Common DC voltage levels

DC voltage levels:

0.7V Nominal voltage drop on normal silicon diode or similar semiconductor junction

0.8V Voltages from 0V to 0.8V are considered to be logic 0 on TTL logic IC inputs

1.25V NiCd, NiMH battery cell nominal voltage

1.5V Carbon and alkaeline battery cell nominal voltage

1.6V The voltage you normally get from a fresh alkaeline battery cell

1.8V Quite commonly used very low voltage digital circuit operating voltage (many CPU cores)

2V Lead acid battery nominal cell voltage

2V Voltages from 2V to 5V are considered to be logic 1 in TTL logic IC inputs.

3V Lithium battery nominal voltage

3.3V LVTTL logic circuits operating voltage

3.6V Typical voltage used to power cell phones (either from NiMH or Li-Ion battery pack)

4.5V operating voltage for many small electronics gargets powered from three batteries

5V TTL logic circuits operating voltage

6V operating voltage for many small electronics gargets powered from four batteries

9V Commonly used battery voltage

10V Normal control voltage limit in 0-10V and 1-10V analogue control systems (light dimming and industrial use)

12V Car battery nominal voltage

13.8V the voltage you expect to get from car 12V power when car motor is running (charging battery)

24V Truck battery.
24V Automation systems most common nominal voltage used for logic signals and and current loop powering

24V common standard input voltages in Avionics and Defense applications

28V Maximum battery charging voltage for 24V battery system (for example batteries that power automation systems).

28V common standard input voltages in Avionics and Defense applications

36V Battery voltage used on some electric golf carts, electric scooters, electric bikes, high power cordless tools etc..

42.4V Voltages must be less than or equal to 42.4V peak/60V dc to meet safe limits and to be SELV.

42.4V Hazardous Voltage is a voltage exceeding 42.4V peak or 60V d.c., existing in a circuit which does not meet the requirements for either a Limited Current Circuit or a TNV Circuit.(IEC 60950)

48V Battery backed up -48V voltage is used on telecom systems for powering telephone exhanges and other telco equipment. The normal service voltage range for the -48 Vdc nominal supply at interface “A” shall be -40,5 Vdc to -57,0 Vdc according to ETSI EN 300 132-2

48V Some data centers use 48V DC to power servers (battery backup easy)

48V Phantom power feed for microphones in audio mixers most often uses +48V phantom power voltage
48V some automation systems use +48V power for equipment and I/O (electrical power distribution)

50V Work on energized circuits or apparatus below that voltage requires no “Hazard/Risk Evaluation.”     NFPA 7OE

60V Voltages must be less than or equal to 42.4V peak/60V dc to meet safe limits and to be SELV.

60V Hazardous Voltage is a voltage exceeding 42.4V peak or 60V d.c., existing in a circuit which does not meet the requirements for either a Limited Current Circuit or a TNV Circuit.(IEC 60950)

72V standard input voltage in rail applications

75V Low Voltage Directive is effective for voltages in range 50 – 1000 volts a.c. or between 75 and 1500 volts d.c

110V Seen on electrical power distribution control automation as IO voltage and for operating actuators on high voltage power distribution stations.

110V standard input voltage in rail applications

120V Extra-low voltage high limit is 120 V ripple-free d.c.

125V Commonly used insulation resistance testing voltage used for low voltage wiring testing where 250V test voltage is too much.

160V The highest DC voltage covered by the telephone/telecom/ITE industry is 160V (ANSI T1.311)

169V The peak voltage on 120V AC mains power is around 169V, you get around this voltage if you rectify and filter 120V mains power

220V Seen on electrical power distribution control automation as IO voltage and for operating actuators on high voltage power distribution stations.

250V Commonly used insulation resistance testing voltage. Tests on SELV and PELV circuits are carried out at 250 V.

270V common standard input voltages in Avionics and Defense applications

324V The peak voltage on 230V AC mains power is around 324V, you get around this voltage if you rectify and filter 230V mains power

380V DC power voltage for DC feed used on some data centers. Emerge Alliance pushes using this 380V system.

500V Commonly used insulation resistance testing voltage. Insulation tests at normal mains wiring (230V) is commonly tested with 500V test voltage. Minimum insulation resistance expected on mains circuit is 0.5 Mohm. Also test between SELV and PELV circuits and the live conductors of other circuits must be made at 500 V.

575V DC power voltage for DC feed used on some data centers

600V Voltage used on third rail powered locomotive systems and overhead lines for older trams

750V Voltage used to power trains in Helsinki subway (third rail powering) and also used in modern tram systems

1000V Commonly used insulation resistance testing voltage for circuits that operate above 500 V up to 1000 V.

1500V Low Voltage Directive is effective for voltages in range 50 – 1000 volts a.c. or between 75 and 1500 volts d.c

2500V Commonly used insulation resistance testing voltage

3250V Use 2300V rms or 3250V dc test voltage for dielectric-withstand test for double insulation

5000V Commonly used insulation resistance testing voltage when testing high voltage wiring


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  2. Danny Power says:

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  3. 24V Batteries Dekcell says:

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    [...]Common DC voltage levels « Tomi Engdahl’s ePanorama blog[...]…

  4. Teardown: Relay DIN rail base « Tomi Engdahl’s ePanorama blog says:

    [...] As you can see in the picture the whole product is designed for 48V DC operation. That 48V voltage level is used in telecommunications systems, on some data center applications and some a… [...]

  5. Tomi Engdahl says:

    Factory pre-configured with industry-standard voltages
    - ZSPM1511 output: 0.85 V
    - ZSPM1512 output: 1.0 V
    - ZSPM1513 output: 1.2 V

    “Many high performance field programmable gate array(FPGA), digital signal processor(DSP) and system-on-chip(SoC) applications require multiple supply voltages to power the FPGA, DSP, SoC, peripheral input/output devices and transceivers in the application,”


  6. Tomi Engdahl says:

    Power converters meet railway needs

    NAR150D DC/DC converters from Powerbox deliver 150 W of output power with typical efficiency of 93% for demanding railway applications. The dual-output units in the series are housed in slim 18.5-mm (0.73-in.) wide packages, allowing their use in tight, confined environments.

    Comprising a wide range of models, the ENAR150D series operates from inputs of 24 VDC (16.8 VDC to 30 VDC) or 110 VDC (77 VDC to 137.5 VDC) and provides two independent, isolated outputs of 12 VDC, 24 VDC, or 48 VDC.

    Able to meet the high-reliability requirements of the railway industry, the ENAR150D series achieves an MTBF of 500,000 hours at +45°C ambient. Converters provide a minimum technical lifetime of 15 years at +45°C and 80% load. Input-to-output isolation is 2100 VAC; output-to-case is 1000 VAC; and output-one-to-output-two is 500 VDC.

  7. Tomi Engdahl says:

    Home> Tools & Learning> Products> Product Brief
    Converters power automotive IoT designs

    ENA100 100-W and ENA200 200-W DC/DC converters from Powerbox are housed in IP21-rated plastic enclosures built for tough automotive applications

    The ENA100 and ENA200 series accept input voltages ranging from 10 V to 120 V (10 V to 18 V, 18 V to 32 V, 36 V to 75 V, and 55 V to 120 V). Output voltage choices include 12.5 V, 14.5 V, 24.5 V, and 28V.

  8. Tomi Engdahl says:

    AC/DC Power Supplies: Four Questions to Ask

    1. Can you connect the power supplies in parallel to provide higher output power or configure them to provide multi-phase or split phase outputs?

    2. What voltages and currents can I expect from modern power supplies?

    Voltage ranges have increased, particularly in military/avionics applications. Examples include:

    Standard avionics power plant simulation, which currently runs from 360 Hz to about 800 Hz.
    Simulation of next-generation avionics power plants already requires 1200 Hz and that will increase. Power at these frequencies is needed to test the electronics that will connected to those power plants.
    Torpedo alternator simulation, 3 kHz-4kHz, is needed to test the downstream power converters and electronics that will be connected to those alternators.

    Instead of the traditional 150 and 300 VAC ranges, the latest generation of AC/DC supplies now produce voltage ranges of 200 and 400 VAC, as well as DC voltages of 250 VDC and 500 VDC. These higher DC voltages come in handy in many applications. For example, MIL-STD-704, Test Method HDC302 requires voltage transients up to 475 VDC.

    3. I need to test my equipment at multiple ranges. What do I need?

    4. What features should I look for?
    Many of today’s AC/DC power sources have features that make testing easier and more effective. These include touchscreen displays dashboards and control panels where you can save your GPIB address or set your RS-232 parameters, or set up your LAN connection.

  9. Tomi Engdahl says:

    EN50155 Compliance to Railway Standards

    The specification is surprisingly relaxed compared to the typical industrial operating range requirements of -40°C to +85°C, as only the highest specification of TX rated parts need to cover this ambient temperature range for just 10 minutes during start up conditions.

    Conversely, the shock and vibration requirements are anything but benign, as one would expect in such a hostile environment as rolling stock. The requirements are detailed enough to warrant the calling up of a separate standard, EN 61373: Railway Applications – Rolling stock equipment

    The next section in the EN50155 standard covers the power supply requirements. The nominal input voltages are 24, 48, 72, 96 and 110VDC, of which 24, 48 and 110 are the most commonly used. Although not covered in the standard, 36V is also often requested.

    The standard defines the continuous input voltage range as being between 0.7 and 1.25 nominal, with short-term fluctuations between 0.6 and 1.4 being allowed. In practice, power supplies must work continuously between 0.6 and 1.4 nominal as no “deviation of function” is tolerated.

    A basic rule-of-thumb for DC/DC converter design is that a 4:1 input voltage range is the practical limit for most typical designs. Thus all of the nominal input voltages can be covered by just three standard converters

    An extreme example of the layered approach of EN50155 is the section in the standard regarding EMC, surges, ESD and transients. The standard covers these points in just two short sentences by referring to another standard called EN50121-3-2: Railway Applications – Electromagnetic compatibility Part 3-2: Rolling Stock – Apparatus.

    The last section of EN50155 sets out a useful checklist of all of the mandatory or optional type approval tests, along with a description of how to carry out the test or a reference to another standard which defines the test and pass/fail criteria.

  10. Tomi Engdahl says:

    The 5 Big EN50155 Compliance Requirements for Railway Applications

    Power Supply Input Voltage: EN50155 requires minimum voltages of 24, 48, 72, 96 and 110V DC. Power supplies utilized for railway applications must operate within 0.6 and 1.4 nominal with no deviation. This is to ensure that every railcar can functionally operate. It is also advantageous to implement an input capacitor, which will help to level out any ripple voltage, creating more DC input consistency.

  11. Tomi Engdahl says:

    The Next Opportunity for Utility PV Cost Reductions: 1,500 Volts DC

    The average cost for a 20-megawatt fixed-tilt utility PV project in the U.S. in 2015 is just above $1.50 per watt — relatively cheap in historical terms. However, with record-low PPAs being signed at these levels, even subtle changes in component costs can kill projects.

    The most immediate opportunity that we see for utility-scale PV system cost reduction is the installation of 1,500 Vdc systems. Higher-voltage systems enable longer strings, which allow for fewer combiner boxes, less wiring and trenching, and therefore less labor. According to our research, installing 1,500 Vdc systems in place of now-standard 1,000 Vdc can lower costs by as much as $0.05 per watt.

    Déjà vu: The history of higher-voltage PV

    If this conversation seems familiar, it’s because we’ve had it before. Prior to 2013, most systems in the United States were installed at 600 Vdc, while systems in Europe were installed at 1,000 Vdc. This enabled lower system costs in Europe, while installers in the U.S. were kept at low voltages by UL testing limitations and the National Electric Code, which limited voltage to 600 Vdc due to a broadly interpreted revision added in 1999.

    In 2013, however, many authorities began allowing 1,000 Vdc systems for commercial and projects, and UL standards evolved to enable this.

    From an installation perspective, the shift to 1,500 Vdc has similar benefits and regulatory barriers to the 1,000 Vdc transition.

    The beginnings of 1,500 Vdc

    When 1,000 Vdc systems became prevalent in the United States, there was already widespread availability of products from Europe, and thus the testing standards were the main barrier. Testing standards are also a barrier to 1,500 Vdc, but 1,000 Vdc is still the standard voltage in Europe, and so there is also exceptionally limited availability of 1,500 Vdc products.

    This doesn’t mean Europe didn’t lead the U.S. again with 1,500 Vdc. Europe’s electrical standards body, the International Electrotechnical Commission (IEC), considers 1,500 Vdc the low-voltage limit and enables certification to that voltage.

    As a result of these industry efforts, 1,500 Vdc parts are now commercially available for every system component. But module manufacturers are limited by the existing standards landscape.

    Product availability has been the primary barrier to 1,500 Vdc in Europe, but product introductions have been hampered by standards in the United States. Nobody wants to introduce a product that is unable to be used in the U.S. market. UL 1703, the gold standard for PV modules, currently only enables module testing to 1,000 Vdc.

    We expect all standards issues for 1,500 Vdc to be resolved in the next two years.

    As these regulatory barriers dissolve, manufacturers will begin to introduce 1,500 Vdc products in volume. We expect this to begin in mid-2015 and continue into 2016.

    1500 VDC Collection Systems

  12. Tomi Engdahl says:

    1,500 Vdc Utilization Voltages in Ground-Mount Applications

    EPCs in Europe pioneered 1,500 V plant architectures, just as they were first to market with 1,000 V PV systems. Belectric, for example, is an international solar project developer headquartered in Germany, with a long history of innovation and market firsts such as the construction of the first thin-film PV system in Europe (2001). According to a company press release, in June 2012 Belectric constructed and commissioned the world’s first utility-interactive 1,500 Vdc solar power plant. Power Conversion, a Berlin-based division of GE Energy, supplied the liquid-cooled inverters used to connect the 1,500 Vdc system to the utility grid.

    In conjunction with GE Power Conversion, First Solar began publicly touting the benefits of 1,500 Vdc solar arrays in early 2014.

    When you consider the broader development and deployment of 1,500 Vdc systems, the rest of the utility-scale solar industry is not far behind First Solar’s lead. At the risk of oversimplification, 2015 was most notable for the widespread release of 1,500 Vdc–rated components—modules, inverters, combiners, fuses and so forth—certified to UL standards. In 2016, a second wave of large-scale project developers, including Recurrent Energy, began selectively deploying 1,500 Vdc PV systems as a way of testing the waters and building a knowledge base for the widespread adoption of 1,500 Vdc systems in 2017.

    According to 1,500-Volt PV Systems and Components 2016–2020 (see Resources), a GTM Research report, 1,500 Vdc systems will account for 4.6 GW of global utility-scale solar installations in 2016. Though GTM Research analysts estimate that the US market will account for roughly 60% of the 1,500 Vdc field deployments worldwide in 2016, they expect that demand in the rest of the world will dwarf that in North America from 2017 forward. In other words, once early adopters have proven the technology benefits in the field, analysts expect to see a steady transition from 1,000 Vdc to 1,500 Vdc.

  13. Tomi Engdahl says:

    Getting ready for a lower-power future: the keys to successful adoption of new low-voltage memory ICs

    Today, the circuitry on the board in mainstream industrial and consumer products operates from a wide range of supply voltages: the power rails are most commonly at 5V, 3V, 2.5V, 1.8V and various lower voltages. To ensure compatibility between devices from different manufacturers, and to avoid unnecessarily complicating board-level power system design, merchant semiconductor manufacturers typically design their standard products to run from one or more of these standard power rails. But there is a strong force resisting this general preference for stability and compatibility. It can be summed up in one word: mobility.

    So every milliwatt saved from the power budget is important to product designers. And for them, the industry’s use of power rails at various standard voltages, often at 1.8V or higher, is a problem, not an advantage: that is because many components – particularly those operating in the digital domain – would with some modification be quite capable of operating from a power rail at a voltage lower than 1.8V, resulting in valuable savings in active and stand-by power consumption.

    Clear direction of travel
    Today, system designers typically have to provide multiple power rails in order to accommodate components operating from different supply voltages. Analogue devices such as sensors commonly have a 3V or — in industrial applications — even a 5V supply. Legacy digital components might have a 3.3V, 2.5V or 1.8V supply. At the low end of the voltage range, the latest applications processors or systems-on-chip built on advanced process nodes, such as 28nm or smaller, might have a core operating voltage as low as 1.0V.

    Figure 1 shows how DRAM technologies have led the memory IC industry beyond 1.8V. Standard DDR2 DRAM was the last to use a 1.8V supply. After that, successive generations of DDR DRAM operated at 1.5V (DDR3), then 1.37V (DDR3L) before reaching today’s level, 1.2V (DDR4).

    Figure 1 also shows in green the supply requirements of successive families of NOR Flash ICs from Winbond, operating at the standard 3V, 2.5V and 1.8V levels. Now the latest NOR Flash families offer two voltage ranges: one at 1.2V, and another with an extended voltage range nominally at 1.5V.

    In supporting the 1.2V voltage and the extended 1.5V level with its newest generation of NOR Flash ICs, Winbond is seeking to harmonise its product offerings with the broader semiconductor industry.

    Feature set compatible with 1.8V devices
    Winbond has designed the new 1.2V series and extended 1.5V series to match the existing 1.8V devices.

    Momentum behind 1.2V and extended 1.5V power rails
    Winbond has decided to be first to market in the serial Flash sector with 1.2V and extended 1.5V devices to give early momentum to a trend that seems certain to gain speed as manufacturers of battery-powered devices look for further savings in power consumption.

    These 1.2V products have been designed in and endorsed by new chipset companies working in the low power area like Espressif

    As a result, the Flash market is ready to standardise on 1.2V and extended 1.5V as the next power node below 1.8V,

  14. Tomi Engdahl says:

    What’s Ahead for the Venerable 12-V Automotive Battery?

    To improve fuel efficiency, 48-V systems are supplementing 12-V batteries, especially in the emerging world of mild hybrids.

    Many pundits believe that given the greater proliferation of more electronics in modern automobiles with each new model year, the decades-old, sealed lead-acid (SLA) 12-V car battery is being strapped to handle automotive power demands. Not only are more infotainment and safety electronic features being added every year, but when you include stricture emission and fuel-economy requirements, one can surmise that even the most efficient SLA battery in use today needs some help.

    That said, the 12-V battery is here to stay, at least for the near term—i.e., the next few years. But it has its many drawbacks, including the fact that the lead element is hardly in vogue ecologically. And except for a few applications that need its heavy weight, the heavier higher-voltage batteries like 24 V or 36 V just weigh down the car further.

    That said, the 12-V battery is here to stay, at least for the near term—i.e., the next few years.

    And except for a few applications that need its heavy weight, the heavier higher-voltage batteries like 24 V or 36 V just weigh down the car further.

    In fact, a 42-V auto battery system was proposed in the late 1990s in favor of 48 V to supplement the 12-V battery for automotive electrical power. The 48-V approach was deemed optimal in terms of fuel-efficiency savings, helping auto manufacturers meet emissions standards, and providing more power for the growing number of features desired by drivers to propel electric motors and electronic systems.

    The 48-V supplement to a 12-V battery has been demonstrated to be a better approach by Controlled Power Technologies

    In 2011, several German auto manufacturers introduced cars with on-board 48-V systems known as mild hybrids. This mild 48-V electrical system is emerging as the next revolution in cars.

    At a weight of 8 kg (17.6 lbs), the mild hybrid is not much heavier than existing 12-V batteries, and it is comparatively smaller

    The demand for mild-hybrid Li-ion 48-V batteries is rapidly growing, particularly in Europe and Asia, according to an IHS study. Automotive experts believe that by 2025, one fifth of all cars sold around the worldwide will have some sort of 48-V technology for power.

  15. Tomi Engdahl says:


    48 Battery, Telecom, Automation, Data Centers, Microphones
    60 Hazardous voltage (42.4V Peak or 60V DC) (UL, IEC, CSA)
    72 Rail
    110 Power Distribution Control, Rail
    160 Highest DC Voltage Covered by Telephone/Telecom/ITE Industry
    170 Rectified 120V AC Mains
    220 Power Distribution Control
    270 Avionics, Defense
    340 Rectified 240V AC Mains
    96-375 Electric Vehicles
    380-575 Telecom, Data Centers
    200-600 Grid Tie Solar
    680 Rectified 480V AC Mains

  16. Tomi Engdahl says:

    Voltage Values

    In the following, “voltage” means the voltage between the conductors. The standard voltage values used are:

    1. Extra low voltage (ELV) – means any voltage not exceeding 50V a.c. or 120V ripple free d.c.
    2. Low voltage – means any voltage exceeding 50V a.c. or 120V ripple free d.c. but not exceeding 1kV a.c. or 1.5kV d.c.
    3. High voltage (HV) – means and voltage exceeding 1kV a.c. or 1.5kV d.c.
    4. Extra high voltage (EHV) means any voltage exceeding 220kV.

  17. Tomi Engdahl says:

    +270 VDC input per Mil-Std 704F

  18. Tomi Engdahl says:


    DC normal operation characteristics

    28 Volt DC system
    22.0 to 29.0 Volts

    270 Volt DC system
    250.0 to 280.0 Volts

  19. Tomi Engdahl says:

    Coaxial power connector

    A coaxial power connector is an electrical power connector used for attaching extra-low voltage devices such as consumer electronics to external electricity. Also known as barrel connectors, concentric barrel connectors or tip connectors, these small cylindrical connectors come in an enormous variety of sizes.

    There are many different sizes of coaxial power connectors

    Contact ratings commonly vary from unspecified up to 5 amperes (11 amperes for special high-power versions). Voltage is often unspecified, but may be up to 48V with 12V typical.

    The sizes and shapes of connectors do not consistently correspond to the same power specifications across manufacturers and models.

    Generic plugs are often described by their inside diameter, such as 2.1mm DC plugs and 2.5mm DC (direct current) plugs. 5.5mm OD plugs

    next-most common size is 3.5mm OD with a 1.3mm ID

    There are several standards in existence, such as IEC, EIAJ in Japan and DIN in Germany.

  20. Tomi Engdahl says:

    High-Voltage Vehicle Systems Are Here To Stay


    As electrification takes over automotive design, efficiency becomes crucial, which has reignited interest in the dual-system approach using

    12 V and 48 V.

    The auto industry is rapidly moving toward what might be called “total vehicle electrification,” in which everything that can be powered by

    electricity rather than hydraulics or belts will undergo that transformation. Very simply, engine-driven components powered by electricity

    reduce the load on the engine, fuel consumption, and thus emissions.

    In addition, the increasing number of electronic systems, such as ADAS, employed in vehicles creates higher demand for power. As a result,

    the auto industry intends to supplement current 12-V power with a separate 48-V system, each one dedicated to specific needs.

  21. Tomi Engdahl says:

    The Thin Line Between Safety and Death on the London Underground | The Tube | Spark

    Third-rail current collectors

  22. Alan Muller says:

    I would add 32 volts which was/is a common marine voltage and also used for freestanding rural electric systems. 32 volt systems are no longer common but not entirely extinct.

  23. Tomi Engdahl says:

    12 vs 24 Volt Solar Systems

    Which voltage should you choose for your house? Here’s what you need to consider when choosing between 12 and 24 volt systems.

  24. Tomi Engdahl says:

    EEVblog #1015 – Beware Evil (But Clever) DC Jacks!

    Trivia time. Dave explains one of the reasons why annoying centre negative DC power jacks exist.


    Nice video. I always thought it was a Japanese thing.

    I’m scratching my head at why the pass through being on the sleeve is a reason for making the sleeve positive. It works just as well negative. I do it all the time, battery negative on the pass through, disconnects battery when plug is inserted just the same.

    Either way one end of the battery is floating, so who cares where exactly it’s floating.

  25. Tomi Engdahl says:

    750-V DC Input Railway Converter Delivers High Conversion Efficiency
    ABSOPULSE’s HVI 41R-F1 converter incorporates an input surge withstand capacity of 1300 V dc.

    The HVI 41R-F1 converter operates from 750 V dc (525 V to 975 V dc), the traction voltage required for mass transit vehicles including trams, metros and light rail, mining locomotives, and trolleybuses. It also incorporates an input surge withstand capacity of 1300 V dc. The unit delivers a regulated output of 24 V dc/2 A.

    The converter is designed for an operating life of up to 30 years. The elimination of optocouplers from the feedback loop contributes to significantly lower component count and higher MTBF compared with conventional designs, according to ABSOPULSE. The design is verified for 5600-V dc input-to-output isolation. Production level testing is 5000-V dc input-to-output. Other electronic protection includes inrush current limiting, reverse-polarity protection, and output current limiting with short-circuit protection.

    The HVI 41R-F1 meets the requirements of EN 50155 for electronic equipment used on rolling stock, including EN 61000-4-2, EN 61000-4-3, EN 61000-4-4, and EN 61000-4-6 standards. Heavy filtering on the input and output ensures compliance with EN 50121-3-2.

    The 50-W converter is cooled by conduction via baseplate.

  26. Tomi Engdahl says:

    International Standard IEC 60038:1983 defines a set of standard voltages for use in low voltage and high voltage AC electricity supply systems.
    According to it anything anone 1000V AC and 1500V DC is high voltage.
    Extra low voltage is below 50V AC and 120V DC.

  27. Tomi Engdahl says:

    Telecom sites typically have a battery backed up -48 VDC Power Supply in them. It was originally designed to power PSTN central office equipment, and since used to power very many other telecom and networking equipment.

    Battery backed up is also used with telecontrol RTUs:
    Sure, you might have commercial AC available at a remote site, but what happens during an outage?

    That’s the moment when your protected DC power plant (commonly -48, +24, or +12 VDC) comes into its own. If your RTU is powered by that DC power source (ideally a redundant power input setup, with one input fed by the rectifier and another by the battery string), it will continue to operate during the times when you need it the most.

  28. Tomi Engdahl says:

    Wide variety of input versions are suitable for 12V and 24V automotive vehicles, 48V, 72V and 96V industrial vehicles as well as 28V defense, avionics and marine systems, not forgetting most railway systems from 24V up to 110V.


  29. Tomi Engdahl says:

    Why does the aerospace industry use a 28V DC power supply?

    What you are observing is not really a physical difference, it’s just different conventions for defining the system. The aircraft in question do use 24-volt batteries. They use 28-volt generators, though. We want the generator to produce excess voltage that can be used to keep the battery charged. Similarly, for a 12-volt battery, a 14-volt generator would be typical.

    Aviation tends to define the system based on generator voltage while other industries, such as automotive, tend to define the system based on battery voltage. Your 12-volt car battery is probably connected to an alternator putting out 14-volts.

    As for why 28-volt instead of 14-volt – there are a few reasons. One is that higher voltage means smaller wires can be used, saving weight and thus fuel. Another is that during early days, someone came up with a really good and light 28-volt generator that worked well with other aviation equipment and it became common and then a standard,

  30. Tomi Engdahl says:

    Lucid said it is able to hit this benchmark because the vehicle has a 900-volt electrical architecture when combined with its lithium-ion cells, battery and thermal management system and powertrain efficiency. Most electric vehicles — with the exception of the Porsche Taycan and future Kia EVs — have a 400-volt architecture.


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