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

5.2.8 Ramp load. Ramp loading shall be limited to an average of 30 percent of source rating in kVA per second. No step shall be greater than that specified for pulsed loads (see 5.2.7).

5.2.9 Input current waveform. The operation of user equipment shall cause minimum distortion on the electrical distribution system current waveform. Harmonic current and other conducted emissions (within the 20 kHz frequency band) introduced by the load are limited in order to allow the source and distribution system to maintain the bus voltage distortion within specified limits. Single frequency limits for 60 Hz and 400 Hz user equipment at the nominal user voltage levels of Table I are depicted in Figures 17, 18, 19, and 20. The criteria defined in Figures 17 and 18 are similar to the MIL-STD-461 limit criteria for the EMI test CE101 for 60 Hz fundamental tailored to 20 kHz. Harmonic current shall be measured at nominal voltage input for all operating modes.

5.2.9.1 60 Hz user equipment greater than or equal to 1 kVA. The operation of user equipment or the aggregate with power ratings > 1 kVA shall not cause single harmonic line current or current of any frequency above the fundamental at 60 Hz to 2000 Hz to be generated that is greater than the limit line set at 3 percent of the unit's full rated load fundamental current. Additionally, harmonic line current or current of any frequency above

2000 Hz through 20 kHz shall not exceed the limit line set at 6000/f percent of the user equipment's full load fundamental current, where f is the nominal frequency. This is shown in Figure 17. User equipment, for the purposes of this requirement, shall be defined as a system with a standalone unit or the aggregate of a system with

multiple like units on a single bus, e.g. lighting source power supplies. The rating of equipment with multiple power

inputs from the same interface shall be the summation of all the power inputs under steady-state conditions.

FIGURE 17. Limit line for currents at frequencies greater than 60 Hz for equipment greater than or equal to 1 kVA.