MIL-STD-1275F: 28 VDC military vehicle power
Equipment that draws 28 VDC from a US military ground vehicle is specified against MIL-STD-1275F, dated 7 September 2022, which superseded MIL-STD-1275E of 22 March 2013. It is a short interface standard (21 pages in ASSIST) with five requirement blocks: steady-state range and ripple, engine starting, spikes, surges and reverse polarity, each injected into the equipment and, for ripple, spikes and surges, also measured as emissions from it. This page gives every limit and test parameter from the text of 1275F, a parameter table comparing revisions D, E and F, how the standard uses MIL-STD-461 and ISO 7637-2, how it differs from MIL-STD-704, and the common readings that the text contradicts, including several this page used to make.
What the standard covers, and what it does not
Section titled “What the standard covers, and what it does not”The scope paragraph of 1275F defines "the operating voltage limits and transient voltage characteristics of the 28 VDC electrical power at the input power terminals to the utilization equipment connected to the electrical power distribution system on military ground vehicle platforms". The foreword adds three points that shape every contract:
- It is an equipment standard. "This is neither a power source nor a power system standard." It covers utilization equipment, the conditions it must operate under and, new wording in F, "its permitted emissions".
- The vehicle is responsible for the bus. The vehicle design authority must ensure that the 28 VDC delivered to the equipment terminals meets the standard.
- EMI and ESD are out. Paragraphs 4.2 and 4.3 require compatibility with the applicable EMI and ESD requirements but state that neither is covered; 5.3.5 and 5.3.6 require that compliance to be shown before MIL-STD-1275 testing.
The standard names no vehicle families. It applies where a contract or performance specification calls it up. Paragraph 6.3 notes that certain provisions are the subject of NATO STANAG 2601.
Every requirement in MIL-STD-1275F
Section titled “Every requirement in MIL-STD-1275F”"Operate" in the table means the text's own wording: "operate without degradation or damage". In the verification methods, "any deviation from normal operation shall be recognized as a failure of the EUT".
| Clause | Requirement | Limit in 1275F | Test method (clause 5.3) |
|---|---|---|---|
| 5.1.1.1 | Operational voltage range | 20 VDC (lower limit of Figure 8) to 33 VDC, ripple included | Operate across the range |
| 5.1.1.2.1 | Injected ripple | Up to 2 V above and below the steady state (4 V peak to peak), 30 Hz to 5 kHz | MIL-STD-461 CS101 method at 22 VDC and 31 VDC |
| 5.1.1.2.2 | Emitted ripple | Less than 1 V above and below (2 V peak to peak), 30 Hz to 1 kHz | Through a source resistor and LISN at 22 and 31 VDC, each load condition at least 10 s, oscilloscope FFT or spectrum analyser |
| 5.1.2.1 | Initial engagement surge (starting) | Minimum 12 VDC, maximum 1 s | Table I sequence: 20 V 1 s, 12 V 1 s, repeated, last 12 V step followed by 16 V for 30 s |
| 5.1.2.2 | Cranking | Minimum 16 VDC, maximum 30 s | Same sequence; consecutive starting events at least 1 s apart |
| 5.1.3.1.1 | Injected spikes | Within Figure 7 (plus or minus 250 V up to 70 µs, narrowing to 100 V and 18 V at 1 ms); rise time 50 ns maximum; energy 200 mJ maximum per spike | At least 50 spikes of 250 V per polarity, 1 s apart, ringing above 20 kHz and below 500 kHz, through a LISN at 28 VDC, at worst-case load |
| 5.1.3.1.2 | Emitted spikes | Within Figure 7; 125 mJ maximum per event | ISO 7637-2 conducted transient emission method; each switching function at least 32 times, 1 s apart |
| 5.1.3.2.1 | Injected surges | Within Figure 8: 100 V up to 50 ms, back to 33 V by 500 ms; low side 18 V up to 500 ms, back to 20 V by 600 ms; 500 mΩ source | Table II: 30 V operating, 100 V peak, rise 1 to 10 ms, switch 1 closed 50 ms, switch 2 closed 500 ms, 500 mΩ, 5 pulses 5 s apart |
| 5.1.3.2.2 | Emitted surges | Within Figure 8 | Each surge-producing function at least 32 times |
| 4.1, 5.3.4 | Reverse polarity | Reverse current no greater than normal operating current; no damage | 33 VDC reversed for 5 minutes, then normal operation verified |
Two definitions decide which row applies to an event: a spike lasts 1 ms or less and is energy limited (3.7.2); a surge lasts more than 1 ms, typically with a fast edge and slow exponential decay (3.7.3). The alternator load dump is the standard example of a positive surge. Intermittent contact (relay chatter, contact bounce) is defined in 3.7.4 but carries no numeric limit of its own.
Verification conditions
Section titled “Verification conditions”| Item | 1275F value |
|---|---|
| Ambient | +23 °C plus or minus 5 °C, 0 to 90 % relative humidity, 80 to 102 kPa |
| Nominal voltage | Stated voltage plus or minus 1 % |
| Default measurement tolerance | Plus or minus 5 % (1275E: plus or minus 1 %) |
| Power supplies | Hold plus or minus 1 % of the set voltage at their output |
| Measurement point | EUT power input terminals; all inputs monitored individually and simultaneously |
| Waveform check | Injected waveforms verified open circuit before test |
| Power return | As the performance specification requires; chassis return simulated with a MIL-STD-461 ground plane |
| LISN count | One when the chassis is the return, two with a dedicated return conductor |
| Loads | Representative of the vehicle installation when the EUT is not standalone |
| Calibration | Traceable to a national standards body such as NIST |
Revision history from the ASSIST record
Section titled “Revision history from the ASSIST record”| Revision | Date | Notes from the texts |
|---|---|---|
| A | 17 September 1976 | Change Notice 1, 8 February 1980; Change Notice 2, 23 April 1981. Titled "Characteristics of 28 volt DC electrical systems in military vehicles" |
| B | 20 November 1997 | Validated by Notice 1, 20 April 2004 |
| C | 23 June 2006 | Superseded two months later |
| D | 29 August 2006 | Vehicle-level modes (normal, generator-only, battery-only); validated by Notice 1, 23 August 2011 |
| E | 22 March 2013 | Retitled "...input power to utilization equipment"; the modes disappear and one set of equipment limits replaces them; no marginal change marks "due to the extent of the changes" |
| F | 7 September 2022 | Current. Explicit ripple limits, emitted ripple added, spike energy and setup changes (table below). Next review due 6 September 2027 |
The ASSIST record starts at Revision A; no earlier basic issue is listed there.
What changed across D, E and F
Section titled “What changed across D, E and F”| Parameter | 1275D (2006) | 1275E (2013) | 1275F (2022) |
|---|---|---|---|
| Steady state | 25 to 30 V normal mode; 23 to 33 V generator-only | 20 to 33 V | 20 to 33 V |
| Initial engagement surge | Not below 6 VDC, 1 s maximum | 12 VDC minimum, 1 s maximum | 12 VDC minimum, 1 s maximum |
| Cranking | Not below 16 VDC; up to three 30 s attempts with 2 minute pauses | 16 VDC minimum, 30 s maximum | 16 VDC minimum, 30 s maximum; Table I gives the test sequence |
| Injected ripple | Within 2 V of the limits (7 V generator-only), 50 Hz to 200 kHz, SAE J1113-2 method | MIL-STD-461 CS101 limits, 150 kHz values extended to 250 kHz, tested at 23 and 30 VDC | 2 V above and below (4 V peak to peak), 30 Hz to 5 kHz, CS101 method at 22 and 31 VDC |
| Emitted ripple | No separate equipment limit; equipment must not push the system outside its limits (5.2) | Not specified | Under 2 V peak to peak, 30 Hz to 1 kHz |
| Injected spike energy | 15 mJ | 2 J | 200 mJ |
| Spike ringing frequency | 100 to 500 kHz | 100 to 500 kHz | 20 to 500 kHz |
| Positive surge | +40 V 50 ms from 20 mΩ (normal mode), +100 V 50 ms from 500 mΩ (generator-only) | 100 V, 50 ms, 500 mΩ, 60 J maximum | 100 V, 50 ms, 500 mΩ, set with two solid state switches (50 ms and 500 ms) |
| Emitted spike method | Exported spike test circuit in the standard (Figure 9) | SAE J1113-42 | ISO 7637-2 (third edition) |
| Reverse polarity | Protection against polarity reversal required | 33 VDC for 5 minutes; current limit in 4.1 | Same, with the current criterion repeated in the test method |
| Temperature | Limits determined from -32 °C to +52 °C (plus or minus 2 °C) | +23 °C plus or minus 5 °C | +23 °C plus or minus 5 °C |
Two consequences for programs. First, an E report does not show F compliance for emitted ripple, which E did not require, nor for the lower ripple test voltages (22 and 31 VDC instead of 23 and 30 VDC). Second, 1275F was written against MIL-STD-461G: it cites "MIL-STD-461G A.4.3.1" for setup tolerances and "A.5.5" for spectrum analyser corrections. MIL-STD-461H, dated 17 April 2026, is now current (see the MIL-STD-461 and MIL-STD-464 guide); clause 2.2.1 of 1275F leaves the MIL-STD-461 issue to the solicitation or contract, so the test procedure should state which one applies.
How MIL-STD-1275F uses MIL-STD-461 and ISO 7637-2
Section titled “How MIL-STD-1275F uses MIL-STD-461 and ISO 7637-2”| Cited document | Where | What for |
|---|---|---|
| MIL-STD-461 (issue per contract) | 2.2.1, 5.2.6 | Ground plane when the vehicle structure is the power return |
| MIL-STD-461 CS101 | 5.3.1.2.1 | Test method to inject the 4 V peak-to-peak ripple; the limit is set by 1275F, not by the CS101 curve |
| MIL-STD-461G A.4.3.1 | 5.3.3.1.1, 5.3.3.2.1 | Tolerances of the spike and surge test circuits |
| MIL-STD-461G A.5.5 | 5.3.1.2.2 | Correction factors when a spectrum analyser replaces the oscilloscope for emitted ripple |
| ISO 7637-2, third edition | 2.3, 5.3.3.1.2 | Conducted transient emission measurement for emitted spikes |
MIL-STD-461 CS106 does not appear in 1275F. That method was added in 461F and deleted in 461G, so a 1275 report has nothing to say about it.
MIL-STD-1275 and MIL-STD-704 side by side
Section titled “MIL-STD-1275 and MIL-STD-704 side by side”| Item | MIL-STD-1275F | MIL-STD-704F with Change 1 |
|---|---|---|
| Platform | Military ground vehicles | Aircraft |
| Current issue (ASSIST) | F, 7 September 2022 | F, 12 March 2004; Change 1, 5 December 2016; Notice 4 validation, 24 June 2026 |
| Systems | 28 VDC | 115 V AC 400 Hz (and variable frequency, 60 Hz), 270 VDC, 28 VDC |
| 28 VDC normal steady state | 20 to 33 V | 22.0 to 29.0 V |
| 28 VDC ripple | 4 V peak to peak injected | 1.5 V maximum ripple amplitude |
| Voltage spikes | Covered (Figure 7, 250 V) | "Not covered by this standard" |
| Test methods | In the standard (5.3) | MIL-HDBK-704-1 to -8 |
The two are not interchangeable: an aircraft power characteristic says nothing about engine cranking on a vehicle bus, and 704 leaves spikes to the EMI requirements.
Civil and allied counterparts
Section titled “Civil and allied counterparts”- ISO 16750-2:2023 (electrical loads for road vehicles, 12 V and 24 V systems) is the civil reference for supply voltage, overvoltage and superimposed alternating voltage. MIL-STD-1275F does not cite it; only ISO 7637-2 is called up, for emitted spike measurement.
- DEF STAN 61-005 Part 6 is the UK Ministry of Defence standard for 28 V DC electrical systems in military vehicles. Reseller catalogues list Issue 7 of March 2020; we could not reach the official UK Defence Standardization record to confirm its current status, so check it there before citing it in a contract.
Design consequences that follow from the text
Section titled “Design consequences that follow from the text”These are direct readings of the limits, not extra requirements:
- Clamp level. Spikes of 250 V and surges of 100 V for 50 ms must be passed with no degradation. A clamp that conducts during the 100 V surge must absorb energy from a 500 mΩ source for up to 50 ms, which is a very different rating from the 200 mJ single-spike case.
- Starting. If the equipment has to operate during engine start (5.3.2 says "when applicable"), the input stage must run at 12 V for 1 s and at 16 V for 30 s.
- Reverse polarity. The pass criterion is a current limit: reverse current must not exceed the normal operating current at 33 V for 5 minutes. A shunt diode that conducts heavily until a fuse opens does not meet it; a series blocking element does.
- Emissions. Since F, the equipment itself is limited to 2 V peak-to-peak ripple (30 Hz to 1 kHz), 125 mJ spikes and Figure 8 surges back onto the bus. Switch-mode front ends and inductive loads controlled by the equipment are the usual sources.
Claims the texts contradict
Section titled “Claims the texts contradict”| Claim | What the text says |
|---|---|
| "MIL-STD-1275E (2013) is the current revision" (this page said so) | ASSIST: Revision F, 7 September 2022, is current and supersedes E |
| "A 1971, B 1976, C 1992, D 2006" (this page said so) | ASSIST: A 17 September 1976, B 20 November 1997, C 23 June 2006, D 29 August 2006 |
| "The 100 V spike test" and "250 V surges" (this page said so) | 250 V events are spikes (1 ms or less); 100 V events are surges of 50 ms (3.7.2, 3.7.3, Table II) |
| "Cold start drops to about 6 V" (this page said so) | 6 VDC was the 1275D limit; E and F set 12 VDC for at most 1 s, then 16 VDC for at most 30 s |
| "Spikes must only be survived, not operated through" (this page said so) | 5.1.3.1.1: operate without degradation or damage; any deviation during the test is a failure |
| "Mission-critical and non-critical acceptance categories" (this page said so) | No such categories exist; 5.3.2 tests starting "when applicable" and the performance specification defines normal operation |
| "E formalised a slow turn-off envelope" (this page said so) | Neither E nor F contains a slow turn-off requirement |
| "A transient band up to +40 V" (this page said so) | +40 V was the 1275D normal-mode surge; E and F have one surge envelope with a 100 V peak |
| "Reverse polarity must be survived indefinitely" (this page said so) | 33 VDC reversed for 5 minutes, with reverse current no greater than normal operating current |
| "Steady state roughly 20 V to 33 V, outside it the equipment may shut down" | 20 to 33 V including ripple is the operating range; Figure 8 marks below 20 V as "may be inoperable" and above 33 V as "may be damaged" outside the surge envelope |
| "MIL-STD-1275 is the vehicle bus specification" | Foreword: neither a power source nor a power system standard; it states what the vehicle must deliver to equipment terminals |
Practical test plan
Section titled “Practical test plan”- Confirm the revision and the MIL-STD-461 issue cited in the contract, and whether starting operation applies to the equipment.
- Show EMI and ESD compliance first, as 5.3.5 and 5.3.6 require.
- Run the operational range, injected ripple at 22 and 31 VDC, and the Table I starting sequence.
- Verify spike and surge waveforms open circuit, then inject 50 spikes per polarity and 5 surges at worst-case load (or at minimum and maximum load when worst case is unclear).
- Measure emitted ripple, spikes and surges with every relevant function exercised (10 s per load condition for ripple, 32 operations for spikes and surges).
- Finish with reverse polarity, measuring the reverse current, then verify normal operation.
See also
Section titled “See also”- MIL-STD-461 and MIL-STD-464, defense EMC standards: radiated and conducted EMC framework for the same platforms.
- Transient protection: TVS, MOV, GDT and layout: sizing the clamp that the spike and surge rows call for.
- UN R10 (ECE R10): automotive EMC and the E-mark: the civil road vehicle EMC route.
- ISO 26262 automotive functional safety: civilian safety counterpart for vehicle electronics.
- AEC-Q100, Q101, Q200 automotive semiconductors: component-level qualification often paired with vehicle-bus immunity.
- IEC 62133 and UN 38.3 battery safety + transport: battery-pack design rules.
- DO-178C and DO-254 avionics: the aircraft side, where MIL-STD-704 applies instead.
Sources and references
Section titled “Sources and references”Sources & references
- MIL-STD-1275, Characteristics of 28 Volt DC Input Power to Utilization Equipment in Military Vehicles (ASSIST record, revisions A to F), US Department of Defense, DLA ASSIST quicksearch.dla.mil/qsDocDetails.aspx?ident_number=36186
- MIL-STD-1275F (AT), 7 September 2022 (full text downloaded from ASSIST, copy hosted by a third party), US Department of Defense cvgstrategy.com/wp-content/uploads/2023/04/MIL-std-1275F.pdf
- MIL-STD-1275E, 22 March 2013 (full text, everyspec mirror), US Department of Defense everyspec.com/MIL-STD/MIL-STD-1100-1299/MIL-STD-1275E_45886/
- MIL-STD-1275D, 29 August 2006 (full text, everyspec mirror), US Department of Defense everyspec.com/MIL-STD/MIL-STD-1100-1299/MIL-STD-1275D_5431/
- MIL-STD-461, Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment (ASSIST record, revisions C to H), US Department of Defense, DLA ASSIST quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35789
- MIL-STD-461G, 11 December 2015 (full text, everyspec mirror), US Department of Defense everyspec.com/MIL-STD/MIL-STD-0300-0499/MIL-STD-461G_53571/
- MIL-STD-704, Aircraft Electric Power Characteristics (ASSIST record, revisions to F Notice 4), US Department of Defense, DLA ASSIST quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35901
- MIL-STD-704F with Change 1, 5 December 2016 (full text, everyspec mirror), US Department of Defense everyspec.com/MIL-STD/MIL-STD-0700-0799/MIL-STD-704F_CHG-1_55461/
- ISO 7637-2:2011, Road vehicles, electrical disturbances from conduction and coupling, Part 2: electrical transient conduction along supply lines only, ISO www.iso.org/standard/50925.html
- ISO 16750-2:2023, Road vehicles, environmental conditions and testing for electrical and electronic equipment, Part 2: electrical loads, ISO www.iso.org/standard/76119.html
- DEF STAN 61-005 Part 6, 28 V DC electrical systems in military vehicles (reseller catalogue listing, secondary), UK Ministry of Defence (listing by Accuris) store.accuristech.com/standards/moduk-def-stan-61-005-part-6?product_id=2832294
Frequently asked questions
- What does MIL-STD-1275 cover?
- MIL-STD-1275F defines the operating voltage limits and transient voltage characteristics of the 28 VDC power at the input power terminals of utilization equipment connected to the power distribution system of military ground vehicles. Its foreword says it is neither a power source nor a power system standard: it covers the equipment, the conditions it must operate under and what it may emit back onto the bus. The vehicle design authority is responsible for delivering 28 VDC that meets it. Electromagnetic interference and electrostatic discharge are explicitly not covered.
- Which revision is current?
- MIL-STD-1275F, dated 7 September 2022, which supersedes MIL-STD-1275E of 22 March 2013. The DLA ASSIST record lists Revision A (17 September 1976, change notices 1980 and 1981), B (20 November 1997), C (23 June 2006), D (29 August 2006), E and F, and gives 6 September 2027 as the next review date. A contract still binds the supplier to the revision it cites.
- Is the 250 V event a spike or a surge?
- A spike. The standard defines a spike as an energy-limited transient of 1 ms or less and a surge as a transient longer than 1 ms. The injected spike test applies at least fifty 250 V spikes of each polarity at 1 second intervals, rise time 50 ns or less, ringing between 20 kHz and 500 kHz, single-spike energy up to 200 mJ. The surge is the 100 V, 50 ms load-dump-type event from a 500 mΩ source. In both cases the equipment must operate without degradation or damage, not merely survive.
- How low does the voltage go during engine start?
- To 12 VDC during the initial engagement surge, for at most 1 second, then to no less than 16 VDC during cranking, for at most 30 seconds, before returning above 20 V. Equipment that operates during starting must do so without degradation or damage. The 6 V figure often quoted comes from MIL-STD-1275D (2006), which allowed the initial engagement surge to fall to 6 VDC; revision E raised it to 12 VDC and F kept it.
- What does the reverse polarity test require?
- The equipment terminals are connected reversed to a 33 VDC supply for five minutes. Reverse current above the normal operating current of the equipment is a failure; afterwards the equipment is reconnected correctly and must operate as specified. Operation while reversed is not required.
- How does MIL-STD-1275 relate to MIL-STD-461?
- MIL-STD-1275F cites MIL-STD-461 for test mechanics only: the CS101 method to inject ripple, the MIL-STD-461 ground plane when the vehicle structure is the power return, and 461G appendix paragraphs for setup tolerances and spectrum analyser corrections. EMI compliance itself is outside its scope, and the equipment must show compliance with its EMI and ESD requirements before MIL-STD-1275 testing.
- Is MIL-STD-704 the aircraft equivalent?
- It plays the same role for aircraft: MIL-STD-704 sets the electric power characteristics at the input terminals of airborne utilization equipment, for 115 V AC, 270 VDC and 28 VDC systems. Its current revision is 704F (12 March 2004) with Change 1 (5 December 2016), revalidated on 24 June 2026. Unlike 1275, its scope excludes voltage spikes, and its 28 VDC normal steady-state range is 22.0 to 29.0 V, against 20 to 33 V in 1275F.
- What do I need on the bench?
- The test circuits in 1275F use power supplies holding plus or minus 1 % of the set voltage, line impedance stabilisation networks (one when the chassis is the return, two with a dedicated return wire), a spike generator that delivers 250 V ringing spikes (or an 8.2 microfarad source capacitor with the Figure 10 impedances), a surge circuit with two solid state switches and a 500 mΩ source, an ISO 7637-2 setup for emitted spikes, and an oscilloscope FFT or spectrum analyser for emitted ripple. Testing is at 23 °C plus or minus 5 °C.