MIL-DTL-3124E(SH)
4.6.19.1.1 Static analyses. Shock analyses of equipment not tested (see 3.4.17.1) shall be based on the
following minimum static shock factor values which apply at the bottom of mounting or feet.
Static shock factor
Application
Vertical
Athwartship
Fore and aft
Generator
75
45
20
4.6.19.1.2 Dynamic analysis. When specified (see 6.2), a concurrent dynamic analysis shall be conducted.
4.6.19.2 Nil-ductility. Nil-ductility tests shall be conducted in accordance with ASTM E208 (see 3.4.18).
Subject to the acceptance of NAVSEA, impact tests may be substituted when statistical data show correlation
between nil-ductility properties and impact values.
4.6.20 Voltage and current balance. Voltage and current balance measurements shall be taken as specified in
4.6.20.1 Voltage balance. The voltage balance test shall consist of simultaneous measurements of voltage of
each phase at an excitation which produces rated voltage in at least one phase. This may be a part of the no-load,
rated-voltage saturation data test. The voltage across each phase and field current and field voltage shall be
recorded.
4.6.20.2 Current balance. The current balance test shall consist of simultaneous measurements of current in
each phase at an excitation which produces rated current in at least one phase. This may be a part of the no-load
saturation data tests, if the generator is run as a synchronous motor, by increasing the field current until rated current
is produced, or this data may be obtained by short-circuiting the generator terminals and applying sufficient field
current to cause rated current to flow. The current per phase, field voltage, and field current shall be measured.
4.6.21 Three-phase and single-phase short circuits. Each of the following short circuit tests shall be conducted
with the generator initially at no-load, rated voltage, rated frequency, and under control of the voltage regulator:
a.
An abrupt three-phase short circuit.
b.
An abrupt single-phase short circuit between any two line terminals.
The short circuit shall be applied for a time not less than that determined by I2T = 180, where I is the sustained value
of line current on a per-unit basis. The generator field shall be at rated full load temperature. The test shall
demonstrate that the generator and associated excitation system meet the requirements of 3.4.5 and that normal
voltage is restored upon removal of the short circuit.
4.6.22 Open-circuit saturation. When specified, sufficient data to plot a no-load saturation curve shall be
obtained. Points for this curve shall be taken as follows: four below 60 percent of rated voltage; one between 60
and 90 percent; one at rated voltage; and three above rated voltage. Readings shall be taken with increasing values
of field current and, when it is necessary to reduce the field, it shall be reduced to zero and then increased to the
desired value. When taking the saturation curve, readings of the driving motor input at zero-field and at rated
voltage shall be measured.
4.6.23 Synchronous impedance. Sufficient data to plot a synchronous impedance curve shall be obtained. Six
readings from 150 percent rated current shall be measured.
4.6.24 Transient and subtransient reactance. Direct-axis transient and subtransient reactance tests shall be
performed in accordance with MIL-STD-705, and the values calculated.
4.6.25 Phase unbalance. The generator shall be loaded with a single-phase load connected line-to-line of
15 percent of continuous rated current at rated voltage and at a power factor not less than the rated power factor
(see 3.4.7.1).
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