MIL-STD-1399 Section 300 Part 1 — Summary and Acceptance Criteria

Established in 2018, MIL-STD-1399-300-1 establishes mandatory AC electrical interface requirements to ensure compatibility between user equipment and shipboard AC power systems. It defines the power characteristics, tolerances, and required compliance tests for equipment connected to Navy AC power systems.

The standard covers three system types:

• Type I: 115/440 Vrms, 60 Hz (primary ship service distribution)
• Type II: 115/440 Vrms, 400 Hz, ungrounded
• Type III: 115/440 Vrms, 400 Hz, ungrounded, with tighter tolerances

It includes mandatory grounding, current waveform limits, surges, spikes, pulsed load behavior, and numerous susceptibility tests (voltage/frequency tolerance, spike, emergency conditions, AGD, insulation, etc.). Table I lists all required compliance tests.

This article provides an overview of the standard and makes references to sections and figures that are found within the document. You may download a copy of the standard  from the DLA quick-search site.  and download the standard from this page. 

If you are looking for MIL-STD-1399 compliant power supply, ETA-USA offers Type I, 60Hz compliant models available in 500~2400W on its Military and Aviation page. 

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POWER SYSTEM TYPES AND CHARACTERISTICS

Type I — 60 Hz Power (Primary Shipboard AC Power)

Definition: 115 or 440 Vrms, 60 Hz; ungrounded or high-resistance grounded (440 V) or solid-grounded (115 V).

Applications: Standard ship service and lighting loads.

Type I System Characteristics (Table II Extracts)

• Voltage tolerance: ±5% steady state (115 V or 440 V)
• Frequency tolerance steady state: 60 Hz ± 2% (59–61.2 Hz)
• Transient tolerances: defined envelopes (Figure 10) including excursions during faults and switching operations.
• Harmonics:
  • THD ≤ 5%
  • Single harmonic ≤ 3%
  • Deviation factor ≤ 5% (3% for submarines)
• Spike voltage: 900–1000 V peak (115 V systems) per Table V.
• Emergency conditions:
  • Frequency excursion −100% to +12%
  • Voltage excursion −100% to +35%
  • Duration up to 2 minutes depending on case

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Type II — 400 Hz Ungrounded

• Limited-use system with wider tolerances than Type III.
• Behavior of power decay is fast due to M/G set protective trip actions (interruptions occur within ms).

Type III — 400 Hz Ungrounded (Tighter Tolerances)

• Used where precision 400 Hz is needed (avionics).
• Tighter steady-state and transient tolerances than Type II.
• Delivered typically as 115/200 V 400 Hz grounded-wye for aircraft servicing.

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USER EQUIPMENT REQUIREMENTS (APPLICABLE TO ALL TYPES)

All equipment must comply with section 5.2. requirements, enforced through tests in Section 5.3.

Major required attributes:

Voltage & Frequency Compatibility

Equipment must tolerate all defined Type-specific envelopes (steady-state, transient, emergencies).

Current Harmonic Limits (Very Important for Power Supplies)

For 60 Hz equipment ≥1 kVA (your 1000 W AC/DC supply qualifies):

• From 60 Hz–2 kHz: ≤3% of fundamental current
• From 2 kHz–20 kHz: ≤(6000 / f)%
  (Figure 22)

For <1 kVA equipment: similar but slightly more lenient (Figure 23).

Power Factor Requirement

• PF must meet criteria of 5.2.7.
• Corrective action may be required for poor PF loads.

Inrush / Surge Current

The ratio of surge to rated current is limited by a curve (Figure 26).
Measured at specific AC zero-crossings.

Pulsed Load Requirements

Applicable to loads that switch or step power.

• Must meet time-domain and frequency-domain limits.
• TSD calculations must follow Appendix A.

Grounding and Leakage Current Limits

Includes:

• Insulation resistance tests
• Active ground detection (AGD) support
• Simulated human-body ground-current tests (Figures 33–37)

Voltage Spike Survival

Equipment must survive spike tests:

• 900–1000 V peak for 115 V systems
• Sync angles: 0°, 90°, 180°, 270° on all conductors

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REQUIRED COMPLIANCE TESTS

Table I lists all required tests by requirement category.
Major tests include:

• Grounding test (5.3.1)
• Power profile verification (phases, voltage, PF, current) (5.3.2)
• Voltage & frequency tolerance test (5.3.3)
• Transient tolerance test (5.3.4)
• Voltage spike test (5.3.5)
• Emergency conditions test (4 subtests: tr, ts, decay, excursion) (5.3.6)
• Current waveform (harmonics) test (5.2.10 / 5.3.7)
• Modulation susceptibility test (5.3.8)
• Human-body leakage current tests (5.3.9)
• Line-to-ground withstand & AGD tests (5.3.10)

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115 VAC, 60 Hz, SINGLE-PHASE (TYPE I) IN DETAIL

The criteria for a single phase, 115Vac nominal AC/DC power supply described below outlines the acceptable criteria for a

Applicable System Characteristics (Table II for Type I)

For 115 Vrms 60 Hz Type I power, your supply must:

Voltage Characteristics

• Nominal: 115 Vrms
• Steady-state tolerance: ±5%
• Transient tolerance envelope defined in Figure 10 (frequency & voltage).
• Emergency voltage excursions: −100% to +35% for up to 2 minutes.

Frequency Characteristics

• Nominal: 60 Hz
• Steady-state tolerance: ±2% (58.8–61.2 Hz)
• Transient: tight envelope defined in Figure 10.

Harmonics and Waveform

• THD ≤ 5%
• Individual harmonic ≤ 3%
• Deviation factor ≤ 5%

Required Equipment Performance Requirements

Harmonic Current Limits (≥1 kVA Applies to Your 1000 W Converter)

Per 5.2.10 and Figure 22:

• ≤3% of fundamental (60–2,000 Hz)
• ≤6000/f % (2 kHz–20 kHz)

Inrush Current Limits

Must satisfy the surge/inrush envelope of Figure 26.

Voltage Spike Survival

Equipment must withstand:

• 900–1000 V peak spikes on all conductors
• At 0°, 90°, 180°, 270°

Emergency Condition Survival

Equipment must endure:

1. tr limited-break interruption (~70 ms if unknown)
2. ts emergency source transfer interruption
3. Power decay behavior (loss of prime mover)
4. Positive voltage excursion

Ground Detection Requirements

If installed on ships using AGD:

• Must pass AGD susceptibility test (DC source applied through RAGD = 50 kΩ).
• Single-phase AGD test circuit shown in Figure 39.

Insulation Resistance

Verified via megohmmeter per 5.3.10.1.

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Acceptance Criteria Summary (What Your 115 V 60 Hz Power Supply Must Pass)

Your AC/DC power supply must pass all of the following to be MIL-STD-1399-300-1 compliant:

Electrical Compatibility

• Operates over full voltage & frequency tolerance and transient envelopes
• Survives all emergency condition subtests (tr, ts, decay, excursion)

Waveform Quality

• Input current harmonics within Figure 22 limits
• PF meets 5.2.7

Safety / Grounding

• Leakage current within limits of 5.2.5 (human-body impedance tests)
• AGD and L-G withstand tests passed

Transient Robustness

• Survive specified voltage spikes (900–1000 V peak)

Operational Behavior

• Inrush current within Figure 26 limits
• Pulsed/ramped load limits if applicable
• No excessive line-to-ground capacitance or current (5.2.4)

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Additional Compliances 

In addition to the requirements outlined in 1399, the qualifying power supply must meet applicable sections of MIL-STD 461 (version dictated by the government procurement office, but the most current version is 461G). At the very least, expect conducted emissions CE101 & CE102; radiated emissions RE101 & RE102; conducted susceptibility  CS101, CS114, CS115. The supply may also need to perform with the limits of radiated susceptibility of RS101 and RS103. 

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Mil-Std 1399 Power supplies For Purchase

ETA-USA offers military grade power supplies with customizable options that meet Mil-std 1399 Sec 300 Part 1 60Hz single phase requirement.  Contact an ETA-USA representative for price, lead-time, and CADS.  All ETA-USA power supplies ate TAA compliant and Mil-grade products are made in the USA.

Customizable AC/DC Mil-grade Power Supplies

CH-M500    DATASHEET

CH-M1000  DATASHEET

CH-M2000  DATASHEET

Mil-S-901 Compliant IP66 Rated AC/DC Power Supplies

LPM500  DATASHEET

LPM650  DATASHEET

LPM1100  DATASHEET