MIL-STD-1399-300 Electric Power, Alternating CurrentThis military standard section establishes electrical interface characteristics for shipboard equipment utilizing AC electric power to ensure compatibility between user equipment and the electric power system. Characteristics of the electric power system are defined and tolerances are established, as well as requirements and test methods for ensuring compatibility of shipboard user equipment with the power system. The policies and procedures established by MIL-STD-1399 are mandatory. This section and the basic standard are to be viewed as an integral single document for use in the design and testing of electric power systems and user equipment.

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MIL-STD-1399-3008

FIGURE 2.  Frequency modulation.

3.3.4  Frequency transients.  A frequency transient is a sudden change in frequency that goes outside the frequency tolerance limits and returns to and remains within these limits within a specified recovery time (longer than 1 ms) after the initiation of the disturbance.

3.3.4.1  Frequency transient tolerance.  Frequency transient tolerance is the maximum permitted departure from nominal user frequency during transient conditions.  The frequency transient tolerance is in addition to the frequency tolerance limits.

3.3.4.2  Frequency transient recovery time.  Frequency transient recovery time is the time elapsed from the instant when the frequency first goes outside the frequency tolerance limits until the instant when the frequency recovers and remains within the frequency tolerance limits.

3.4  Voltage.  Units are in Volts (V).  Unless otherwise specified, voltages in this standard are root-mean-square

(rms) values.  Tolerances are expressed in percent of the nominal user voltage.

3.4.1  Nominal user voltage.  Nominal user voltage (Vnominal) is the designated voltage at the interface.

3.4.2  User voltage tolerance.  User voltage tolerance is the maximum permitted departure from nominal user voltage during normal operation, excluding transients and modulation.  User voltage tolerance includes variations caused by load changes, the environment (temperature, humidity, vibration, inclination), and drift.  Tolerances are expressed in percentage of nominal voltage.  The average line-to-line voltage tolerance is calculated in Equation 2 and the line-to-line voltage tolerance is calculated in Equation 3.  Voltages are either all rms or all peak (sinusoidal crest) values.

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Average line-to-line voltage tolerance (percent) = 1 Average voltage - Nominal user voltage 1x100

Where:

⎝           Nominal user voltage               ⎠

The average voltage is the sum of the line-to-line voltages divided by the number of line-to-line voltages and the nominal user voltage is provided in Table I, item 7.

EQUATION 2

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