Typical examples would include ATMs, small lab equipments, desktop computers, file servers, switches, routers, hubs and telecoms systems. The wall sockets that we typically plug into are single phase supplies rated at 230Vac 50Hz in India. This is in contrast to a decentralised power continuity plan using a number of smaller UPS dispersed to protect clusters of loads like computers and lower power equipment (<10KVA) within a facility. Using a three phase UPS system can simplify a power continuity plan and allows a site to adopt a centralised power protection plan, where one large UPS is used to protect a complete building or critical circuits and operations within it. If the loads are single phase we may need a 3/1 configuration. If the loads are three phase as well, then we require a 3/3 configuration. Three phase circuits may be required throughout the building to carry the large amounts of electrical power required for large KVA three phase This is a generalisation as many environments can include both single and three phase loads of course.įrom a UPS systems perspective, if we are to connect the UPS to a three phase supply we require a UPS with a 3/x configuration. Most datacentres, commercial and industrial buildings will have a 3 phase electrical incomer that connects them via a local distribution transformer to the Mains. However for a three phase UPS it is common to refer to the KVA/KW rating along with the number of phases i.e. In the world of UPS, it is common to refer to a single phase UPS only by its KVA/KW rating i.e. This is due to the output amperage and cable requirements. A 10KVA output is generally the largest single Phase UPS system available. The laws of physics and Ohms Law also come into play, meaning that cable sizes also increase in diameter as amperages rise. A 3 phase supply can deliver more electrical power than a single phase supply. This is because a 3 phase mains or generator supply actually consists of three single phase supplies (and a neutral) with a 120 degree phase orientation between them. In UPS there are three potential phase configurations available. It also helps to determine whether to offer a three phase or single phase UPS system. This not only builds up a complete picture of the electrical circuits on-site. Even when the consumer has a three phase connection, the choice of three phase or single phase UPS depends on several factors like the loads to be connected to UPS and also electrical distribution within the facility from the building incomer, electrical switchgear and distribution units to the room the loads to be protected are within. Only if expected load is below 5-7KW, then the consumer gets a single Phase connection. Most consumers of electricity in India have a three phase mains connection if the total load is more than 5-7 KW. Each phase reaches its peak 120 degrees apart from the others so the level of power supplied remains consistent Single Phase power is used in most homes and small businesses and adequate for running lights, fans, 1 or 2 ACs, some computers and motors up to about 5 horsepower a single phase motor draws significantly more current than the equivalent 3-Phase motor, making 3-Phase power a more efficient choice for industrial applicationsįigure-2 3-Phase power has 3 distinct wave cycles that overlap. All of these factors play into the sizing of the UPS and the selection of the type of the UPS Selection of UPS 3 Phase or 1 Phase It is important to determine the acceptable delay between loss of primary power and availability of UPS power, the length of time that emergency or backup power is required, and the criticality of the load that the UPS must bear. Some facilities need an UPS for more than one purpose. UPS may be needed for a variety of purposes such as lighting, startup power, transportation, mechanical utility systems, heating, refrigeration, production, fire protection, space conditioning, data processing, communication, life support, or signal circuits. Prior to selecting the UPS, it is necessary to determine the need.
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