MAINTENANCE OF AC ELECTRICAL POWER GENERATION AND CONTROL SYSTEM
SECTION I. WIRING HARNESS OVERHAUL
5-1. GENERAL. Electrical interconnection of control devices and indicators is accomplished through wiring harnesses.
Wires in the harnesses are bundled and secured to prevent unnecessary movement and chafing, and to conserve space.
5-2. WIRING HARNESS OVERHAUL. If 30 percent of the wires in a harness are defective, it must be overhauled. FO-
15 through FO-32 are wiring harness fabrication drawings. These drawings specify the length and gage of every wire
used in each harness, as well as the termination points, lugs or connectors, and wire marking data. The harness
drawings also provide routing information for each harness.
SECTION II. MAINTENANCE OF GENERATOR G1
5-3. GENERAL. In the following discussion, "rear" of the generator is toward the engine.
A solid rolled steel frame provides support for the stator core and end bracket. Bar steel core supports, welded to the
core and frame, anchor the stator core.
The end bracket is made of cast iron and supports the stationary exciter field structure. The frame is fitted with a cast
iron machining adapter which aligns with the engine. An iron hub is keyed and heat shrunk to the shaft. This hub carries
ten flexible steel drive discs which have holes for fastening to the flywheel. Two spacers are used between the hub and
discs to maintain the proper distance between the discs and machining adapter face. This affords flexibility in the axial
direction, while in the radial direction it acts as rigid coupling, providing a uniform air gap.
The stator laminations are composed of thin, low-loss steel. The cores are reinforced by steel stack rings and supporting
bars which are welded around the core. When the insulated coils have been inserted in the stator core, the entire core is
given multiple dips and bakes in thermosetting varnish. This insulation system utilizes all synthetic and non-hygroscopic
materials making the windings fungus resistant and suitable for operation in high humidity and abrasive environments.
Subsequently, the wound core is placed into and welded to the frame.
The rotor pole assembly is heat shrunk and keyed to the shaft. A thermo-setting bond epoxy is applied between layers of
the field winding and is applied to the finished rotor. The completed rotor is baked under a controlled cycle. Rotors are
dynamically balanced and then tested at 125 percent of operating speed.
The ac exciter armature and the heat sink which carries the diodes are mounted on an assembly which is placed on the
generator shaft on the outboard side of the front generator bearing.
The generator employs a flow-through ventilation system. The cast aluminum alloy ventilating fan draws air through
louvers in the conduit box, over the main stator and exciter windings and exhausts it through ventilation screens on the
Two strip heaters provide heating for the generator when it is not in service to prevent moisture buildup. These are
powered by 240 V ac from an external source.
5-4. GENERATOR OR GENERATOR COMPONENTS DRYING PROCEDURES. Machines that have been idle for
some time in unheated and damp locations, may have "sweated" as a result of sudden changes in temperature or may
have become wet by accident. These should be dried out thoroughly before being put into service. The following are
recommended drying methods.
a. Space Heaters. Enclose the generator with a covering and insert heating units (space heaters, lamps, or coils
of steam pipe) to raise the temperature. Leave a hole at the top of the enclosure to permit the escape of moisture.
b. Forced Air. A portable forced air heater can be used by directing heat to the end of the generator opposite
the coupling and running the generator with no load and without excitation (this can be accomplished by removing the
regulator fuses). Heat at point of entry should not exceed 150OF (660C) at the bearing hub.
c. Insulation Testing. If It is necessary to dry out the generator, it is recommended that the unit be thoroughly
tested using the procedures specified in paragraph 5-6.