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

5.1.6.2 System voltage. System voltages are as follows (see 5.2.2):

a. 440 Vrms, 3-phase (ungrounded). b. 115 Vrms, 3-phase (ungrounded).

c. Special service, 115/200 Vrms, 3-phase, 4-wire, grounded neutral, 400 Hz power is provided for servicing aircraft in hangars and on flight decks, and to avionics shops.

d. Special service, 115/200 Vrms, 3-phase, 4-wire, grounded neutral, 60 Hz power is provided for avionic shops.

e. Special service, 230 Vrms, 60 Hz, 3-phase, ungrounded or 230 Vrms, 60 Hz, single-phase, grounded or ungrounded. This power is provided upon request only for NATO load equipment.

f. Special service, 120/208 Vrms, 60 Hz, 3-phase, 4-wire, grounded neutral or 240/120 Vrms, 60 Hz, single- phase, grounded neutral. These special distribution system voltages shall be in accordance with NAVSEA Standard Drawing 7512881 and NAVSEA Standard Drawing 7598285, respectively.

5.1.6.2.1 Type I, 60 Hz and Type II, 400 Hz power voltage transient. Figure 12 illustrates the 440 Vrms Type I, 60 Hz and Type II, 400 Hz voltage transient and user voltage tolerance envelope specified in Table I. Figure 13 illustrates the 115 Vrms, Type I, 60 Hz and Type II, 400 Hz, worst case voltage excursion and user voltage tolerance envelope specified in Table I. Voltage transients of 10 percent or less may occur several times an hour, and voltage transients of 10 to 16 percent may occur several times a day (percentages based on nominal user voltage). The time to reach the transient maximum may vary from 0.001 to 0.03 seconds, or to reach the transient minimum may vary from 0.001 to 0.06 seconds on Types I and II power systems, depending on the rating of the generator and the type regulator and excitation system employed. The sudden application of user equipment to the Type I or II electric power system may cause the voltage to decrease to the transient voltage minimum value within 0.001 to 0.06 seconds. The voltage may then increase to a maximum value that is above the nominal voltage by an amount equal to ⅓ to ⅔ of the minimum transient voltage drop at a rate equal to 20 to 75 percent of the nominal voltage per

second. Recovery to within the user voltage tolerance envelope will occur within 2 seconds. The sudden removal of user equipment from the electric power system may cause the voltage to increase to the transient voltage maximum within 0.001 to 0.03 seconds. The voltage may then decrease to a minimum value that is below the nominal voltage by an amount equal to ⅓ to ⅔ of the maximum transient voltage rise at a rate equal to 20 to 75 percent of the

nominal voltage per second. Recovery to within the user voltage tolerance envelope will occur within 2 seconds.