How to choose an uninterruptible power supply (UPS) for a computer

The function of uninterruptible power supply (UPS, UPS - Uninterruptible power supply) for a computer is to provide for some time a continuous supply of electricity to your computer and peripheral devices in the event that the power supply for some reason has disappeared or the voltage in it has become much less than acceptable .

The problem does not apply to laptops, tablets, smartphones, because they have built-in batteries. But the computer does not have a built-in battery, so additional measures are needed.

This is necessary so that you do not lose unsaved information, being in an instant without electricity (the monitor went out sharply and that’s all), so that you have the elementary opportunity to shut down normally and turn off the computer in normal mode without unnecessary stress for you in a few minutes and without risks to the equipment.

How to choose an uninterruptible power supply for your computer? We will talk about this further. There are generally three most popular types. uninterruptible power supplies. Here they are:

• standby (offline, standby),

• line-interactive (line-interactive, smart-UPS),

• double conversion (online, double-conversion).

Redundant Uninterruptible Power Supply (Standby UPS, Offline UPS)

This is the most elementary type of uninterruptible power supply. It is easy to manufacture, inexpensive, consists of a basic set of parts: a battery, battery charger, DC-AC inverter. If a power failure occurs, power will be automatically supplied from the built-in 12 V battery with a capacity of 7 Ah or more. The duration of the backup operation depends on the capacity of the built-in battery.

The function of the charger is to keep the battery fully charged and ready for use at any time. At the time of switching to the reserve, the inverter will take 12 volts at constant current from the battery and convert them to 220 volts of alternating voltage to power the computer and peripherals. Switching from the mains to the inverter and vice versa takes place automatically, the electronics simply control the relay, and the switching time is measured here in units of milliseconds.

Such a UPS is suitable for a simple home computer, it is convenient to place it under the desktop or next to it. The rated power of Standby UPS is less than 1 kW.

Line-interactive UPS (line-interactive or Smart-UPS)

A smart or interactive uninterruptible power supply. It includes all blocks of an offline offline power supply, but it also contains a voltage stabilizer, with which it becomes possible to automatically equalize the voltage if it has fallen in the network, and without switching to battery power.

So, an uninterruptible power supply of the line-interactive type is able to work normally even when ordinary offline-uninterruptible power supplies would have switched to a battery. Thus, smart UPSs have a wider operating range of input voltages and more appropriate use of a backup battery. Due to the presence of a built-in stabilizer, the cost of “smart” UPSs, of course, exceeds the usual standby-models.

As a rule, smart UPSs have an active cooling system, which turns on only when necessary, and also differ in the ability to connect additional batteries.

Such UPSs switch faster, so you can even use them for backup power supply to servers and other equipment that is sensitive to the smallest power surges. Rated power is measured in units of kilowatts. These uninterruptible power units are conveniently mounted on racks together with rechargeable batteries.

Double conversion UPS (online, double-conversion)

Many people know that DC-AC inverters often work like that - they convert a constant low voltage of a 12 volt battery to a constant 310-340 volts, and then it is already converted to alternating voltage. So it is here. The input mains voltage is always converted to DC, which is then converted to AC at the output.

The simplest versions of double conversion uninterruptible power units have an efficiency of up to 90%, because a fraction of energy is lost on the conversion path. But there are models with active power factor correction (active PFC), in which the efficiency reaches 98%.

The advantage of a double conversion UPS is that it instantly switches to the battery and vice versa, there is no delay at all. This is important for equipment critically sensitive to quality supply voltage. In addition, the frequency at the output of such a UPS is always stable, and for the consumer, the power supply is not interrupted at all.

These uninterruptible power supplies provide the highest quality power supply. The rated power of a double conversion UPS is measured in kilowatts. The price is appropriate.

If the voltage in the network often jumps in your city or town, then a double conversion UPS is exactly what you need.

Individual power selection

UPS power is usually indicated in volt-amperes - this is the total power excluding power factor. For the sake of fidelity, it’s best to multiply this value by 0.75 to get the value in watts or kilowatts.

For example, if you chose a UPS that says “output power 800 VA” in the specifications, the operating time at full load is 5 minutes, which means that in fact the load should not exceed 550-600 W, and preferably 400 W (50% guaranteed rule ), then for 5 minutes you can safely count on - you will be able to normally finish working with applications and turn off the computer.

There are a couple of options to find out how powerful your computer is. The first is to read in the specifications for the monitor, motherboard, processor, video card, hard drive, etc. the values ​​of their maximum capacities and proceed from the sum of these data. And you can do it easier, especially when it comes to your home computer.

Take advantage power meter, connect the extension cord from the computer to the outlet through it, and in the course of your normal work, pay attention to the readings. Or count the readings on the counter: turn off all electrical appliances and leave only the computer to work. Use it for several hours, after noticing the counter. After the lapse of time, look at how much the meter wound and divide the wound by the number of hours. This will be the average power of your computer during working hours in kW.

Features of buying an uninterruptible power supply

Before buying a UPS, take an interest in a guarantee, at least a year of a guarantee is obligatory, but two years meet also. Ask the seller how far the service center is and whether it is in your city, what is the procedure for contacting the service center, if the need suddenly arises.

Is there control of the computer from the UPS via USB? It is important. There are UPSs that can send a signal to turn off the computer via USB when the voltage is gone. For such UPSs, the notification or response function according to the situation can be configured by the user. If you often leave the computer for a long time, then the USB control function for the computer with the UPS is for you.