Power FAQs

Why the need for power protection?

Integrated power management - Discover what you've been missing.

Reason #1: Utility companies

Utility power isn't clean.
Mainly because it doesn't have to be. By law, it can vary widely enough to cause significant problems for your equipment.

Utility power isn't 100% reliable.
In the U.S., it's 99.9 percent reliable, which translates into a likely nine hours of total downtime every year. Just from issues at the power company.

Even short outages can be trouble.
Losing power for just 10 seconds can trigger events that may require 15 minutes or possibly hours to get equipment back online.

Reason #2: The problems and risks are intensifying

High-tech equipment is highly sensitive.
Computing and networking components are more vulnerable than ever to power problems. As technology improves, high-density servers are doing more, which puts more at risk.

Availability is everything.
If IT systems go down, the entire enterprise can't function.

Downtime is costly.
Some industry estimates believe the U.S. economy loses between $200 billion and $570 billion a year as a result of outages and other disturbances.

Reason #3: Generators and surge suppressors are not enough

Generators only work when the power's off.
Backup generators address outages but provide no protection from the other power disturbances.

You need more than a surge protector.
Surge suppressors take care of power surges but provide no protection from under-voltage, variance conditions and other power problems.

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What does a UPS do?

A UPS performs three primary functions:

First, a line-interactive or double-conversion UPS conditions the incoming dirty power from the utility company. It filters out the irregularities and gives you clean, uninterruptible power.

Second, it provides ride-through power to cover for sags or short-term outages (3 minutes to several hours, depending on what you need).

Finally, it enables seamless system shutdown during a complete power outage.

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How do I choose the right UPS?

There are four different kinds of UPSs:

Standby UPSs — These smaller UPSs provide an economical source of protection from power outages, surges and sags. If you just need basic protection for small systems like desktops and cash registers, a small standby UPS like the Eaton 3S is your best choice.

Line-interactive UPSs — If you need voltage regulation and power protection for moderate loads (500 VA to 6 kVA), particularly for commercial or office applications, a line-interactive UPS like the Eaton 5P or Eaton 5S is your best bet.

Double-conversion UPSs — These UPSs convert raw power coming in to refined power by changing it from dirty AC to DC, clean it and then convert it back to AC. For very sensitive, expensive equipment that needs clean, true sine-wave power, a double-conversion UPS like the Eaton 9PX or Eaton 93PM is the smart pick.

Double-conversion on demand — If you must have clean power for high-density data centers, and energy efficiency and flexible configuration are top priorities Eaton's innovative, hybrid double-conversion on-demand (exclusive to the Eaton BladeUPS) would be the only choice. It combines line-interactive and online modes.

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What are the nine power problems?

In an ideal world, your wall socket would provide an infinite stream of perfect power, at constant voltage and cycling exactly the same number of time per second. Don’t count on it.

  1. Power failure. When a superhero loses his ability to fly or a total loss of utility power.
  2. Power sag. Post-lunch sleepiness or short-term low voltage.
  3. Power surge (spike). Rush of energy following a double shot of espresso or short-term high voltage more than 110 percent of normal.
  4. Under-voltage (brownout). When your amp’s too wimpy to handle the bass line or reduced line voltage for an extended period of a few minutes to a few days. Often happens during the summer months when everyone is cranking up their air conditioners.
  5. Over-voltage. Inhuman cheerfulness exuded by aerobics instructors or increased line voltage for an extended period of a few minutes to a few days.
  6. Electrical line noise. Excuse you use to get off the phone quickly or a high power frequency power wave caused by radio frequency interference (RFI) or electromagnetic interference (EMI).
  7. Frequency variation. Fluctuation in how often you do laundry from week to week or a loss of stability in the power supply’s normal frequency of 50 or 60 Hz.
  8. Switching transient. Breaking up with your significant other only to get back together every six months or instantaneous under-voltage in the range of nanoseconds.
  9. Harmonic distortion. “Music” blaring from your nephew’s headphones or the distortion of the normal power wave, generally transmitted by unequal loads.

Here is a visual aid to help better illustrate these nine power problems.


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What is the difference between single and three-phase power?

Three-phase power, the most efficient way to distribute power over long distances, allows for large industrial equipment to operate more efficiently. It’s characterized by three single-phase waves that are offset in their phase angle by 120 degrees, or one-third of the sine wave period as illustrated in Figure 1. Three-phase voltage can be measured from each phase to neutral or from one phase to any other. The voltage relation between phase-to-neutral and phase-to-phase is a factor of the square root of three (e.g., 120V versus 208V).


Put simply, three-phase power:

  • Is common in most large businesses and high-density data centers with higher kVA and rack applications
  • Is used for applications requiring greater than 1000 watts
  • Is used to balance the loads on the utility power of the building
  • Is safer and more cost effective to run
  • Is delivered in a steady stream at a constant rate


Conversely, single-phase power is distributed through common household outlets to power everyday equipment such as laptops, lighting and televisions. When looking at an oscilloscope image of the voltage coming out of a single-phase outlet as illustrated in Figure 2, there’s only a single wave. Single-phase power is obtained by simply using only one phase of a three-phase system. Its root mean square (RMS) voltage is 120V (for North America) and it oscillates between its peaks of ±170V at 60 Hz (or 60 times a second).


Single-phase power:

  • Is used in most residential homes and small businesses
  • Is used for a wide range of general applications
  • Is the standard for locations where three-phase power is unavailable
  • Is the most efficient for units up to 1000 watts
  • Is not delivered at a constant rate


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What is the difference between a decentralized configuration and a centralized configuration?

In a centralized UPS configuration, a larger UPS supports multiple locations or a group of equipment from a single point. Centralized UPSs are often hardwired into an electrical panelboard.

A decentralized configuration allows each UPS to protect a handful of devices or a single piece of equipment. Decentralized UPSs are usually plug and play using plugs and receptacles.


Dive deeper into backup power FAQs by downloading the free UPS handbook.

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