Uninterruptible Power Supply (UPS)
Dec. 5, 2011 - Jim Bernstein
Everyone at some time or another has been affected by a blackout or a power surge and had their computer either shut off or crash because of either the power being lost completely or just enough to cause an issue with it running normally. There are ways you can avoid these kinds of problems and keep your computer going even when the power is not.
An Uninterruptible Power Supply is a device that sits between the wall outlet and a device such as a computer to prevent undesired power effects such as outages, sags, surges, spikes, etc. A UPS includes a battery to maintain power in the event of a power outage. The UPS can keep a computer running for several minutes after a power outage which will let you save data and shut down the computer properly. UPS units come in sizes ranging from units which will backup a single computer to units which will power entire buildings.
There are two common UPS systems in use today, standby UPS and continuous UPS.
In this type of UPS, power is usually obtained directly from the power line, until the power fails. After power failure, a battery powered inverter turns on to continue supplying power. The batteries are charged when line power is available. Standby UPS systems are more common for small business or home use of their smaller size and lower cost.
Line Interactive or Online
This type of UPS continuously operates from an inverter and there is no switchover time because it doesn't have to make the switch from AC to batter. These units generally provide the best isolation from power line problems. They cost more, have increased power consumption, and increased heat generation.
A UPS performs the following functions:
- Absorbs relatively small power surges
- Smooth out noisy power sources
- Provide power to equipment during line sags
- Provide power for a time period after a blackout has occurred
Some UPS units have software that can provide the following functions:
- Perform an automatic shutdown and restart of equipment*
- Monitor the status of the power supply
- Display the Voltage/Current draw of the equipment
- Provide alarms for certain error conditions
- Provide short circuit protection
- Display operating temperature
- Display battery strength
*A UPS attached to a file server usually requires an additional cable that alerts the file server when the UPS is running on standby power. The server will then proceed with shutdown procedures.
Typical home or small business UPS (Front and rear)
When purchasing a battery backup system, you need to know the following about the devices:
- The VA rating. The VA rating is the maximum number of Volts it can deliver.
- Battery life - How long they will provide power and when they need to be replaced
- If the UPS has a warning system to notify the server when the UPS is operating on standby power
- Whether the UPS includes any power conditioning features to protect your equipment
- If the device warns you when the batteries can no longer provide backup power
You will also need to know the power requirements of the devices you'll hook to the UPS.
How to Configure an Uninterruptible Power Supply (UPS) device in Windows XP
Surge Suppressors and Protectors
Replacing a Power Supply