Max. current
The maximum current drawn by the UPS. In fact, the current reaches its maximum value only when the UPS is operating from the mains with maximum load power and a completely discharged battery. However, when calculating the load on the power grid, this parameter should be taken into account.
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.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).
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).
Fuse
Fuses are used to protect the UPS from a critical increase in current strength: at the right time, they open the circuit, preventing unpleasant consequences. Today, these types of fuses are used.
— Melting. At a critical current strength, the conductive element in such a fuse melts and opens the circuit. The fusible protection is disposable, after operation such a fuse must be replaced.
— Automatic. Such a fuse has a sensor that monitors the current strength and opens the contacts at the right time. Its main difference from fusible is reusability: after operation, the circuit can be closed again with literally one press of the button on the fuse.
Operating temperature
Ambient temperature range in which the UPS is guaranteed to maintain normal operation.
All modern "uninterruptible" without problems endure the temperatures typical for residential and office premises. Therefore, it makes sense to pay attention to this parameter if the device is planned to be used in more extreme conditions — for example, in an unheated room, or vice versa, in a production workshop with a high air temperature. At the same time, it's ok to take a margin for temperature: this will give a guarantee in case of unforeseen situations, besides, the wider the temperature range, the higher the overall resistance to adverse conditions.
Noise level
The maximum noise level produced by the UPS during operation. A noise of 30 dB approximately corresponds to a loud whisper, 40 dB to a conversation at a distance of several metres (it is models up to 40 dB that can be considered
quiet UPS), 50 dB is considered the maximum noise level that does not create discomfort. The redundant power supplies are the least noisy, and inverter power supplies are the noisiest (see "Type"). In general, the lower the noise level, the more comfortable the use of the UPS, however, for devices installed in offices where people do not stay permanently (for example, server rooms), this parameter is not critical.
