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.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 - 26 - 27 - 28 - 29 - 30 - 31 - 32 - 33 - 34 - 35 - 36 - 37 - 38 - 39 - 40 - 41 - 42 - 43 - 44 - 45 - 46 - 47 - 48 - 49 - 50 - 51 - 52 - 53 - 54 - 55 - 56 - 57 - 58 - 59 - 60 - 61 - 62 - 63 - 64

MIL-STD-1399-3008

FIGURE 7.  Voltage deviation factor variables.

3.5  Current.  Units are in Amperes (A).  Unless otherwise specified, currents in this standard are rms values.

3.5.1  Current unbalance.  Current unbalance for three-phase loads is the ratio of the maximum line current magnitude minus the minimum line current magnitude to the average of the three line current magnitudes in amperes, shown in Equation 8.  Currents used in the following equation are rms values.

§ Ilinemax − Ilinemin  ·

Current unbalance (percent) =  1 (I

I     I  )/3 1x100

⎝  A +

8 + C         ⎠

EQUATION 8

3.5.2  Current waveform.  The current waveform is a current vs. time function.

3.5.2.1  Current single harmonic.  A current single harmonic is a sinusoidal component of the current's periodic waveform having a frequency that is an integral multiple of the fundamental frequency.

3.5.2.2  Current single harmonic content.  The current single harmonic content of a current waveform is the ratio, in percentage, of the rms value of that harmonic to the rms value of the fundamental.

3.5.3  Surge/inrush current.  Surge current is a sudden change in line current to a user equipment that occurs during start-up or after a power interruption or as a result of a change to the operating mode.  Typically, the surge current will rise to a maximum value in a few milliseconds (msec) and decay to rated value in several msec to several seconds.

10