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A three phase UPS can deliver more electrical power than a single phase supply because it uses the full three phases generated from the grid. Three phase UPS tend to be used in industrial and business settings, whereas single phase UPS systems are used for domestic appliances or lower power equipment.


Single phase UPS have a single input and output source to the electrical equipment. With just one sinewave voltage, it only requires two wires to complete the circuit, one conductor and one neutral. 

Single phase uninterruptible power supplies typically cover requirements up to 20 kVA and are used for smaller installations such as rack-mounted servers, telecoms or computer systems, and network switches, along with any device that runs directly from a standard three-pin plug.  


Three phase UPS use three separate conductors providing three sinewaves, each out of phase and spaced 120° apart from each other, to provide continuous power to the load. This means a three phase system needs a minimum of four wires (three conductors plus one neutral), which enables it to support a single phase or three phase output.  

Three phase UPS are the standard choice for larger installations with critical loads such as data centres, industrial applications, and medical environments, as well as protecting equipment with motors such as lifts, pumps, and fans.  


Single phase may also be referred to as 1 phase or 1-phase, while three phase is known as 3 phase or 3-phase. 

For UPS systems, it is common to refer to a single phase UPS by just its kVA/kW rating i.e. 10 kVA. With three phase systems, the kVW/kW rating is accompanied by the number of output phases i.e. 20 kVA (3:1) or 200 kVA (3:3) 


Key differences between single phase and three phase UPS: 

  • Number of conductors (one versus three) 
  • Number of sinewaves (one versus three) 
  • Single phase voltage is 230V, three phase voltage is 415V 
  • Single phase connection is less complicated than a three phase UPS 
  • Three phase offers higher efficiency 


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