What is UPS, how does it work, how many types are there, how much do they cost, which one does it for me? We will try to answer all these questions for you in this article, considering that we are addressing novice users.
What is UPS? UPS is the acronym for Uninterruptible Power Supply . It is a device that provides us with electricity just like a power outlet in our home, even if the electricity provider cuts off its connection to our home. In short, you have an outlet that will continue to supply power to your devices even if your electrical network goes out.
The capabilities of a UPS usually cover the uninterrupted supply of electricity for a few minutes. In other words, don't imagine that it will last an entire night or that you can go on vacation for a week and simply turn off the main electrical switch in your home. The time that UPSs offer is enough to safely turn off a sensitive electronic device and turn it back on when the power returns. Or until a generator starts up and provides you with power, that is, a diesel engine, which produces electricity as long as its tank is full of oil.
Do you need us?
Your home is full of sensitive devices. Your computer, your television, your stereo, and generally any electronic device is sensitive and requires a stable and continuous supply of electricity.
However, the entire electricity network in your home is not as stable as you think. If your provider offers you 230V- 50Hz and you decide to measure it with an instrument, you will see it constantly fluctuating from 190V to 250V. All of this depends on many factors and that is why each area has its own tolerance. Furthermore, when the electricity is cut off and then restored, at the moment of restoration you may even measure 500V.
Let's not talk about what happens to the network when there is a storm and lightning outside. Any devices plugged into the outlet can be destroyed in a split second and your provider may not compensate you, since the contract between you requires you to have installed a lightning protection device in your electrical panel (which no one does).
In short, the UPS is an essential device for limiting the effects of electrical incidents.
How UPSs work
UPSs are nothing more than a simple battery (or batteries) that, through a whole process and conversions, performs exactly as well as an electrical outlet in a house.
Its structure consists of the following main parts:
- The battery: A storage space for electrical energy.
- The Charger: A device that charges the battery.
- The Rectifier: Converts alternating current into direct current.
- The Inverter: Converts direct current into alternating current.
The third last components are usually an electronic board and it is not unfair to say that, at least for home UPSs, they consist of a battery, a board and the plastic parts. So, in small home UPSs, if the board breaks, you just throw it in the recycling bin.
The operating mechanism of each type of UPS is not the same, but they all follow the following general principles:
- When the utility grid is normal: The UPS battery is charged and ready for operation.
- When the power to the area is cut off: The direct current from the UPS battery is converted to alternating current and powers the electrical equipment connected to it.
How many types are there?
UPS are divided into three main categories that have to do with their technology and operation. Let's look at them:
A. Offline/Standby UPS
A UPS like this sits quietly in its corner, making sure its battery is always full and waiting for the power to go out. When it detects a voltage drop, it automatically switches the power from the mains to the battery. This change, and therefore the lack of power, takes from 20-100 milliseconds, which is not dangerous for most electronics.
Standby systems are the cheapest of their kind but have the disadvantage of having a delay in switching from mains to battery. If you have a UPS and it does not say what type it is, then assume it is Standby. They are not suitable for ultra-sensitive electronics, or even for normally sensitive but expensive electronics (servers etc.)
B. Line interactive
It is an Offline UPS (of case A) but additionally having an automatic transformer inside and has the following operating mechanism:
Under normal voltage conditions, the autotransformer will not affect the input voltage. The input and output voltage and power are exactly the same as that of the offline UPS and essentially what your provider provides you at any given time.
When the voltage of the power supply increases or decreases slightly compared to the preset standard limit, the automatic transformer will affect the input voltage so that the output voltage that powers your computer is kept at normal levels. Therefore, although your computer's power supply is still the local power grid, the input voltage and output voltage will be different.
Only in the event of a power outage will the unit eventually disconnect from the city grid circuit and switch to the battery circuit. The direct current from the battery is converted to alternating current.
It essentially has the same function as case A that we saw above, but it has a notable advantage over it, that it provides a network voltage stabilization function and that is why it is also more expensive. Especially if you have noticed the lights in your home flickering or dimming several times, then Line Interactive is ideal for you.
C. Online
In an online UPS (also called Double Conversion), your computer's electrical power is generated entirely by the UPS based on the following mechanism:
Under normal circumstances, the UPS will continuously convert the AC power from your utility to DC power with a voltage equal to the battery voltage, then convert that DC power back to AC power. It will then output this constant voltage.
When the power supply fails, the unit will use the battery circuit. The DC current from the battery is converted to AC current to supply power to your equipment.
Thanks to this function, the online UPS does not require even the minimum time to switch from mains to battery and thus ensures maximum stability in the output voltage. It is the most expensive category of its kind, but also the best.
UPS Features and Applications
The main job of UPS is to help electronic equipment avoid interruption, damage, or data loss due to sudden power outages. Depending on the purpose of use, and how much electrical power that equipment needs, the UPS can range in size from a simple power strip to a rack of cabinets.
Depending on the design, it can be compact (one box that contains everything), the batteries can be separate and the electronic part can be separate, or it can even be modular where additional batteries can be added at any time or replaced, without interrupting the power supply.
Also, depending on the power, they can be single-phase or three-phase. For your home, the usual case is single-phase. Finally, depending on the installation location, it can be a simple box, or it can be made to be placed in a 19” rack or it can be a tower type (tower, like desktop computers) or even a closet.
The most serious machines improve the quality of the power source, stabilize the frequency, offer noise filtering, protect against lightning, are equipped with reporting capabilities, and have the ability to gracefully shut down your computer before it runs out of battery.
Therefore, UPS is used extensively in the fields of IT, healthcare, industrial production, security and defense.
How much do they cost?
The range, as you can see from all of the above, is huge. There are very small UPSs on the market, up to huge cabinets. Their cost can range from 30.00 euros to several tens of thousands of euros. Usually a home UPS for a simple computer costs from 30.00 to 280.00 euros.
It depends on how good quality you want and how long you want to have autonomy. But what is autonomy?
Which one works for me.
This is a painful story. That is, knowing your power needs and by extension how big a UPS you need. Let's look at two basic technical terms.
UPSs are also measured in KVA (kilo-volt-amperes). This is a unit of electrical power, equivalent to the KW (kilo-watts) that your electrical appliances usually use.
KW is the actual power that a system uses usefully. However, every system also has losses. Thus, KVA is the total power consumption of a system (useful + losses). Hypothetically, we consider that losses are 10% of KVA and useful 90% of it. So to see how many KVA the UPS you want should have, add all the KW listed on the labels of the devices that you will connect to the UPS and then divide the total by 0.90. The result is the KVA you are looking for. The K in front of VA and W means va or watts multiplied by 1000.
So far so good, but with several assumptions. First of all, the labels refer to the maximum consumption of the machine, which will probably never reach this number. Especially in computers, consumption is measured by the KW of the power supply, which is usually much higher than the demand.
Let's skip this part for now and move on. UPSs usually, when they state how many KVA they have, calculate that if all these KVA are required then the machine will last about 5 minutes. If you want more, then the difficulties begin. Each UPS is accompanied by a performance curve or a table, where you can find how many minutes the UPS will last depending on how much load in Watts or KW you have connected to it.
You can find such tables on the manufacturer's website. For example, the APC BK500EI can power your devices for 3.9 minutes if they have a total consumption of 300 Watts or for 24 minutes if your devices have a consumption of 100 Watts.
So you can easily choose a machine as long as you know the Watt consumption and how much autonomy you want. For simple home situations with a desktop computer, an LED technology monitor and an inject printer, a 500 VA UPS will last you around 13 minutes and will cost you from 42.00 to 170 euros.
What about maintenance?
UPSs don't have as many requirements as your computer. They can withstand much higher temperatures and humidity. So, the computer will "hit" first and then the UPS. But be careful not to cover its ventilation holes and not to bathe it in coffee.
It has electrical protections and rarely burns out, but if you treat it roughly, it will give up on you. Pay attention to how many outlets it has, make sure they are enough for you, and check if the ones you are using are battery-powered and not simple mains sockets.
Finally, the battery(es) need replacing every 2-3 years. Replacing a home UPS is usually a simple matter. It requires a Phillips screwdriver and a little bit of dexterity.
Turn it off and unplug it, unscrew the battery cover and disconnect the battery from the two cables (red and black). Immediately press the power button to discharge the capacitors for safety reasons. Replace the battery, reconnect the cables in the correct position (the red one to the + pole of the battery), screw the cover on and you're done.
