Different Types of UPS Systems

 

UPDATED: OCTOBER 10, 2024

 

by Michael Ruhe, Product Manager Engineered Solutions

We've answered the question "What is a UPS?" and why you need one to protect your business, but what types of UPS systems are available? 🤷‍♂️

 

In this blog, we'll explore the different types of uninterruptible power supply systems, how they differ in operations, and the levels of protection they provide your critical load.

 

The three most common types of UPS systems are standby (offline), line-interactive, and online double conversion.

Standby UPS

A Standby UPS, also known as an offline UPS, is the simplest type of uninterruptible power supply. But with that simplicity also comes a lack of power conditioning. 

 

During normal operation, the load is directly connected to the utility voltage through a transfer switch, allowing it to pass through unconditioned. As the power passes through, there is no voltage or frequency regulation, but there is typically some form of surge suppression that can provide protection against voltage spikes.

 

The UPS system monitors the incoming voltage and when it goes outside a specific range, or fails completely, it will switch over to battery operation. During this switch to battery operation, there will be a few milliseconds of a break in the power, so you need to know if your connected load can accommodate that.

 

Standby UPS are often used for applications that are not the most critical or sensitive such as desktop computers and other smaller equipment but do require some form of battery backup to facilitate a safe shutdown. A standby UPS is usually sized under 2kVA and can serve as a simple solution for customers requiring a low power and low-cost option.

 

 

Line-Interactive UPS

The next step up from a standby UPS is known as a line-interactive UPS. This type of UPS system provides some power conditioning in addition to surge and outage protection.

 

A line-interactive UPS will monitor the incoming voltage and either increase or decrease the output voltage using some form of voltage regulating transformer. This provides the load with a minimal form of regulated power but does not protect against any frequency variation, high noise, or harmonics.

 

Once the input voltage goes outside the range of regulation or the frequency goes outside a set range, the line-interactive UPS will switch to battery operation. Depending on how advanced the line-interactive UPS is, it could either output a simulated sine wave (square wave) or an actual sine wave output.

 

Similar to a standby UPS, a line-interactive UPS is typically applied to smaller loads. However, a line-interactive UPS may be chosen for applications that require higher quality power or are more critical to your critical to your business such as control systems or network equipment.

 

 

Online Double Conversion UPS

The UPS that provides the best protection from any type of power disturbance is an online double conversion UPS.

 

A double conversion UPS takes the incoming utility alternating current (AC) power, converts it to direct current (DC) power, and then back to AC - hence the term double conversion.

 

The UPS is continuously performing this conversion during normal operation. This is a key component of the power conditioning process, providing clean power to the critical load and ensuring that all sags, swells, spikes, frequency variations, and line noise are removed.

 

Online double conversion UPS systems are the most reliable topology since they protect the critical equipment that they serve 24/7. They are the preferred topology for mission critical applications such as data centers and can be found in sizes ranging from under 10kW all the way to 2000kW.

 

 

In closing, all three types of UPS systems perform the basic function of providing backup power in the case of an outage, but not all of them can provide the same level of power conditioning, uptime, and protection to the critical load.

 

It is crucial to understand what the cost of downtime means to your business and what your application’s needs are to determine what type of UPS system is required to back up your load.

 

When comparing line-interactive vs online double conversion UPS, if your load is critical to your operations, the choice should be an online double conversion UPS, as it will provide cleaner power, increased equipment reliability, better battery life, and less downtime.

Next Steps in Your Critical Power Journey

Selecting an uninterruptible power supply is crucial to protecting your critical infrastructure and ensuring a continuous power supply for your business’s operations. It is a major decision and investment and requires a business to consider many aspects.

 

Below is a variety of recommended resources that may help on your journey to maximum uptime. And, of course, contact us with any questions or upcoming projects. 

• Power Conditioning: More than Just Backup Power
• Minimize UPS Downtime in Critical Power System Design
• What Size UPS Do I Need? The Basics of Sizing a UPS
• UPS System FAQs

 

 

Edited by Nicole Kristof, Senior Marketing Specialist