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

5.2.10  Surge/inrush current.  User equipment shall be constructed to limit the ratio of surge current to normal operating current.  The ratio of the maximum surge/inrush peak current to the full nominal load rms current shall be limited to the value determined from Figure 21 for Type I, 60 Hz electric power and Figure 22 for Types II and III,

400 Hz electric power.  Load sequencing may be required to maintain an acceptable user voltage envelope at the

user interface.  Surge/inrush current shall be measured, recorded, and evaluated when energizing the user equipment at the nominal input voltage when the voltage source sine-wave passes through 0 degrees for inductive load equipment or when the sine-wave passes through 90 degrees for capacitive load equipment.  Multiple surge/inrush

current occurrences observed on the same event shall be addressed and evaluated individually to determine

compliance with the above requirements.

10

9

8

7

Type I

115 Vac

6

5

Type I

440 Vac

4

3

2

1

0

1                                                10                                              100                                            1000

Input Power (kW) Rating of User Equipment

Figure 21.  Surge current limits for load equipment using Type I power.

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