What is a UPS? (Uninterruptible Power Supply)

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An Uninterruptible Power Supply is a device that is used to keep computers and equipment safe when there is a loss, or a significant reduction, in the primary power source.

Once this is detected, the control is transfer over to the batteries, and via an inverter, the batteries DC voltage is converted into AC for the devices.

In reality, it doesn’t have to be computers systems and equipment that are kept alive by UPS. It could be anything from a fish tank, to a foot massager!

We aren’t just talking about plain power outages, lights off, TV off, everything, but we can sometimes get spikes in power where a sudden drop can assure our devices are momentarily powered off, or something known as a brown-out.

The amount of time the UPS can sustain a system for can vary, but it allows the opportunity for the issue to be resolved, or at the very least, allows for the systems to be shut down in a controlled manner.

Since a UPS is a system that uses batteries to power a system should the supply be compromised, we, of course, have batteries and a battery charger.

Since the batteries use DC current and our incoming supply is AC current, we need to convert DC to AC using an inverter.

A UPS provides second-level surge protection, but although it does provide some protection, it should usually be used alongside an adequate Surge Protection Device (SPD) to extend the life of the UPS as well as the attached equipment.

Firstly, and the most common in smaller systems is the Standby or Offline UPS.

The Standby UPS lays in wait for its time to spring into action, and once there is a power failure, it takes control. The Standby UPS tends to be the most cost-effective UPS available.

Next up, we have the Line Interactive UPS. It is very similar to a Standby UPS but with the added ability to regulate voltage automatically.

This means that it monitors the incoming supply and can help out if it detects that the voltage is a bit low, or a spike is causing it to go too high.

It can add or subtract power in this way to make the output to our devices constant!

This type of UPS is particularly useful for the brown-out situation we’ve already mentioned, or power spikes or surges.

Now we have the Online Double Conversion UPS. This type of UPS is efficient as the primary source of power isn’t the incoming supply, rather it is the battery power.

So when we have a power outage, there is no transfer switch to close, meaning no time to switch that you can get with the other type of UPSs.

When the incoming supply is ON, the batteries simply charge up. It is called a double-conversion because it converts the AC incoming supply to DC, and then the inverter converts it back to AC for the output.

In general, it ensures a far higher degree of isolation of the load from the irregularities on the mains supply.

These are the most common types of UPS available. Of course, there are other types that fit a particular form or function, but these tend to be for more specialist needs.


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  1. ARPIT Mishra on February 26, 2021 at 10:01 pm

    very good explanation

  2. hussain6953 on February 26, 2021 at 10:02 pm

    Great Job.

  3. Frs Kwn on February 26, 2021 at 10:03 pm

    What if I plug in something that requires more wattage into my UPS’ "battery and surge protection" sockets for the sake of not having "Surge only" sockets . Would it damage my equipment?

  4. huynh tuanphuong on February 26, 2021 at 10:04 pm


  5. Omen Dragon on February 26, 2021 at 10:06 pm

    Just found out this existed. Good to know.

  6. Sudeep Biswas on February 26, 2021 at 10:06 pm

    Nice sir !!!

  7. Lebone Ledwaba on February 26, 2021 at 10:07 pm

    Very informative video, thank you very much 👍

  8. suriya prakash on February 26, 2021 at 10:09 pm

    Can you put a video on Gas flow meters like RPD meter, Turbine meter, Ultrasonic meter and its uses and selection based on application.

  9. Rob erto on February 26, 2021 at 10:14 pm

    Hello: thanks a lot for your video. Could you please inform if this video is for commercial UPS’s and not for Industrial UPS’s? Regards.

  10. Waseem Haider on February 26, 2021 at 10:17 pm

    Can you please explain Static switch in UPS. Its construction,its components and its working.

  11. ahmed adardor on February 26, 2021 at 10:17 pm

    Thanks all realpars team

  12. samhoodnificent on February 26, 2021 at 10:18 pm

    Is it possible to run the UPS on a solar system for off the grid power for a house

  13. Furaido Chikin on February 26, 2021 at 10:18 pm

    I will buy ups now

    Thanks for the info

  14. coltz89 on February 26, 2021 at 10:18 pm

    Do your courses cover FBD and STL as well? I notice a lot of the icons are ladder which isn’t used in my company. Thanks!

  15. Celso Madeira on February 26, 2021 at 10:19 pm

    Excelente! Good job! Real pars each time better

  16. random stuff on February 26, 2021 at 10:20 pm

    3:48 why separate the battery charger and the rectifier? Battery chargers already have rectifiers in them.

  17. Alex አመክንዮ on February 26, 2021 at 10:20 pm

    Can i use an ips ( Instant power supply) instead of an ups?

  18. Zdan Germany Zydan on February 26, 2021 at 10:21 pm

    Excuse me,what is defference between UPS online and offline?

  19. Mark Allen on February 26, 2021 at 10:21 pm

    Wow, I bet those UPSs drain out pretty good when the wind ain’t blowing. Even with the wind blowing you’d only have a very small percentage of what you really need to make things work. Due to this, I doubt the accuracy of your entire video. I’ll stick with my APCs and Salem nuclear plant, thank you.

  20. ramin alikhani on February 26, 2021 at 10:22 pm

    Excellent! I barely could finish high school but I could understand everything in this video, because the explanation was brilliant! Now I can send my resume as an electronic engineer!

  21. Anirban Jana on February 26, 2021 at 10:24 pm

    When the electricity is available, does the UPS charge automatically?? Or should we need to switch off the UPS and charge it???

  22. Jiwan Verma on February 26, 2021 at 10:25 pm

    Pls inform do we need to keep ups switch on from switch board( switch off from powwer button) all the time even when we are not working on computer. Keeping switch on all the time affects internal part as ups get little hot. UPS ( APC BACK 600 IN).

  23. Chris Brand on February 26, 2021 at 10:25 pm

    Thank you very much

  24. safa haidar on February 26, 2021 at 10:26 pm

    is the battery charger coming with rectifier in online and offline ups just like the double conversion ups?is there any battery charger in double conversion ups? please clarify it for me

  25. Xenia Kekae on February 26, 2021 at 10:27 pm

    I’m a business student working with a Tech Company now and this video was perfectly explained. GREAT JOB!

  26. Riyadh H on February 26, 2021 at 10:27 pm

    Great explanation! 👍

  27. Fred Dukes on February 26, 2021 at 10:28 pm

    Confused on how much wattage of the UPS I should buy, I have a high end gaming rig and here are my specs.

    CPU: ryzen 5 3600
    RAM: T-force delta 2×8 16gb ddr4 3000mhz
    GPU: RTX 2060 SUPER 8gb

    Do I need a UPS with a wattage higher than my PSU? Any advice would be appreciated!

  28. Derin A. Maleek on February 26, 2021 at 10:33 pm

    hello ….please make a video about (SPPA T 3000) CONTROL system best regards

  29. kapil6996 on February 26, 2021 at 10:35 pm

    Nice video Sir. Please make video on SPD, Barriers and Isolators. Difference between barrier and isolator

  30. Nikki Holbert on February 26, 2021 at 10:35 pm

    So..if I’m building a pc..Do you buy this instead of a power supply or do you get both?

  31. Sheraz Saeed on February 26, 2021 at 10:35 pm

    you r one of the best technical youtuber by far distance😍

  32. Sagar sawant on February 26, 2021 at 10:36 pm


  33. RealZanzi on February 26, 2021 at 10:37 pm


  34. Wail Rimouche on February 26, 2021 at 10:39 pm

    Can we get a variable frequency drive that is also a UPS?

  35. Liou Jason on February 26, 2021 at 10:39 pm

    This video is very helpful.
    deeply thankful.

  36. Alikhan Zulkashov on February 26, 2021 at 10:42 pm

    I would like to ask if the battery charger works as the same as the rectifier does converting AC to DC?

  37. BR Electricity KH [បូរី] on February 26, 2021 at 10:43 pm

    Thank you very much bro for sharing video ups good.

  38. Eliel Murmu on February 26, 2021 at 10:44 pm

    Very helpful!

  39. Gangsta A Glide on February 26, 2021 at 10:46 pm

    Thaaank youu sir

  40. Hassan Faheem on February 26, 2021 at 10:46 pm

    Please Do make a video on wapda inverter and conveter

  41. Kenny W on February 26, 2021 at 10:47 pm

    Great channel and great content.

  42. khushi jain on February 26, 2021 at 10:48 pm

    Thankful to you that we can learn!

  43. Arumuga Raja Palraj on February 26, 2021 at 10:49 pm

    Nice video 👌 ( UPS )
    Please upload how to transfer the load to battery bank ( Setting ) & troubleshooting

  44. Nik97LL on February 26, 2021 at 10:50 pm

    you made me fulfill some gaps i had in Marine Electric Propulsion systems (in rectifiers and invertes) THANK YOU!!!

  45. Ibrahim Daruwala on February 26, 2021 at 10:52 pm


  46. Amira Janah on February 26, 2021 at 10:53 pm

    Thank you for the video , the explanation was so brilliant, now how can i size the UPS power of a system ?

  47. rose e on February 26, 2021 at 10:54 pm

    thank you for this :))

  48. ramin alikhani on February 26, 2021 at 10:54 pm

    Much better than wikipedia!

  49. Engineer SAM on February 26, 2021 at 10:57 pm

    Can we know which type of UPS are we dealing with by looking at its brochure?

  50. Loyiso Vamsinya on February 26, 2021 at 10:58 pm

    Good work keep it up wish u guyz can create more stronger ups the one can manage heavy load for example fridge that will be better

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