MIL-DTL-3124E(SH)
3.4.11 Prime movers. The generator shall operate with the following prime movers as specified (see 6.2):
a.
Steam turbine.
b.
Diesel engine.
c.
Gas turbine.
3.4.12 Overload. Each generator shall deliver 150 percent of rated current for 2 minutes (see 4.6.13.2).
3.4.13 Temperature limits. The temperature rises of the various parts of a generator shall not exceed the
maximum permissible temperature rises as specified in table III with rated continuous kilowatt load at rated power
factor on the generator.
3.4.14 Efficiency. The generator efficiency shall be as specified (see 6.2).
3.4.15 Exciter rating. The capacity of the exciter shall meet the load and overload requirements specified
herein.
3.4.15.1 Voltage buildup. Exciters intended for emergency use shall provide rapid, positive voltage buildup
under all initial starting conditions and for all normal shipboard operating conditions. Positive buildup shall be
obtained at all times regardless of the manner in which the set is shut down. Excitation and regulation equipment,
which requires the exciter residual magnetism to be reduced to and held at the minimum to meet performance
requirements, shall not be used without auxiliary field flashing or similar devices for positive buildup. Auxiliary
circuit devices shall be completely static (no relays) and fail-safe in operation. Acceptability shall be demonstrated
by testing with the associated generator, exciter, and voltage regulator (see 4.6.18).
3.4.15.2 Automatic voltage regulator. The automatic voltage regulator shall meet the requirements specified in
MIL-R-2729.
3.4.16.1 Deviation factor. The deviation factor of the open-circuit terminal voltage shall be not greater than
5 percent on any phase.
3.4.16.2 Harmonic content. From no load to full load, the harmonic content of the output voltage wave shall
meet the requirements of the table for Type I power of MIL-STD-1399-300. Harmonic content shall be measured as
specified (see 4.6.15.1).
3.4.17 Resistance to shock. The generator shall be shockproof in accordance with hull-mounted items, Grade
A, Class I, Type A of MIL-S-901. The generator shall meet the performance requirements of this specification
when subjected to the magnitude of shock specified for static and dynamic analyses, or that encountered during the
shock test, as applicable (see 4.6.19).
3.4.17.1 Shock test versus static and dynamic analysis. Equipment tested, by reason of weight and size not
exceeding the available facilities, shall be subjected to the shock test specified (see 4.6.19). Shock testing shall be
used to the maximum extent possible, and static and dynamic analysis shall be used where shock testing is
impracticable as approved by NAVSEA (see 4.6.19.1).
3.4.17.2 Use of static shock factor values. The equipment shall withstand shock loads due to steady
acceleration at the static shock factor values applied separately in each direction (plus or minus). Each mass element
of the unit shall have an inertia load applied equal to:
dm x G x g
Where:
dm = Distribution mass
G = Static shock factor value tabulated herein
g = Acceleration of gravity
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