Extreme Networks ExtremeSwitching 5520 Series Hardware Installation Manual page 50

UPS (Uninterruptible Power Supply) Requirements
A UPS traditionally can perform the following functions:
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Absorb relatively small power surges.
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Smooth out noisy power sources.
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Continue to provide power to equipment during line sags.
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Provide power for a period of time after a blackout has occurred.
In addition, some UPS devices or UPS-plus-software combinations provide the following functions:
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Automatically shut down equipment during long power outages.
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Monitor and log power supply status.
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Display the voltage (current draw) of the equipment.
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Restart equipment after a long power outage.
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Display the voltage currently on the line.
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Provide alarms on certain error conditions.
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Provide short-circuit protection.
Selecting a UPS
To determine UPS requirements for your switch, answer these questions:
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What are the amperage requirements?
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What is the longest potential time period that the UPS would be required to supply backup power?
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Where will the UPS be installed?
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What is the maximum transition time that the installation will allow? (See
Transition Time
Note
We recommend that you use a UPS that provides online protection.
Calculating Volt-Amperage Requirements
To determine the size of UPS that you need:
1. Locate the voltage and amperage requirements for each piece of equipment.
These numbers are usually found on a sticker on the back or bottom of your equipment.
2. Multiply the numbers together to get Volt-Amperes (VA):
VA = Volts x Amperes
3. Add the VA from all the pieces of equipment together to find the total VA requirement.
To determine the minimum volt-amperage requirements for your UPS, we recommend that you add
30% to the total.
Providing a Suitable UPS Transition Time
UPS transition time is the time required for the UPS to change from providing AC power derived from
the utility (or mains) supply to providing AC power derived from the battery backup. UPS transition
time is sometimes called UPS transfer time.
UPS transition times vary between UPS models and implementations, but shorter transition times are
preferred. For Extreme Networks stacking products, we recommend a UPS transition time of 20
milliseconds or less to ensure optimum performance and minimize service interruptions.
50 ExtremeSwitching 5520 Series Hardware Installation Guide
on page 50.)
Site Preparation
Providing a Suitable UPS