Single Phase UPS Systems

20kVA/20kW is the maximum single phase output supply available from most UPS manufacturers. At 230Vac this is 87A at Unity power Factor (pF) and may be available from a 1/1 (single phase input and output UPS) or a 3/1 (three phase input and single phase output) UPS. It is not common to install a 20kVA single phase UPS unless there is a specific load requiring this.

The best way to distribute uninterruptible power to several single phase rack cabinets is via a sub-distribution board. From this device, a single cable can be run under a raised access floor or via overhead cable trays to the server rack PDU. The cable connector can include a blue Commando style connector for the rack PDUs to connect to.

In the UK and Europe the 1-phase supply is 230Vac at 50Hz. Calculate the load Amps being drawn by the IT devices to be powered from the UPS to give a total Amps and multiply this by the mains supply voltage i.e. 10A x 230Vac = 2300VA or 2.3kVA. It is also worth adding a scaling factor of 20% to allow for future expansion so 2.3kVA x 1.2 = 2.76kVA. The nearest sized UPS system to his would be a 3kVA uninterruptible power supply.

Most 1phase UPS will provide a number of rear panel IEC C14 inlets into which a power cord can be plugged. The inlet sockets are normally rated for a maximum of 10A. Some desktop standby UPS may also offer BS UK style 3-square pin or Schuko style sockets.

Single or 1phase uninterruptible power supplies up to 2kVA (2000VA) tend to use a power cord and standard plug. 3kVA and some 4kVA UPS systems (drawing up to 16A) are supplied with blue Commando style plugs. Above this power rating the uninterruptible power supply is hardwired. Below this rating, the UPS system may be converted by the UPS manufacturer or supplier for a hardwired installation and the sockets and power cord re replaced with a plate with terminals.