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.
Bypass (direct connection)
Bypass(by-pass) means such a mode of operation of the UPS, in which power is supplied to the load directly from an external source — the mains, diesel generator, etc. — practically without processing in the UPS itself. This mode can be activated either automatically or manually.
— The automatic bypass is a kind of safety measure. It turns on when the UPS in normal mode cannot supply power to the load — for example, when the UPS is overloaded due to a sharp increase in the power consumption of the load.
— Manual bypass allows you to enable this mode at the request of the user, regardless of the operating parameters. This may be necessary, for example, to hot-swap a battery (see below for details) or to start equipment that has a starting capacity greater than that of the UPS. Technically, it can also play the role of a security measure, but automatic systems are more reliable in this sense.
Some UPSs provide both options for enabling the bypass.
Rated output power
The effective output power of the UPS is, in fact, the maximum active power of the load that can be connected to the device.
Active power is consumed directly for the operation of the device; it is expressed in watts. In addition to it, most AC devices also consume reactive power, which is "wasted" (relatively speaking) is spent by coils and capacitors. Apparent power (denoted in volt-amperes) is precisely the sum of active and reactive power; it is this characteristic that should be used in accurate electrical calculations. See "Maximum output power" for details; here we note that when selecting a UPS for a relatively simple application, it is quite possible to use only effective power. This is at least easier than converting the watts claimed in the characteristics of the connected devices into full power volt-amps.
The most modest modern "uninterruptibles" give out
less than 500 watts.
501 – 1000 W can be considered an average value,
1.1 – 2 kW is above average, and in the most powerful models this figure
exceeds 2 kW and can reach very impressive values (up to 1000 kW or more in some industrial class UPS).
PoE output (LAN)
Availability of a LAN connector in the UPS with support for
PoE (Power over Ethernet) power supply. This technology allows energy to be transmitted via an Ethernet cable to power network devices. It is possible to power such devices directly from the UPS, which ensures equipment backup in case of power supply interruptions. Such devices include IP video surveillance cameras, access points, various sensors, etc.
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).
