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Knowledge is Power: The Importance of Understanding The Main Components of Your UPS

Although at times ignorantly relegated as merely a “battery in a box,” uninterruptible power systems (UPS’s) are in fact complex devices that perform multiple functions — not the least of which is ensuring clean power and continuous up time to sensitive electronic equipment.

Yet without proper maintenance, UPSs are subject to failure, since critical components will wear out from normal use.

Engaging in regular service performed by trained and experienced personnel can greatly minimize the risk of failure, as can another simple act:  bolstering your own power system knowledge.

In fact, understanding how the key elements of your UPS work will enable you to more easily identify — and avoid — potential problems. Here, we examine four primary components:

Battery — As the heart of any UPS system, batteries are tasked with supporting the connected load during a utility power failure.

Although it is the most critical component in UPS reliability, the battery is often ignored as a maintenance-free product that doesn’t require much attention or inspection — a mistake that can prove costly and potentially devastating.

Every battery system contains at least one string, and depending on the UPS configuration, multiple strings may be added to increase run time and/or redundancy.

Yet because the strings are connected in a series, if a single battery goes bad, it can cause the entire string to fail. Studies show that up to 20 percent of UPS failures can be attributed to bad batteries, which further underscores the need for regular inspection and maintenance regardless of their age.

A valve regulated lead acid (VRLA) UPS battery typically has a life expectancy of four to six years, although individual quality and charging technology can impact the projected lifespan.


Rectifier — A UPS rectifier performs two very important roles: charging the batteries and converting incoming utility power from AC to DC.

Depending on the UPS manufacturer, the batteries may be trickle charged, which keeps them maintained at the proper float voltage but can subject them to electrode corrosion and electrolyte dry-out.

Other manufacturers utilize a more sophisticated method that prevents unnecessary charging, thus significantly slowly wear-out.

Inverter — The inverter within a UPS accepts the DC from the DC buss, which is supplied by the rectifier and the battery.

During a power outage, the rectifier will no longer provide current to the D/C buss, leaving the battery to support the load.

But if power is not restored before the batteries wear out, the system runs the risk of dropping the load unless an external power source such as a generator kicks in.

Static bypass — A UPS’s internal static bypass circuit provides an important line of defense in the event of a UPS failure.

This component automatically closes the circuit and allows the incoming power to divert around the rectifier, batteries and inverter.

Although the power supply is not conditioned, the static bypass lets critical systems continue functioning even if the UPS’s internal components fail.

Now that you’re familiar with the primary components of your UPS, you are in a position to make more educated decisions to keep your system optimally performing.

To begin, we recommend scheduling at least two preventative maintenance (PM) visits per year.

These service calls, which include a comprehensive range of inspections, are designed to ensure the ongoing health of the critical components outlined in this blog.

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