Anyone responsible for keeping a company’s IT infrastructure up and running understands the importance of an uninterruptible power supply (UPS). What’s not always so clear is which type of UPS is right for different kinds of applications.
In many cases, data center managers need something more robust than an offline UPS
An offline UPS or standby unit switches the critical load to battery backup any time the power fluctuates or goes out. While standby units offer surge protection and basic battery backup that can ride out brief outages, they do not provide protection from other power problems including over-voltage, line noise, and frequency variations. In addition, many basic UPS units provide a modified or simulated sine wave, which can be potentially harmful to sensitive electronics contained in IT gear, leading to decreased equipment performance and a reduction in the service life.
Organizations that can’t take any chances with their IT networks need a higher level of protection and peace of mind.
Customers that know they want something more than an offline unit often inquire about an inline UPS. While an inline UPS is not technically a UPS topology, customers usually use the term to refer to an advanced UPS.
There are two UPS topologies that can fall into this category:
- Line-interactive UPS
- Online double conversion UPS
There are several reasons why customers may want or need an advanced UPS. They may want an enhanced level of power protection between the utility power supply and the connected equipment. They may want to avoid the time delay that happens during the switch between two different lines or sources of power (i.e., from the AC mains in normal operation to the DC battery in the event of a power disruption). They may want to manage power fluctuations without constantly switching to the battery. Or they may be looking to maximize equipment availability and lifespan, making an advanced UPS that provides a pure sine wave the go-to choice.
Line-interactive online UPS units and online double conversion UPS units can both address many of these needs. Both topologies provide much greater power protection than an offline UPS. However, there are significant differences between these two UPS topologies and how they function that are important to understand. Generally, the online double conversion UPS provides superior protection, but at a significantly higher cost — up to 40% higher than line-interactive models.
A side-by-side comparison can help you better understand each type of unit so you can choose the UPS that’s right for your application.
Understanding Your Power Protection Options UPS Topology Comparison
Overview
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Provides battery backup and power conditioning for voltage regulation and enhanced protection from sags, surges, under-voltage (brownout), and over-voltage |
Provides the highest level of power quality and security for IT networks. Complete isolation from the utility power — 100% power conditioning and frequency regulation |
Power Conditioning
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Conditions power using automatic voltage regulation (AVR) and voltage boost circuitry or transformers to support and correct a wide range of input voltage fluctuations before switching to battery backup |
Conditions power through a double conversion process: AC-DC/DC-AC design converts incoming power to direct current (DC) and back to alternating current (AC) to ensure complete isolation between connected devices and utility power |
Output
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Regulates output with AVR |
Uses double-conversion technology to create a clean power supply with near-perfect output voltage and frequency regulation |
Power Protection
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Protects against the most common power problems experienced in a network and reduces the impact of spikes, surges and sags |
Fully protects sensitive equipment against everything from subtle harmonics and waveform distortion to voltage sags, spikes, brownouts, and blackouts |
Battery Transfer Time
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
4-6 millisecond break in power when transferring to battery backup prevents power drop to almost all IT devices: the inverter becomes part of the output and is always on, operating in reverse to charge the battery while AC input is normal, and switching to battery power when input fails |
Zero transfer time to batteries prevent power drop to ANY device: batteries are always online and connected to the invertor to keep the power flowing to connected devices without any interruption in the event that the main AC input fails |
Battery Life
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Drains batteries more frequently, leading to shorter battery life |
Longer battery life |
Efficiency
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Advanced models are highly energy efficient |
Less energy efficient than line-interactive models because batteries are always on |
Network Management
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Supports network management cards to enable remote monitoring and control |
Supports network management cards to enable remote monitoring and control |
Generator Compatibility
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Advanced models are compatible with many generators that provide more stable and clean output power |
Compatible with generators |
Applications
| Line-Interactive UPS | Online Double Conversion UPS |
|---|---|
|
Ideal for rackmount applications below 5,000 volt-amperes (VA) where outages are rare, but power fluctuations are common, or where protection and operating costs must be balanced Can provide surge and power protection for workstations and small office electronics Advanced models provide superior power protection for edge applications, telecom, and distributed IT equipment |
Ideal for large data centers that cannot afford any downtime and equipment that is extremely sensitive to power fluctuations Provides the highest level of power conditioning and power protection for critical IT business systems |
UPS Systems Available From Vertiv
Vertiv offers the industry’s most complete line of UPS systems including online double conversion UPS systems, line interactive UPS systems, and offline models to cover the backup power needs of your IT infrastructure and improve your uptime. A few of our most popular products include:
- Vertiv™ Liebert® GXT5 UPS. This online double conversion UPS offers premium power outage protection and continuous power conditioning in a compact and flexible rack/tower design. It is ideal for protecting critical infrastructure in both centralized and edge network applications.
- Vertiv™ Liebert® PSI5 UPS. This line interactive UPS is designed to ensure availability of critical IT applications like network closets and small data centers while protecting and extending the life of your electronic devices in schools, homes, and offices. It offers cost-effective protection from downtime and damage caused by power outages, brownouts, sags, surges, or noise interference with advanced pure sine wave output.
To learn more or view additional options, see our uninterruptible power supplies page online.
