he head of operating.

[Illustration: FIG. 33]

Generator

The turbo-generator, which constitutes the electrical end of this unit,
is totally enclosed to provide for noiseless operation, and forced
ventilation is secured by means of a small fan carried by the shaft on
each end of the rotor. The air is taken in at the ends of the generator,
passes through the fans and is discharged over the end connections of
the armature coils into the bottom of the machine, whence it passes
through the ventilating ducts of the core to an opening at the top. The
field core is, according to size, built up either of steel disks, each
in one piece, or of steel forgings, so as to give high magnetic
permeability and great strength. The coils are placed in radial slots,
thereby avoiding side pressure on the slot insulation and the complex
stresses resulting from centrifugal force, which, in these rotors, acts
normal to the flat surface of the strip windings.

Operation

As practically no adjustments are necessary when these units are in
operation, the greater part of the attention required by them is
involved in starting up and shutting down, which may be described in
detail as follows:

_To Start Up_

First, the auxiliary oil pump is set going, and this is speeded up until
the oil pressure shows a hight sufficient to lift the inlet valve and
oil is flowing steadily at the vents on all bearings. The oil pressure
then shows about 20 to 25 pounds on the "Relay Oil" gage, and 2 to 4
pounds on the "Bearing Oil" gage. Next the throttle is opened, without
admitting sufficient steam to the turbine to cause the spindle to turn,
and it is seen that the steam exhausts freely into the atmosphere, also
that the high-pressure end of the turbine expands freely in its guides.
Water having been allowed to blow out through the steam-chest drains,
the drains are closed and steam is permitted to continue flowing through
the turbine not less than a half an hour (unless the turbine is warm to
start with, when this period may be reduced) still without turning the
spindle. After this it is advisable to shut off steam and let the
turbine stand ten minutes, so as to warm thoroughly, during which time
the governor parts may be oiled and any air which may have accumulated
in the oil cylinder above the inlet valve blown off. Then the throttle
should be opened sufficiently to start the turbine spindle to revolving
very slowly and the machine allowed to run