Normally, Steam Turbine speed is reduced to 1500 rpm to generate power by Alternator by using a Gear Box in between if the frequency is 50 Hz and 1800 rom if it is 60 Hz. For speed reduction purposes a gearbox system is followed by lubrication system which demands maintenance as well.
In case the power generation potential is up to or around 400 kW an Induction Generator instead of an Alternator can be used to generate power. For this the Turbines are designed to operate at 3025 or 3600 rpm based on the generation frequency required as 50 Hz or 60 Hz respectively. Such a Turbine is directly coupled to the Induction Generator without using the gearbox in between. This makes the system very simple in construction and operation as well.
An Induction Generator requires 2-3 times starting current for less than 3 seconds. Thus it is important to take this into consideration while deciding to use an Induction Generator.
Turtle Turbines has many successful installations in various industries with Induction Generator.