Why LM6000 PC using two shafts?

The compression ratio for LM6000 PC is quite high (30:1 usually) compared to a conventional Gas turbine, for achieving this high ratio the compressor design with two shafts is more efficient than a single shaft. So basically the efficiency of compression increases if you increase the no.of shafts, ie 3 shaft will be more efficient than 2 shafts. But the cost also increases with the no.of shafts involved. So finally if you see the trade off 2 shaft model works out to be the best.

Ralini Pradeep Adatrao