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Table Of Contents  CertiGuide to A+ (A+ 4 Real)
 9  Chapter 11: Power Supplies, Surge Protection and Uninterruptible Power Supplies
      9  Uninterruptible Power Supplies (UPSes)

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UPS Types

Standby Power142This type of system allows the AC power to be connected to the device normally. The UPS circuitry constantly monitors the AC power. If incoming AC power fails, the UPS automatically switches to the battery powered inverter source.

The standby power supply is the least costly; however, there are some disadvantages. There is a transition period between the loss of AC power and engagement of the backup power. This creates a problem for computer systems, due to the momentary loss of power.

The standby power supplies do not provide power regulation. This means that if rises and dips on the AC voltage occur, the device will receive them. This may include surges and noise generated by other appliances on the same circuit.

Intermediate143This UPS interacts with the AC power. The intermediate UPS has the ability to regulate the AC line voltage. This is accomplished through power conditioning, allowing the intermediate UPS to assist with AC line voltage regulation of the output. However, like the standby UPS, the AC voltage may still allow surges and noise to reach the devices.

On-Line144With an on-line UPS, the AC power is used to create DC voltage and charge the battery on the UPS. All power for the connected device is manufactured through the inverter.

An on-line UPS regulates all AC power in the conversion process. Brownouts, dips, sags, and noise, are prevented from passing through to the computer. There is no transition time between AC and battery power since the battery and inverter are always in use. There is never a direct connection between the AC power and the computer.


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142. http://www.strathfield.com.au/glossary.asp?Index=U&glossid=337

143. http://www.iter.org/ITERPublic/ITER/PDD3-4.pdf

144. http://www.exeloncorp.com/comed/library/pdfs/sppqups01.pdf

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Uninterruptible Power Supplies (UPSes)
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