[Illustration: PART OF BUS BAR COMPARTMENTS--MAIN POWER STATION]
[Sidenote: _Alternators_]
The alternators closely resemble those installed by the Manhattan
Railway Company (now the Manhattan division of the Interborough Rapid
Transit Company) in its plant on the East River, between 74th Street
and 75th Street. They differ, however, in having the stationary
armature divided into seven castings instead of six, and in respect to
details of the armature winding. They are three-phase machines,
delivering twenty-five cycle alternating currents at an effective
potential of 11,000 volts. They are 42 feet in height, the diameter
of the revolving part is 32 feet, its weight, 332,000 pounds, and the
aggregate weight of the machine, 889,000 pounds. The design of the
engine dynamo unit eliminates the auxiliary fly wheel generally used
in the construction of large direct-connected units prior to the
erection of the Manhattan plant, the weight and dimensions of the
revolving alternator field being such with reference to the turning
moment of the engine as to secure close uniformity of rotation, while
at the same time this construction results in narrowing the engine and
reducing the engine shafts between bearings.
[Illustration: REAR VIEW OF BUS BAR COMPARTMENTS--MAIN POWER STATION]
[Illustration: DUCT LINE ACROSS 58TH STREET 32 DUCTS]
Construction of the revolving parts of the alternators is such as to
secure very great strength and consequent ability to resist the
tendency to burst and fly apart in case of temporary abnormal speed
through accident of any kind.
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