Proactive attention to this often-overlooked element of UPS architecture — the UPS capacitor — can extend the value of the UPS system that protects your critical electronic systems. Here's a quick guide on what you should know about the capacitor.

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Capacitor 101
A capacitor is a fairly simple electrical
device that stores and releases electrical
energy. They can be as small as your
thumbnail or as large as a soda can —
depending on the amount of voltage
they’re expected to digest.
Proactive attention to capacitors is key to
extending the life of your UPS.

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Like batteries, capacitors degrade over
time. When a capacitor fails, there might
not be any immediate visible effects, but
other capacitors must compensate for the
additional workload, which shortens their
useful lives.

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1. Excessive current – Capacitors can be
destroyed when regularly exposed to over-
current conditions, such as steady current
that exceeds the manufacturer’s rating.
Short periods of excessive ripple current
are relatively harmless, as long as the
capacitor doesn’t have to overheat to
compensate.
What conditions influence
capacitor longevity?

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2. Over-work – Capacitors fail more
frequently if they have to filter an unusual
amount of voltage noise or frequent
transients (sharp, brief disruptions in the
sine wave.) Much like an air filter that
operates in a dirty environment, the harder
it has to work, the sooner it will have to be
replaced.

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3. Excess heat – Whether from inside the
capacitor (for instance, caused by lack of
airflow due to a clogged air filter) or from
outside (due to ambient temperature),
excess heat will eventually start to
evaporate the solution inside the capacitor
and build up unsafe pressure that can
cause failures.

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The good news is that good management
cam mitigate these risks. The biggest
factors under your control are to maintain
the recommended ambient temperature,
humidity, and cleanliness.

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Capacitor inspection during preventive
maintenance helps optimize operation
while also enhancing lifespan. Capacitor
replacement also falls into the category of
preventive maintenance, and is
recommended to insure the reliability of
the UPS against a failure and reduce the
risk of downtime.

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Download a free copy of the “Straight talk about
the capacitors in your UPS” white paper.