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Everything about UPS.

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  • Everything about UPS.
    In the article, you will find information about UPS units that can be used in your home or business, both for local backup of a single device and for ensuring uninterrupted power throughout the building.
    The UPS market is constantly changing, not only in terms of new manufacturers, but also in terms of new UPS models and new technologies. If you find something interesting, it is worth describing it in this topic.

    The three basic types of power supplies are well known, but which one should you choose?

    Why do we use UPS?

    UPS (Uninterruptible Power Supply) allows you to maintain the power supply of the device when there is a power cut. The backup time is limited by the capacity of the UPS battery. You can use UPS to power devices that will disrupt your operation in the event of a power failure. For example, a laptop with a battery in the event of a power outage will continue to operate, but may lose its LAN or Wlan connection if the network devices lose power. UPS will reduce the impact of short power outages, if the outage is prolonged, save your work and shut down the systems safely. The UPS can also reduce the transmission of some disturbances from the utility grid. The tandem power generator + UPS will help reduce the impact of longer power outages, but this is a topic for a separate article.

    Offline UPS.

    When electricity runs out, the offline UPS starts the inverter (usually with an output transformer) and starts generating power for the connected equipment. The pause between the power failure and the start of operation is not zero, which may affect the receiver. Depending on the version, the UPS can generate an output voltage closer to a rectangle or a sine wave. Offline UPS can also protect loads against overvoltage by built-in elements (most often varistors) and to some extent filter network disturbances (filters based on inductance and capacitance). Offline UPS is mainly suitable for low-power devices, whose power supplies allow you to maintain continuous operation despite a momentary power outage.
    The advantage of the power supply is its low price and low energy losses (the UPS does not convert energy when the mains power is present). Offline UPS will work well when powering a small LAN or WAN node (router + switch), possibly a WLAN device, as well as a PC or a low-power server.

    UPS offline line-interactive.

    In addition to the features of a typical offline power supply, this UPS can stabilize the output voltage without switching to battery operation, and maintain synchronization with the input voltage phase. The UPS will allow to maintain the nominal mains voltage with fluctuations in the input voltage, when the input voltage window is exceeded, the UPS will enter the voltage generation mode. The scope of application similar to that in the case of offline, line-interactive UPS should be used where there are frequent periodic drops or excesses of the nominal mains voltage.

    UPS online.

    This type of UPS rectifies the input voltage and then re-generates the AC voltage (double conversion). UPS online starts working immediately. The output voltage is independent of the shape and frequency of the input voltage. The online UPS processes the input voltage all the time, which unfortunately causes losses. UPS recommended for all sensitive and critical IT equipment and power greater than a few kilowatts. An online UPS can supply hundreds of kilowatts, and it can also run in parallel with other units on a single rail to provide power in MW. The disadvantage of an online UPS is the higher cost of purchase, operation, as well as greater power loss when the input voltage is present.

    Buffer power supplies.

    With DC power, it is possible to use buffer power supplies. A buffer PSU is supplied with DC or AC voltage and produces a constant output voltage. The buffer power supply is characterized by low losses and immediate starting of operation during a power failure. It is mainly suitable for powering devices such as CCTV equipment, alarm control panels, etc.

    DC power systems.

    In some solutions, you may find devices powered with DC

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  • #2
    eDZio
    Level 16  
    Interesting article.
    I have several batteries with UPS, 100Ah. I would like to use them to build such an offline line-interactive UPS.
    Is it more profitable to buy a ready-made solution or build your own?
    The power that would be enough for me is up to 2kW. Although if the costs were to drop drastically, I could possibly fit in 1kW.
  • #3
    TechEkspert
    Editor
    Efficient 100Ah batteries can be used as an external battery pack for the UPS. It is not an easy task, as it is necessary to ensure safe use (e.g. to protect the circuits against short-circuit currents and to check whether the UPS charger will be able to charge the batteries within a reasonable time).
    The offline or online UPS used can be obtained from decommissioned or modernized IT infrastructure. You can choose a device with used batteries if other devices are to be used. The UPS will incorrectly indicate the backup time, for some models it is possible to calibrate it, but it is difficult to say whether it will be possible to perform it for a capacity of 100Ah.

    The project requires experience and caution due to the presence of mains voltages and high short-circuit currents.
  • #4
    eDZio
    Level 16  
    I have only one rectifier module from a 48V DC telecommunication power plant, efficiency about 50A. However, I have no idea how to run it, and whether it is possible at all, outside of this gym. Although it seems that the elements of which it is built could be used.
    I have no experience in building complex power systems. Taking this into account, I am wondering whether it is worth adapting a ready-made commercial device or building and gaining experience in this field.
    I did not pay a penny for the batteries and the rectifier, so I do not lose much.
  • #5
    TechEkspert
    Editor
    It is a difficult topic, errors in the design may result in serious consequences (fire, burns, electric shock).
    It is better to use the charger built into the UPS and check its possibilities (when it will charge the external battery).
    Generally, only the battery packs supplied / recommended by the manufacturer are recommended for UPS. The use of other kits is possible but requires experience and caution and is not recommended in a business application.
  • #6
    eDZio
    Level 16  
    While searching for ready solutions, I saw various UPS converters that could work with different batteries. Most often acidic or gel.

    As for the dangers, I am aware of them.
  • #7
    Frog_Qmak
    Level 25  
    The question is why, as a colleague mentioned, sometimes the positive power bus is earthed at low voltage circuits?
  • #8
    TechEkspert
    Editor
    Why is the positive bus grounded? I don't know, I'd love to know.
    Maybe it has to do with corrosion protection, or someone paid attention to the direction of the flow of electrons, or is it just such a standard?

    I wrote about this detail because the fact that the positive bus was grounded surprised me when I found such an installation for the first time. I was used to single and balanced power supplies where the reference point was 0V as grounded GND.

    Perhaps for someone who has been working in such gyms for years, this is the norm.

    However, the manufacturer took care of the good marking, I remember that there was a plate on the 48V side of the converter:
    "Rated output voltage of 48V DC with a grounded positive pole ,
    rated current 80A "
  • #9
    TechEkspert
    Editor
    Frog_Qmak wrote:
    The question is why, as a colleague mentioned, sometimes the positive power bus is earthed at low voltage circuits?


    We asked the Polish manufacturer of power systems for a positive power rail and received a very factual answer.

    The necessity to ground the positive (positive) pole of the 48V output voltage applies to power supply installations in telecommunications, this obligation results from the requirements of the PN-T-83102: 19996 standard - Power supply devices in telecommunications - DC telecommunications power plants, which states in point 2.3 that telecommunications power plants should have a rated output voltage of 48V with a positive earth pole.

    In power supplies for telecommunications, the fuses are in the negative (negative) circuit and therefore it is possible to ground the positive circuit.

    It is a mandatory condition only for 48V power systems in telecommunications, in other 48V power systems there is no such obligation.

    The grounding of the DC system other than the 48V telecommunications power plant can be done on a voluntary basis, but after making sure that there are no fuses or other protections in the grounded power path.

    Generally, in automation systems, the principle of grounding the minus pole of the output voltage is used (unlike in telecommunications).

    However, it is functional grounding used to increase immunity to electromagnetic interference. It is not a protective earthing in the sense of protection against electric shock.

    Information prepared in cooperation with the company Merawex .
  • #10
    Przemo1268
    Level 19  
    TechEkspert wrote:
    Efficient 100Ah batteries can be used as an external battery pack for the UPS. It is not an easy task, as it is necessary to ensure safe use (e.g. to protect the circuits against short-circuit currents and to check whether the UPS charger will be able to charge the batteries within a reasonable time).
    The offline or online UPS used can be obtained from decommissioned or modernized IT infrastructure. You can choose a device with used batteries if other devices are to be used. The UPS will incorrectly indicate the backup time, for some models it is possible to calibrate it, but it is difficult to say whether it will be possible to perform it for a capacity of 100Ah.

    The project requires experience and caution due to the presence of mains voltages and high short-circuit currents.


    You forgot one very important thing - most UPS, especially those that do not have the ability to connect external battery modules, are designed for a specific runtime in the backup mode. The use of batteries with a capacity greater than assumed by the manufacturer may overheat the internal circuits of the device (transformer, inverter transistors). Even these power supplies with an external battery module operate at their rated load for a certain period of time. Its elongation can also cause overheating. It all depends on the design of a given power supply, cooling method (active / passive) and the number of external battery modules with which the power supply can work.
  • #11
    TechEkspert
    Editor
    Any modifications to the devices carry risks in many areas. It's no secret that the devices are designed to meet the requirements with the minimum cost of materials. Therefore, when buying professional devices, they have strictly defined operating parameters and sets of matching extensions (e.g. external battery units).

    While working on anything, our scope remains to adapt all elements of the system to the new requirements ...

    In a business production system, the use of modifications is not recommended, but for personal use, why not.
  • #12
    alojzy7719
    Level 36  
    Hello
    I need a UPS to power my music equipment from an external soft-start power supply. The online topology UPS (for about PLN 1000) did not work (the equipment did not start, only the LED in the power supply from the above-mentioned equipment was flashing - probably due to the simulated sine wave). Will UPS Line Interactive AVR pass the exam?
  • #13
    CMS
    Administrator of HydePark
    What specific equipment do you want to power?
    A "real" sine wave in the case of musical equipment is an absolute must.

    Best regards.
    CMS
  • #14
    alojzy7719
    Level 36  
    CMS wrote:
    What specific equipment do you want to power?


    Mixing table. I care more about protection against overvoltage (the equipment is located in the countryside, where voltage drops are quite frequent) than using "battery" power.
  • #15
    CMS
    Administrator of HydePark
    How much reactive power do you need? And do you need a backup at all, because if the whole village is to run out of electricity, what will the equipment playing in complete darkness give you? Unless you have lighting for it. If so, as it is on light bulbs, I would rather suggest a generator, if on LED, ah, then the UPS will be enough for a few dozen minutes, but in the villages the breakdowns last longer. But this is already starting to get closer to OffTop. Coming back to the topic, if you do not need a battery backup, maybe instead of a UPS you should think about another, lighter and more adapted to your needs device. I suggest you think about an inverter with the possibility of connecting any battery and choose one that will be enough for the time of switching off and possible cooling (if it has fans) of the equipment.
    You will have filtration and protection against temporary voltage drops in the network.

    Best regards.
    CMS
  • #16
    alojzy7719
    Level 36  
    1100 - 1200W. I do not mean "playing" during a power outage, but I would like to connect the mentioned mixer (in order to protect it from surges, to which it is sensitive) and a computer to save the project and shut down the system. As I mentioned, the "online" UPS failed (in the case of the mixer), so maybe the "line-interactive AVR" will do.
  • #17
    CMS
    Administrator of HydePark
    Look for the APC Smart-UPS 2000VA-2200VA. They are available in stationary and rack versions.
    They are now on a well-known auction site, in a stationary version, for PLN 500 plus PLN 20 shipping. For this batteries, about 600-700 PLN and calibration - here prices vary depending on the service.

    Best regards.
    CMS
  • #20
    alojzy7719
    Level 36  
    About both?
    In that case, what is noteworthy, let's say up to PLN 700?
  • #21
    CMS
    Administrator of HydePark
    For that kind of money you won't get anything with the required power, with a "real" sine wave.


    Best regards.
    CMS
  • #22
    alojzy7719
    Level 36  
    Maybe a voltage stabilizer instead of a UPS? As I wrote, I care more about protection against surges.
  • #23
    CMS
    Administrator of HydePark
    Maybe you will be interested in something such . I mentioned such a solution earlier. Remember, however, that you still need a battery.

    Best regards.
    CMS
  • #24
    alojzy7719
    Level 36  
    Without exaggeration, I will not put a battery in the workshop that I would have to charge with a charger. It must be mains powered.
  • #25
    CMS
    Administrator of HydePark
    After all "it" is powered from the mains.
  • #26
    alojzy7719
    Level 36  
    Fact, I haven't read it. The question is how many Ah must the battery have and whether there can be two 12 volts connected in series. The second thing is the time to switch to "battery" supply in the event of a power outage.
  • #27
    CMS
    Administrator of HydePark
    12-18AH should be enough for you. You can connect two pieces in series (remember that then the capacity does not add up).

    Best regards.
    CMS
  • #28
    alojzy7719
    Level 36  
    That's right, just like with capacitors. Thanks for the suggestion, nevertheless I have concerns if it will work for sensitive (like a French doggy) electronics.
  • #29
    CMS
    Administrator of HydePark
    This device is used precisely to power sensitive electronics.

    alojzy7719 wrote:
    The second thing is the time to switch to "battery" power


    Negligible.
  • #30
    alojzy7719
    Level 36  
    Thanks, maybe I am looking for such a solution. In terms of batteries, I think it will be cheaper to buy two 12 volts.