side ?

Answer 1

Not sure I understand your question completely but I will try and explain.  One turbine in a power plant contains different stages,typically 1 high pressure turbine stage followed by 3 or 4 low pressure turbine stages.  All these stages are on the same turbine shaft and make up the whole "turbine".  The high pressure turbine stage is the first stage because the steam is the hottest and at the highest presssure and the low pressure turbines follow, therefore you could not attach the generator directly to the HP turbine but it doesnt really matter because all stages share a common shaft so the generator is receiving power from all the stages of the turbine combined.

Answer 2

because the generator will be on the cooler side and typically, the govenor for the steam turbine has to be on the HP side so it reside there.

Answer 3

If you're referring to a Combustion Gas Turbine, which I believe you are...then...

The Air compressor feeding the Combustion Chamber needs a driver. It is directly connected to the HP (or Air Compressor) Turbine) by a shaft.

After doing this work, the HP turbine exhaust containing huge amounts of residual energy, is fed through Variable Angle Nozzles on to the Load (LP) Turbine rotor(s). This turbine takes the load of the Generator (or a High Power Gas compressor ..etc).

In this way, changes in load are easier to compensate for by the Speed Control Systems. Load changes tend to affect the Load Turbine speed. The Governor system will vary the angle of the Variable Nozzles thus increasing or decreasing LP turbine power ouput by maintaining the required speed. As this takes place, the HP Turbine speed will tend to increase or decrease due to the varying back pressure on the HP turbine exhaust gases feeding the nozzles.

The Dual Governor system will adjust the Fuel supply to the Combustion Chamber(s) in order to maintain HP Turbine Speed.

(There's a fair bit more to it than that but, too much for this entry)..

Answer 4

All of the turbine speed governor and steam throttling devices, safety trip detectors and valves and high pressure seals are on the high pressure end of the shaft plus the lubrication system, while only the low end shaft bearing is on the other end. The low end shaft seal is much simpler. So that is why the driven generator, compressor or pump are coupled to the low pressure end of the steam turbine shaft.

Answer 5

On a common shaft the high temperatures are on the high pressure side.

Since generators have to be cooled, it makes sense to keep them

at a distance from the worst outside heat,