Power Redundancy & UPS Systems Flashcards
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Read the first 7 Power Redundancy & UPS Systems flashcards as text
Which battery chemistry is most commonly used in enterprise UPS systems due to its low maintenance and sealed design?
Answer: Valve-regulated lead-acid (VRLA)
VRLA batteries are the dominant choice in enterprise UPS because they are sealed, maintenance-free, and do not require water topping.
What effect does elevated ambient temperature have on VRLA UPS battery life?
Answer: It significantly shortens battery life; every 10°C above 25°C roughly halves the expected lifespan
VRLA battery life degrades exponentially with temperature; operating above 25°C (77°F) by 10°C approximately halves the rated service life.
In a data center with a Tier III power design, the minimum power path redundancy requirement is:
Answer: N+1 concurrent maintainability
Tier III requires N+1 redundancy with concurrent maintainability, meaning any single component can be taken offline for maintenance without affecting the load.
What is 'hot-swap' battery replacement in a UPS context?
Answer: Replacing battery modules without powering down the UPS or transferring the load
Hot-swap battery replacement allows battery modules to be removed and inserted while the UPS remains online, eliminating the need for a maintenance window.
A lithium-ion UPS battery compared to VRLA of equivalent capacity typically offers:
Answer: Longer cycle life, smaller footprint, and faster recharge, at higher upfront cost
Li-Ion batteries offer significantly more charge cycles, a smaller and lighter form factor, and faster recharge rates, though they carry a higher initial purchase price.
What does the term 'runtime' refer to in UPS specifications?
Answer: The duration the UPS can power the connected load on battery alone after utility failure
Runtime is the amount of time a UPS can support its connected load from battery power once utility or generator input is lost.
Which factor most directly determines how many battery strings should be added to extend a UPS's runtime?
Answer: The actual load in watts and the desired backup duration
Runtime is a function of battery capacity relative to the actual load; adding strings increases amp-hour capacity, extending how long the UPS can power a given watt load.