| Uninterruptible power supplies (UPS) play two | | | | of extra battery packs and an external standby |
| important roles in power protection: 1) providing a | | | | power source, such as a diesel generator or fuel cell. |
| source of standby power in the event of a mains | | | | The transformer-based UPS system |
| failure and 2) conditioning mains electricity to remove | | | | While many UPS are transformerless, organizations |
| power problems such as sags, surges, brownouts and | | | | reliant on larger datacenter and voice networks, |
| fluctuations that can damage equipment, cause | | | | industrial processes, security or hospital applications, |
| computers to lock, fail or crash and lead to data loss | | | | often require transformer-based uninterruptible power |
| or corruption. There are different types of UPS for | | | | supply. This gives greater robustness, albeit with slightly |
| different types of power protection requirement. This | | | | lower efficiency and greater heat and noise |
| article explains what they are and where they fit in. | | | | generation. |
| A UPS sits between mains power supply and ‘the | | | | As to the role each type of uninterruptible power |
| load’ (equipment and systems in a building or | | | | supply plays in power protection implementations, |
| datacenter that need a continuous source of | | | | choice is down to load category, load size and the |
| electricity). At its simplest, a UPS conditions electrical | | | | level of resilience required and the need for |
| current, converts it from AC to DC, and negates | | | | redundancy. UPS systems are grouped by |
| potentially harmful power problems. In the case of a | | | | manufacturers like Riello UPS into specific applications |
| total mains failure, the UPS powers the load from its | | | | such as: IT, network, industrial, enterprise and |
| back-up battery until another energy source starts up | | | | rackmount. |
| or mains is restored. Put simply, an uninterruptible | | | | ICT Environments |
| power supply can be the difference between life and | | | | IT typically covers smaller applications (300VA – |
| death for some businesses – particularly given | | | | 3kVA); information and communications technology |
| today’s demand-driven, energy-hungry | | | | (ICT) typically, including home PCs, small office/home |
| environments. | | | | office and data and voice networks. |
| Different types of UPS | | | | UPS for this type of application include off-line, line |
| There are three conventional types of uninterruptible | | | | interactive and on-line designs up to 3kVA. On-line |
| power supply: | | | | uninterruptible power supplies in this range are |
| - Online or Double Conversion | | | | transformerless so as to achieve a small footprint, |
| - Line Interactive | | | | minimal weight and low noise and heat output. They |
| - Offline (or Passive Standby). | | | | are usually located in computer rooms, next to |
| | | | | protected equipment. However, their reduced size |
| An Online or Double Conversion uninterruptible power | | | | means fewer output sockets, so in highly populated |
| supply maintains voltage and frequency variations | | | | environments a greater number may be required, |
| within prescribed limits so that output is independent of | | | | which will have an impact on capital and operating |
| fluctuations in supply. Alongside conditioning mains | | | | costs. |
| power to negate problems, this is the only UPS solution | | | | Network Applications |
| that provides break-free supply to the plant or | | | | Network applications are typically 3kVA to 80kVA. |
| datacenter during a power cut. | | | | Corporate data and voice networks such as those run |
| A Line Interactive UPS uses built-in passive electronic | | | | by ISPs (internet service providers) and |
| regulation devices to stabilize and regulate voltage | | | | telecommunication companies fall into this category. |
| fluctuations. When mains supply is present, the output | | | | Uninterruptible power supply for this type of application |
| frequency of the UPS tracks the input of the mains. | | | | are transformerless, which, again, minimizes size and |
| Line Interactive and On-Line UPS use tower or | | | | weight. They act as a centralized power source and |
| ‘rackmount’ case formats and sit next to their | | | | are hardwired at both input and output due to the high |
| respective loads, typically in a datacenter or computer | | | | levels of power required. The UPS may also require |
| room. | | | | connection to a three-phase incomer. The loads |
| An Off-Line or Passive Standby UPS is the type that | | | | themselves are more likely to require three-phase and |
| is typically used to protect single PCs. It is compact, | | | | dedicated power distribution switchgear. |
| designed for desktop or wall mounting and uses its | | | | Industrial and Enterprise |
| own output to track voltage and frequency variations | | | | Industrial or enterprise applications, upwards of 10kVA, |
| in the mains supply power so it is primed and ready to | | | | are usually for enterprise-wide data and voice |
| power the load for a short duration (10-15 minutes) | | | | networks, industrial processes, security (emergency |
| from its built-in battery in the event of a power cut. | | | | lighting, fire and security systems) and large hospital |
| Most power cuts last for less than a few seconds, | | | | applications. They are transformer-based and will have |
| which means the load is protected by this type of | | | | either a 6-pulse or 12-pulse rectifier fitted as standard. |
| uninterruptible power supply. In the case of an | | | | The transformer provides robustness but with slightly |
| extended power failure, this type of UPS is designed | | | | lower efficiency and higher heat and noise generation. |
| to perform a controlled shutdown of equipment to | | | | Rackmount Applications |
| negate potential damage but it is not designed to | | | | Rackmount applications start from around 700VA all |
| provide extended runtime. | | | | the way up to 30kVA. Rack cabinets have become a |
| Extended Uninterruptible Power Supply Benefits | | | | common installation format for multiple server projects |
| Larger uninterruptible power supplies can work in | | | | to reduce space and cable runs in computer rooms. |
| parallel to improve system resilience, MTBF (mean time | | | | Manufacturers of uninterruptible power supplies have |
| between failure) and availability. | | | | responded by creating rackmount UPS formats from |
| For a network-sized uninterruptible power supply, the | | | | standard product ranges. UPS can be installed in racks |
| installation of an external UPS maintenance bypass | | | | that are strong enough to take their weight. A typical |
| enables routine or emergency maintenance to be | | | | rack cabinet has a loading of 150-300kg. In this |
| carried out (without supply disruption) during normal | | | | instance, the UPS often sits next to battery packs |
| working-hours. | | | | (part of the power protection installation) and protected |
| Extended runtime (the time a load is running on | | | | loads. Sometimes UPS and batteries will have their |
| back-up power) can be acquired using a combination | | | | own, dedicated rack. |