Ques. What special provision is made for cooling the bearings?
Ans. They are in some cases water cooled.
Turbine Driven Alternators.—Although the principle of operation of the steam turbine and that of the reciprocating engine are decidedly unlike, the principle of operation of the high speed turbine driven alternator does not differ from that of generators designed for being driven by other types of engine or by water wheels. There are, therefore, with the turbine driven alternator no new ideas for the operator who is familiar with the older forms to acquire.
It must be obvious that the proportions of such extra high speed machines must be very different from those permissible in generators of much slower speeds.
Ques. How does a turbine rotor differ from the ordinary construction?
Ans. It is made very small in diameter and unusually long.
Ques. Why?
Ans. To reduce vibration and centrifugal stresses.
Ques. What are the two classes of turbine driven alternators?
Ans. They are classed as vertical or horizontal.