Max. output power
The maximum output power supplied by the UPS, in other words, the highest apparent load power allowed for this model.
This indicator is measured in volt-amperes (the general meaning of this unit is the same as that of the watt, and different names are used to separate different types of power). The total power consumption of the load, implied in this case, is the sum of two powers — active and reactive. Active power is actually effective power (it is indicated in watts in the characteristics of electrical appliances). Reactive power is the power wasted by coils and capacitors in AC devices; with numerous coils and/or capacitors, this power can be a fairly significant part of the total energy consumption. Note that for simple tasks, you can use data on effective power (it is often given for UPS — see below); but for accurate electrical calculations it is worth using the full one.
The simplest selection rule for this indicator is: the maximum output power of the UPS in volt-amperes should be at least 1.7 times higher than the total load power in watts. There are also more detailed calculation formulas that take into account the characteristics of different types of load; they can be found in special sources. As for specific values, the most modest modern UPSs give out
700 – 1000 VA, or even
less — this is enough to power a PC of average performance; and in the most "heavyweight" models, th
...is figure can be 8 – 10 kVA and higher.Charging USB A ports
The number
of USB A connectors provided in the UPS, designed to charge external devices, such as smartphones or tablets.
This number corresponds to the number of gadgets that can be simultaneously charged. True, it is worth considering that not every UPS with this function is able to charge USB devices from its own battery, without external power supply - it is better to check this possibility before buying.
DC output
The presence of
a DC connector (or several such outputs) in the device for powering external devices with direct current. A standard DC jack is round in shape and has a pin in the center. However, its dimensions may differ in depth and diameter. The voltages output to the DC output may vary.
Protection
The protection functions provided in the design of the UPS.
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Short circuit protection. A short circuit is a sharp drop in load resistance to critically low values, due to which the current strength increases and the UPS experiences significant overloads that can disable the device and even cause a fire. It may be caused by a problem with the connected device, poor insulation, foreign objects, etc. In the event of such a situation, the short circuit protection system turns off the UPS, preventing unpleasant consequences.
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Overload protection. Overload in this case is the excess of the load power consumption over the output power of the UPS. Working in this mode can also lead to unpleasant consequences up to breakage and fire; to avoid this, a protection system is installed that turns off the UPS when an overload occurs.
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Overcharging protection of external battery. The overcharge protection function prevents the accumulation of excess energy in the battery, from which the UPS operates in autonomous mode. Overcharging is highly undesirable for any type of battery. It can lead to various unpleasant consequences - from deterioration in performance to overheating and fire of the battery. The automatic protective equipment on board the uninterruptible power supply turns off the power after the battery is fully charged. This prevents “extra” curre
...nt from entering the battery, which could damage it. This system is convenient in that the battery can be left on charge for a long time without fear of overexerting it.
— Noise filtering. A system that suppresses high-frequency interference in an electrical network — these can be either single voltage surges when turning on and off powerful electrical appliances, or long-term interference from constant sources, such as electric motors. These interferences can adversely affect the operation of electronics connected to the network (up to visible failures); the noise filtering system avoids this. Such systems are quite simple, and therefore most modern UPSs are equipped with them.
— Data line protection. High-frequency interference protection system, similar to interference filtering (see above) — only used not in an electrical network, but in a telephone or wired computer (LAN) network. Such networks are also subject to interference from various sources of electromagnetic radiation, which can cause failures of equipment connected to them: PCs, printers, fax machines, etc. UPSs with this feature have at least two LAN standard connectors (input and output), into which appropriate network or telephone (with RJ-11 connectors compatible with LAN) cables are inserted.
— Emergency cut-off. This connector allows you to connect the UPS to an emergency power off system. Thus, in an emergency (for example, in the event of a fire), the entire room, including and with a power reserve, can be completely de-energized by pressing one button. Without this, the UPS would simply switch to battery when the power goes out and leave the equipment energized, which could lead to disastrous consequences.
— Sound alarm. A system that gives an audible signal in various important situations. It is most commonly used to signal a power outage and the UPS is transferring to battery power. Without a sound signal, this could not be noticed at all (the light is not always on in the room, it goes out when the network fails, the contact in the socket itself may disappear, etc.), which is fraught with a sudden shutdown of the equipment, data loss and breakdowns. Also, sound alarm can be used for other events — low battery, end of charge, bypass on / off, etc.
