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Jai Ganesh

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Registered: 2005-06-28

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Uninterraptable Power Supply

Uninterruptible power supply

Gist

An uninterruptible power supply (UPS) is a device that allows a computer to keep running for at least a short time when incoming power is interrupted. Provided utility power is flowing, it also replenishes and maintains energy storage. A UPS protects equipment from damage in the event of a power failure.

A UPS (Uninterruptible Power Supply) is used to provide backup power and protect electronic devices from power interruptions and fluctuations. It's essentially a battery backup that kicks in when the primary power source fails, ensuring devices continue running without a sudden loss of power.

Summary

An uninterruptible power supply (UPS) is a device that allows a computer to keep running for at least a short time when incoming power is interrupted. Provided utility power is flowing, it also replenishes and maintains energy storage.

A UPS protects equipment from damage in the event of a power failure. It is used in any situation where electrical equipment is sensitive to power loss or issues with power quality, for example, if a system experiences unsafe changes in voltage output. UPSes are typically used in settings pertaining to computer systems, data servers or industrial devices, or in settings with mission-critical equipment, such as medical and laboratory systems.

Energy can be stored in different ways. Rechargeable batteries are the most common. For simplicity, the examples and illustrations here are based on that technology. However, kinetic energy can also be stored in heavy, rotating flywheels or energy can be stored as fuel.

The more energy stored, the longer backup power can be maintained, with practical limitations that will be discussed later. The differences among UPS systems lie in the technology that enables them to do their jobs.

How does a UPS work?

A battery-powered UPS typically contains the following components:

* Rectifier or charger. This converts alternating current (AC) to direct current (DC) and directs it to feed the inverter or to charge the battery.
* Inverter. This converts the electricity from DC into AC.
* Batteries. These are either lithium-ion, concerned about orderly shutdowns lead-acid (VRLA), flooded lead-acid or nickel-cadmium batteries.
* Static and maintenance bypass. This provides an alternative path for power to flow in the case of a UPS failure or overload.
* Control unit. This manages and coordinates the functions of a UPS, including monitoring system status, switching between power sources and regulating output voltage and frequency.

A UPS is typically plugged into an AC outlet and activates when it detects a power outage, voltage drop, surge or frequency variation. In the case of an outage, the UPS almost immediately switches to the battery -- fast enough so no electrical equipment is damaged. From there, the battery acts as a continual emergency power source until it uses all its power.

Depending on its size, a UPS can protect a single computer or a whole data center. Its stored power might last from a few minutes to several hours. The goal is to either last until generators are turned on or until protected devices are properly shut down.

Details

An uninterruptible power supply (UPS) or uninterruptible power source is a type of continual power system that provides automated backup electric power to a load when the input power source or mains power fails. A UPS differs from a traditional auxiliary/emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions by switching to energy stored in battery packs, supercapacitors or flywheels. The on-battery run-times of most UPSs are relatively short (only a few minutes) but sufficient to "buy time" for initiating a standby power source or properly shutting down the protected equipment. Almost all UPSs also contain integrated surge protection to shield the output appliances from voltage spikes.

A UPS is typically used to protect hardware such as computers, hospital equipment, data centers, telecommunications equipment or other electrical equipment where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss. UPS units range in size from ones designed to protect a single computer (around 200 volt-ampere rating) to large units powering entire data centers or buildings.

Common power problems

The primary role of any UPS is to provide short-term power when the input power source fails. However, most UPS units are also capable in varying degrees of correcting common utility power problems:

* Voltage spike or sustained overvoltage
* Momentary or sustained reduction in input voltage
* Voltage sag
* Noise, defined as a high frequency transient or oscillation, usually injected into the line by nearby equipment
* Instability of the mains frequency
* Harmonic distortion, defined as a departure from the ideal sinusoidal waveform expected on the line

Some manufacturers of UPS units categorize their products in accordance with the number of power-related problems they address.

A UPS unit may also introduce problems with electric power quality. To prevent this, a UPS should be selected not only by capacity but also by the quality of power that is required by the equipment that is being supplied.

Additional Information:

What Is Uninterruptible Power Supply or UPS

An uninterruptible power supply (UPS) or uninterruptible power system is an electrical unit that provides power for computers, telecommunication equipment, etc. It not only offers emergency power backup but also protects the devices in use.

The reason why UPS system proves to be essential is that the mains electricity supply can be somehow unreliable. The input power source may fail aperiodically, resulting in communication outage and data loss. Moreover, problems like voltage spike, voltage sag, noise, harmonic distortion also affect the quality of mains power. To protect device security and ensure working efficiency, an uninterrupted power supply can be a credible assurance.

How Does Uninterruptible Power Supply Work?

Unlike a common emergency power system or standby generator, an uninterruptible power supply can provide nearly instantaneous protection from input power interruptions by using the energy stored in the batteries.

The four main functional components of a UPS system are batteries, inverter, rectifier, and static bypass switch. A battery is the heart of a UPS power but can be also the main source of UPS failure. A UPS rectifier performs two important roles: converting the input utility power from AC (Alternating Current) to DC (Direct Current) and recharging the batteries while DC power routes to the inverter. Then the inverter converts DC power from the rectifier (or batteries) back into AC power for load use. The static bypass switch allows utility AC power to flow directly through the UPS to the load, bypassing UPS components, providing a vital defense line in the event of a UPS failure.

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