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ITFrequently Asked Questions · UPS
What is the difference between a single-phase and a three-phase UPS?
Single-phase UPS units are used mainly in residential and small business applications, while three-phase UPS units are designed for larger loads, such as in industry or data centers.
The difference starts with the electrical supply. Most homes and small offices have a single-phase 230 V supply, while buildings with higher power needs, such as factories, hospitals and server rooms, have a three-phase supply (400 V between phases). The UPS must match the supply at its input and the loads it will power at its output.
Single-phase UPS units typically cover a few hundred VA up to a few tens of kVA. Three-phase units usually start at around 10 kVA and go up to hundreds of kVA, spreading the load across three phases. There are also models with three-phase input and single-phase output (3/1), useful when a building has a three-phase supply but the loads are single-phase.
Practical tip: before choosing, check the electrical panel and note whether there are three-phase loads, such as motors or large air-conditioning units. A common mistake is connecting a large single-phase UPS to just one phase of a three-phase supply, which unbalances the load between the phases. In such cases, ask an electrician for advice.
