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Gas Turbine with Induction Generator
Could a gas turbine such RB211 GT30 or RB211 GT62 run a induction generator?
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Hello all:

I'm involved in a project for an isolated system that consist of three gas turbo generators (30MW) each. The load to feed is about 60MW.

The idea is to replace one of these three synchronous generators by an induction generator. The synchronous generator have a small range of rpm to go from zero load to full load, that is, 3595 rpm working as motor, 3600 zero load and 3607 rpm, full load.

My question is: the gas turbine have this thin range of control to warranty the operation? What's the minimum variation in rpm that gas turbine FSR control can deliver?

thanks and regards

1 out of 2 members thought this post was helpful...

vladimir,

Why do you think it's necessary to allow a generator to operate at a wide range of speed in order to produce electrical power? What is it about this system you're working on that makes you think one (or more) generators need to be capable of operating at various speeds in order to produce electrical power?

The design of the axial compressors of most gas turbines determines the allowable speed range for the unit. Axial compressors are pretty unique machines, and most are designed to operate in a fairly narrow range (especially heavy duty gas turbines).

But, I'm still curious why you or someone thinks it would be advantageous to have a single induction (asynchronous) generator operating on a grid? What does speed have to do with electrical power?

0 out of 1 members thought this post was helpful...

Hello CSA, thanks for your answer,
See my answers in each question.

Why do you think it's necessary to allow a generator to operate at a wide range of speed in order to produce electrical power?

I know the generator operate in a narrow range of speed between 100 to about 105% of it, using synchronous generators in droop mode. Actually the speed doesn't change just the reference speed. With an asynchronous generator the power variation between 0 to 100 represent a smaller, but real, variation of speed. for two pole generator the speed goes from 3600, zero load to 3607, full load.

My question is: can the gas turbine sustain this narrow range of speed? It's about 4MW per rpm!

What is it about this system you're working on that makes you think one (or more) generators need to be capable of operating at various speeds in order to produce electrical power?

The system actual have three synchronous generators, 30MW each. And other one similar in stand by. We want to replace one of this generators by an asynchronous.

The design of the axial compressors of most gas turbines determines the allowable speed range for the unit. Axial compressors are pretty unique machines, and most are designed to operate in a fairly narrow range (especially heavy duty gas turbines).

Could you tell me whats the fairly narrow range for the compressor operation for the aeroderivative turbine RB211 rolls roice or STG-A35 Siemens?

But, I'm still curious why you or someone thinks it would be advantageous to have a single induction generator operating on a grid?

because of, in this case, the small grid is on a oil platform, and we need to reduce weight.

What does speed have to do with electrical power?

The speed control is the power generate from the turbine. the people involve on the project are concerning about what is the minimum speed variation that the turbine valves can support.