What are Uninterruptible Power Supply (UPS) Systems?

Digital Grid

Last Updated on July 19, 2022 by Josh Mahan

An uninterruptible power supply (UPS) is an electrical device that provides power to equipment nearly instantly in the event of a failure in the power grid. Providing back electricity protects sensitive equipment from being damaged and data lost from systems that aren’t shut down correctly. 

In addition to powering equipment in complete power failures, UPS can also help mitigate power quality issues such as line noise, voltage spikes, voltage sags, and harmonic distortion.

UPS are used almost everywhere to protect sensitive electronics, either consumer or industrial, connected to the power grid.

This article will look at the three main types of UPS, their applications, and the batteries they use for backup power.

Related: Understanding N, N+1, 2N Redundancy: What’s Right for You?

What Are The Different Types of UPS?

There are three main types of UPS: Standby, Line-Interactive, and Online.

Standby UPS

A standby UPS system, also known as an offline UPS, is an uninterruptible power source that provides short-term power sourced by batteries during power outages. It is the least expensive of the three UPS system types. 

Under normal conditions, standby UPS systems receive power from the utility company via a direct AC connection. However, the standby battery system and its inverter are on hold until battery backup power is needed. Battery backup power can be needed for everyday power events like voltage surges, blackouts, and voltage sags.

When incoming electricity rises above or below set voltage levels, the standby UPS system will switch to DC battery power in milliseconds. Then, the inverter will convert it to AC to power the connected equipment.  

During more prolonged outages, the battery backup of the standby UPS allows for equipment to be shut down safely, protecting both data and equipment.

Applications for Standby UPS

Standby ups systems are best used as a short-term power source and to protect devices from power fluctuation

Typical Applications for Standby UPS include:
  • Consumer Electronics
  • Computers and PCs
  • Internet of Things (IoT) Devices
  • POS Systems
  • Security Systems

Line-Interactive UPS

A line-interactive UPS is an uninterruptible power source that can automatically regulate voltage and respond to low and high voltage conditions without draining the batteries.

Under typical situations,line-interactive systems have autotransformers that regulate low and high voltages without switching to a battery

In some instances, line-active UPS might rely on the battery to filter and regulate power. In this case, it may use its batteries more often than online UPS systems.

A line-interactive UPS can switch to battery AC power in milliseconds for outages. They are typically used in rack-mount applications below 5000 volt-ampere (VA).

Applications for Line-Interactive UPS 

Line-interactive UPS is highly effective in areas where fluctuations in power are common, and outages are rare. 

Typical Applications for Line-Interactive UPS include Critical IT Equipment Like:
  • Critical Nodes
  • Network Workstations
  • Servers
  • Network Routers
  • Larger Network Peripherals

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Online UPS

An online UPS is an uninterruptible power supply that uses a double or delta conversion technology. In the double conversion process, network equipment does not receive electricity directly from an AC outlet. 

AC power goes into a rectifier in the online UPS, where it is converted to DC power. From there, it travels to the battery, then to an inverter which converts it back to AC power connected to the equipment.

The double conversion process provides the highest level of protection by separating equipment from direct connection to utility power. It also offers clean, consistent, near-perfect power regardless of the condition of the incoming utility power.  

Applications for Online UPS

Online UPS, with its double conversion technology and zero time from the battery to equipment, is best suited for mission-critical equipment. Or in areas where power from utilities is highly unreliable.

Typical Applications for Online UPS Include:
  • Network Operation Centers (NOCs)
  • Data Centers
  • Search Data Centers
  • Medical Equipment
  • Industrial Equipment

Related: Power Usage Effectiveness (PUE): A Complete Guide

UPS Battery Types and Run Time

Today, there are three primary UPS batteries: Lithium-Ion Batteries, Valve Regulated Lead Acid (VRLA), and Flooded Cells or VLA. 

The run-time for a UPS using its batteries depends on the size and type of the batteries, the efficiency of the inverter, and the discharge rate.

Lithium-Ion Batteries (Li-ion)

Li-ion batteries are the latest batteries available and can be used in rooms without special construction laws in many jurisdictions. 

While Li-ion batteries in consumer devices have a reputation for being dangerous, commercial ones have construction and chemistry that are entirely different.  

Li-ion batteries are lighter and smaller than VRLAs and can be partially charged and recharged without battery degradation. As a result, they are expected to have longer battery life than VRLA batteries. Still, long-term data is not yet available to confirm.

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Valve Regulated Lead Acid (VLRA) Batteries

VRLA batteries are also known as sealed cells. Instead of liquid, they use a paste electrolyte that is placed and sealed in vented packaging. As a result, they charge more slowly than wet vets and can be used in any space without special protection or construction.

Warranties are typically ten years on VRLA batteries. Still, the service life is usually 3-5 years, depending on the stability of the power source in the area and how frequently they are partially discharged and recharged.  

VLRAs are not as heavy as wet cells and come in more extended life versions that cost more and must be specified when ordering.

Flooded Lead Acid Batteries

Flooded lead-acid batteries, also known as wet cells, have the most extended life of any battery, up to 25 years, but are also the most expensive

Wet cells require unique, separate, fire-rated rooms with hydrogen detection alarms, acid drains, hazmat protective gear, eye wash stations, and deluge showers. 

Flooded lead-acid batteries require regular maintenance, are the heaviest, and are used frequently on the more sophisticated and larger installations. 

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UPS Protects Critical Equipment from Power Quality Issues

UPS protects equipment from the smallest consumer devices to the most critical data centers from the catastrophic loss caused by power quality issues like outages, brownouts, and voltage surges.

The three main types of UCS, standby, line-interactive, and online, give consumers and corporations the ability to protect the equipment and machinery we use daily.

Battery technology is continually evolving, and as it does, the run time on batteries and the life of the battery continues to grow longer. 

Having the proper UPS in place can help protect your equipment and data from costly damage caused by inevitable power issues on our aging electric grid. 

Related: Data Center Power: Best Guide to Efficient Power Management

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