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

5.3.8.2 Procedure. The user equipment to be tested shall be operated in a normal operating mode within the user voltage and frequency tolerance band until the equipment temperatures have stabilized. Temperature stability shall be defined as when the variation between successive temperature measurements at the same location does not exceed 1 °C after 30 minutes. The voltage and frequency modulation test produces a voltage and frequency modulation on the input waveform from nominal to within the modulation limits defined by Table VII for the applicable power type. The input voltage and frequency shall be varied separately and then simultaneously. The input voltage (at least two phases for three-phase power equipment), input line current (at least two line currents for three-phase equipment), and frequency shall be recorded before initiation of modulating voltage and frequency and continue throughout each test run.

a. Voltage modulation test: With the frequency held constant at nominal, vary the voltage from minimum to maximum for periods of 17 msec, 75 msec, 250 msec, 500 msec, 1 second, 5 seconds, and 10 seconds. Repeat each cycle of modulation ten consecutive times before moving to the next modulation period, starting at 17 msec and ending at 10 seconds.

b. Frequency modulation test: With the voltage held constant at nominal, vary the frequency from minimum to maximum for periods of 17 msec, 75 msec, 250 msec, 500 msec, 1 second, 5 seconds, and 10 seconds. Repeat each cycle of modulation ten consecutive times before moving to the next modulation period, starting at 17 msec and ending at 10 seconds.

c. Combined voltage and frequency modulation test: Simultaneously vary the voltage from minimum to maximum and the frequency from minimum to maximum for periods of 17 msec, 75 msec, 250 msec, 500 msec, 1 second, 5 seconds, and 10 seconds. Repeat each cycle of modulation ten consecutive times before moving to the next modulation period, starting at 17 msec and ending at 10 seconds.

The user equipment shall operate normally with no operational degradation during all test conditions to show compliance with this test. The recording quality shall be sufficient to show that the proper modulation limits were conducted.

5.3.9 Simulated human body leakage current tests for personnel safety.

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

a. Operational circuit configuration defined by Figure 28 for single-phase systems, by Figure 29 for single- phase systems derived from line-to-line of a three-phase wye and by Figure 30 for three phase systems.

b. Metering circuit defined by Figure 31 for low or high frequency operation.

c. Power source defined by the circuit configuration as either a single-phase center-tapped source or a three- phase wye source of required capacity determined by the Unit Under Test (UUT). The line voltage unbalance shall be less than 3 percent.

d. Voltmeter should be true rms of +0.5 percent accuracy; the frequency response should be within measurement requirements.

e. Insulated probe, such as an oscilloscope probe.

5.3.9.2 Procedure. With power disconnected, place the user equipment or UUT on an isolated surface. The UUT shall be isolated from any earth, power, or instrument ground. Single-phase user equipment shall be connected as in Figure 28 if it operates connected across one single-phase (line-to-line of a delta source or line-to-neutral of a wye source) of a three-phase transformer aboard ship. Alternately, single-phase user equipment shall be connected

as in Figure 29 if it operates connected across two phases (line-to-line of a wye source) of a three-phase transformer aboard ship. Three-phase user equipment shall be connected as in Figure 30. The appropriate metering circuit shall be used for the intended frequency range, shown in Figure 31. Every mode of operation shall be tested. The current shall be determined by measuring the voltage drop across the metering circuit. The voltage measured across the metering circuit, when equal to 1.0 Vrms, represents 2.0 milliamperes of current. The overall measurement error shall not exceed 5 percent. Where there is risk for current paths to any control or external surface component, the insulated probe shall be used on all control or external surface components such as case, connector housings, recessed calibration or adjustment controls and control shafts with knobs removed.