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

5.3.6.2 Procedure. The user equipment shall be operated in accordance with the equipment operating procedure in one of the normal modes of operation. Power input voltage and frequency shall be within the user tolerance bands. Measure and record power input voltages (each phase), each line current, power factor for each phase, and power (kW). These measurements shall be made for each power input required from the electric power system. From the data collected during these tests, calculate and record the data elements specified in 5.3.6 for each user equipment power input. Surge/inrush current is discussed in 5.2.10 and limits are provided in Figures 21 and

22. The user equipment shall be de-energized and re-energized in accordance with the equipment operating procedures; surge/inrush current shall be measured, recorded, and evaluated when energizing the user equipment at the nominal input voltage for the following cases: when the voltage source sine-wave passes through 0 degrees (for inductive load equipment) and when the sine-wave passes through 90 degrees (for capacitive load equipment). The largest inrush current of the two cases shall be used. During this period of de-energizing and re-energizing, oscilloscope records shall be taken of one line voltage and each line current to determine surge/inrush current during the transition. The data recorded shall be of sufficient resolution to be able to accurately determine the magnitude and duration of the surge/inrush current. The power profile test shall be repeated for each normal operating mode and for each user equipment power input. All test values shall be within limits in accordance with the applicable requirements. The power source used for this test and its characteristics shall be reported in order to assist in analyzing the impact the equipment may have on a shipboard power system. The power source rating and its source impedance, as well as the length and type of connecting cable used, shall be included. Determine by measurement, calculation, or specification and record the value of the capacitance to ground for each power line of the user equipment. Line-to-ground capacitance limits are identified in 5.2.4. Determine by measurement, calculation, or specification and record the value of the line-to-ground current for each power line of the user equipment. Line-to- ground current limits are identified in 5.2.4.

5.3.7 Current waveform test. The harmonic content from nominal input line frequency up to 20 kHz of the current waveform in the user equipment power input lines shall be determined for each operating mode. The harmonic current of the user equipment shall be in compliance with the requirements in 5.2.9.

5.3.7.1 Apparatus. The following apparatus is recommended for performing this test:

a. Power source of required capacity and range of voltage and frequency adjustments. A power source with a capability of having an independently programmable voltage and frequency output is recommended.

b. Voltmeters (true rms) - ±0.5 percent accuracy. c. Frequency meter - ±0.5 Hz accuracy.

d. Ammeters.

e. Wide-band current probe or shunt.

f. Current and potential transformers and probes as required.

g. Harmonic analyzer with a better than 3 percent of measured frequency band width below 2.5 kHz and a less than 75 Hz band width at frequencies between 2.5 and 200 kHz.

5.3.7.2 Procedure. The user equipment shall be energized in accordance with the equipment procedure and operated in a normal mode. The power source voltage and frequency shall be within the applicable frequency and voltage tolerance envelopes shown in Figures 9 through 15. The power input current harmonics shall be determined for each operating mode. The current harmonics shall be measured by means of a wide-band current probe or shunt in each power input line. The fundamental and harmonics of each line current shall be measured by means of a harmonic analyzer. The current harmonics shall be determined for each normal operating mode and shall not exceed the values specified in 5.2.9. If it is suspected that the power source has sufficient voltage harmonic distortion to affect current harmonic measurements, to determine the baseline harmonic currents due to the source, connect a linear load (no larger than the user equipment load and having the same fundamental frequency leading or lagging power factor as the user equipment to be tested) at the power interface where the user equipment would be

connected. The harmonic currents shall be measured. These measured harmonic current values from the linear load may then be subtracted from the harmonic current values measured from the normally operated user equipment to provide an approximation of the equipment's harmonic current content.