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

NOTE: Equipment utilizing non-standard power should not be used at voltages sourced by a line-to-line wye that are greater than 220 Vrms nominal or at frequencies that are greater than 60 Hz nominal as the human body leakage current measured in the Simulated Human 8ody Leakage Current Test in 5.3.9 will exceed the limit even though the equipment may be utilizing a filter containing the maximum allowable capacitance to ground of 0.1 uF. The two phase voltages producing the line-to-line voltage are separated by 120 degrees, not 180 degrees and do not sum to zero; the resultant voltage will produce a corresponding current.

5.2.4.1.1 Low frequency human body leakage current limits for personnel safety. Low frequencies include the input power fundamental and harmonics up to 700 Hz. The current limit through the impedance network simulating the human body for the test in 5.3.9 for the low frequency range is 5 milliamperes.

5.2.4.1.2 High frequency human body leakage current limits for personnel safety. High frequencies include those greater than 700 Hz and less than 100 kHz. The requirement to conduct a high frequency test shall be determined from an evaluation of the conversion technology (switching frequency) included in the equipment design. Any power-switching converter operating at a frequency above 1 kHz shall be tested. The current limit through the impedance network simulating the human body for the test in 5.3.9 for the high frequency range is 70 milliamperes.

5.2.5 Current (load) unbalance. User equipment comprised of a combination of single-phase and three-phase loads shall have a resulting input three-phase line current unbalance not exceeding 5 percent (submarines 3 percent) of the user equipment rating under normal operating conditions and during normal operating modes. This shall be measured with a voltage source having a line voltage unbalance less than 1 percent. Three-phase current unbalance shall be calculated as defined in 3.5.1. This requirement does not apply to aircraft servicing systems that are designed for a maximum current unbalance of 15 percent of the user equipment rating.

5.2.6 User equipment power factor. User equipment shall operate within the user frequency and voltage tolerance envelope of Figures 9 through 15 as applicable with a pf within the range of 0.8 lagging to 0.95 leading for

60 Hz and 0.8 lagging to 0.9 leading for 400 Hz under normal steady state operating conditions, excluding start-ups and pulsing loads.