Input voltage
The input voltage for which the UPS is designed. This parameter practically also determines the type of network — different voltages correspond to a different number of phases:
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1 phase (230 V). Connection to ordinary household networks of the 230 V standard. It is these networks that are used by most devices powered by uninterruptible power supplies: computers, video and audio equipment, gas boilers, air conditioners, medical equipment, etc. Therefore, the vast majority of modern UPSs are designed specifically for 230 V. At the same time, relatively low-power models can work directly from the outlet, but for devices with a high maximum output power — from 3.5 kVA — a special connection format (directly to the shield) may be required.
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3 phases (400 V). Connection to three-phase networks of 400 V format. Such networks are used to power powerful industrial equipment, as well as to supply energy from substations to entire segments of the power grid (for example, the entire building). Accordingly, in the case of a UPS, it makes sense to use such an input voltage only in the most powerful models designed for a significant load — for example, an entire data centre, or an industrial workshop with high requirements for process continuity. The effective output power of such “uninterruptible power supplies” is from 4 kW, and the output voltage (see below) can be either single- or three-phase.
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— 1 phase (230 V) / 3 phases (400 V). Uninterruptible devices that allow connection to any of the types of networks described above. Most of these devices are, in fact, models for three phases, supplemented by the ability to work also from 230 V. Note that for operation from a single-phase network, such models usually need to be connected directly to the shield, and the output power with such a connection may be lower the claimed maximum (this point needs to be specified separately).Input voltage range
In this case, the input voltage range is implied, in which the UPS is able to supply a stable voltage to the load only due to its own regulators, without switching to the battery. For redundant UPSs (see "Type") this range is quite small, approximately 190 to 260 V; for interactive and especially inverter ones, it is much wider. Some UPS models allow you to manually set the input voltage range.
Peak 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.Total battery capacity
The capacity of the battery installed in the UPS. For models with multiple batteries, this is both the total working capacity and the capacity of each individual battery: the batteries in such devices are usually connected in series, so that their total capacity corresponds to the capacity of each individual cell.
Theoretically, a higher battery capacity means the ability to power loads of a given capacity for longer. However, in fact, this parameter is more of a reference than practically significant. The fact is that the actual amount of energy stored by the battery depends not only on the capacity in amp-hours, but also on the voltage in volts; this voltage is often not specified in the characteristics, despite the fact that for accurate calculations it must be known. So when choosing, you should focus on more "close to life" characteristics — first of all, on the directly claimed operating time in different modes (see above).
