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ITGlossary · Electrical units
Volt (V)
The unit of electrical voltage; in Europe mains voltage is 230 V single-phase and 400 V three-phase.
Technical level:Basic
The volt expresses the potential difference that pushes current through a circuit, somewhat like water pressure in a pipe. In Greece the nominal mains voltage is 230 V single-phase and 400 V between phases in three-phase systems, with a permitted deviation of about ±10%.
In UPS units, voltage appears in many places in the specifications: input voltage and operating range, output voltage and its accuracy, and battery string voltage (for example 12, 24, 36 or 48 V DC in small models and much higher in large ones). The string voltage results from the number of 12 V batteries connected in series.
When adding external batteries, the string voltage must match exactly what the UPS accepts. The wrong voltage can cause serious damage.
Related articles
Related terms
- Noise (Electrical)Unwanted high-frequency disturbances on the supply voltage, e.g. from motors or power supplies, which UPS systems and line conditioners filter out.
- Single-phase PowerAn electrical system with one alternating current (AC) voltage phase, commonly used in homes and offices.
- Three-phase PowerA supply with three AC phases shifted by 120° (400 V between phases), used for large loads, motors and UPS systems from about 10 kVA.
- TransformerAn electrical component that changes voltage levels or isolates circuits.
- DC VoltageRefers to the direct current (DC) voltage level, typically that of a UPS battery.
- Hardwired (Terminal Block) ConnectionPermanent connection of the UPS input or output by an electrician, with cables screwed into a terminal block instead of plugs and sockets, usually on higher-power UPS units.