Generator of a power station can be classified into different fields depending upon the mechanical arrangement.(bearing arrangement)
1. Umbrella Type
Due to low speed (80 – 200 rpm), it does not require a top guide bearing, and combines bottom thrust and guide bearing.
2. Semi-Umbrella Type: It is applicable to medium speed (130- 250rmp) with the combination of bottom thrust, guide bearing and top guide bearing, where the latter one is supported by a light bracket. Cost wise more expensive than umbrella type.
3. Standard Type: This is the most expensive generator design for high speed applications (170 - 1000rmp) with small rotor diameter. Here Top mounted thrust & guide bearing supported on a heavy bracket