Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [ups]

A UPS is an Uninterruptible Power Supply that provides backup power when the main power source is lost. Questions on repairing commercial ones are generally off topic.

A UPS typically has an AC to DC converter at the input, followed by a battery charger and batteries, and a DC to AC inverter at the output.

When the main AC power source is lost, power is provided to the attached device(s) via the batteries and inverter. When power is restored, the battery is recharged to be ready for the next power loss event.

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Some advice on charging circuit used in simple UPS

I have looked around for some way of having a 5 volt power supply that acts like a UPS. Basically want to use a micro usb connector for +5 have a battery and li-ion or other charging circuit that will maintain uninterrupted power on the output. I…
Piotr Kula
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12V DC UPS for Network Equipment

My requirement is to keep running supply of low power devices like DSL modems, etc. Most of these devices input 12V/9V DC so i don't see the value in using ordinary UPS which converts DC to AC then back to DC, lots of conversion lots of power loss…
Imran Naqvi
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Extending the backup runtime of a UPS with an external car battery

I'm looking for a simple/inexpensive way to have a longer power backup time. My fist thought was putting 2 cheap UPSes in parallel. But I quickly found it's not that simple. You would need another device that synchronizes the waves, otherwise...…
GetFree
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Don Lancaster's Magic Sinewaves

For several years now Don Lancaster is promoting magic sinewaves. They are strings of binary digits (like 420 bits for a full sine cycle) that, when used to drive a digital switch (MOSFET/IGBP), result in quite a clean sinewave (only very high…
jpc
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Does reactive power cause extra fuel use in a Diesel UPS?

It is a bit of a theoretical thing, of little practical use, but I just want to understand the physics behind it. I am aware that I'm simplifying things quite a bit. In electric power we differentiate Real, Reactive and Apparent power and of course…
jippie
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Can I connect a capacitor in parallels to power supply of a router

In the building where I live, because of older wiring, the mains voltage frequently drops for a fraction of a second and this restarts my wifi router. I am planning to solder a capacitor in parallel to either input or output of the 9V power…
Selcuk
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Battery Backup: C10 vs C20

I am installing a home UPS system of 1400 VA. The UPS is a 24 volt system and, based on the batteries available on the market for the UPS segment here, will need 2 x 12 volt batteries for it. Based on what the UPS service engineer told me, and my…
Sam
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5V ups circuit oscillating?

I'm trying to design a 5V UPS. Power to load should switch if line voltage falls below about 4V. Battery voltage may be from 3.8 to 5V. I'm simulating in LTSpiceIV. I'll be using mosfets to supply battery power to avoid schottky voltage drop.…
Indraneel
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DIY 12 Volt UPS

Hi i am trying to make a UPS for a project that requires 12Volts. I'm currently using a replay diode and capacitor. My problem is that when the switchover occurs, the voltage drops from 12Volts to 7Volts, and back up again. Does anyone have a…
littlebirdceo
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volt-ampere (VA) rating of UPS

I would like to ask about the volt-ampere (VA) rating of UPS. Is there any effect of this value in terms of the time period that the UPS can supply the power?
Adban
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Replacing a battery in a UPS

I recently replaced the battery in my APC Back-UPS CS 650 and of course I didn't opt for an original APC battery, but just bought a similar one from the corner electronics shop. Apart from the label both batteries looked exactly the same, but still…
jippie
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Two identical DC power supplies in parallel for redundancy?

I'm trying to design a power backup system for my saltwater aquarium. In short, the system will be powered by a 12VDC power supply while the mains power is on. On power failure, the system will automatically switch to a battery source until the…
user108567
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Why does a UPS need an isolation transformer?

Why would we need isolation transformers before and/or after for a UPS system? What are we trying to protect, and from what? I have read that it has to do with grounding and neutral but I didn't understand. This is 100KVA UPS. The inputs are 3…
Chebhou
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UPS vs portable power station capacity ratings

I have been looking to buy a dedicated 220V AC offline UPS or portable power station with an offline UPS functionality. What surprised me is that, whereas both are very similar devices, is that portable power stations are often rightfully so…
JJM Driessen
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Relay not switching immediately from switching power supply to battery backup

WARNING This project as currently described is badly flawed in a number of ways that are liable to lead to complete failure of the equipment. As it is stated that it is intended to be used in a life support system, equipment failures could result in…
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