Comparison of Generator with Same Insulation Class & Different Class Temp. Rise

You have asked this before as a guest? Despite 30 views, no answers. Maybe i should not be giving my views here since i am no expert in generators, but....

... if you are using Class F insulation, why would you restrict yourself to Class B temperature rise? Overkill isn't it? 50°C is the margin. Why so much overdesign?

i can understand this if this was a fire-pump or something similar, where the risk of loss of life is there...not in a generator.

As generator is important piece of equipment, so selecting Insulation class F and temp rise limited to class B shall result in extending service life of generator.

As there is thumb rule any increse/fall of 10 dig operating temperature half/double the useful life of insulation of 20,000 hrs.

Any further readings on subject, pl suggest.

You have posted the question in last 3-4 days and I had posted my reply today. please see the same

Dear PCCHATUR,

Thanks for reply.

Will you pl. suggest values of flux density (or corel loss in Watts/KG of iron core) for two machines of 25 MW with Insulation class F and different temp class rise.

I hope you to have answer...

Generators are not designs are not changed for such features (Class F temperature rise and class B temperature rise). Each generator is designed for a particular MVA rating using class insulation with class B temperature rise. If you ask for generator with class F rise, you will be offered a smaller MVA generator to be operated at your asked rating which will have class rise at this rating.

As far flux density or watts/Kg for two generators, steel grade is not changed for such changes. Generally 1.5W/Kg grade of steel is used for Turbo Generator core design.

I assume the figure loss in iron 1.5W/Kg is for Machine with insulation class F and temp rise class B.

What would be figure of iron loss for Machine with insulation class F and temp rise class F. I mean iron loss value at operating point.

Again I hope you have answer.

Thanks in advance for your answer.