Choosing the optimal uninterruptible power supply (UPS) for your facility can be a complex task. There are many factors to consider when you are expanding or re-evaluating your current infrastructure, and planning to add a UPS. A few elements to examine when selecting a UPS are: availability, reliability, environment, and sensitivity of the load.

Once those parameters have been assessed, you can decide on your preferred UPS topology. All UPS’s deliver correct voltage to the load, but the differences in how they do it give us the different topologies. The three main UPS topologies available in the market today are: the Standby UPS; the Line-Interactive UPS; and the Online UPS. Here, we will break down the main configurations of each UPS topology.

Standby UPS

A standby UPS, also known as off-line or line-preferred UPS, provides a low cost solution for protection from power failures. They are generally small in size, efficient, and easy to use. The standby UPS is most commonly used in less sensitive IT applications, such as personal computing.

During normal operation, a standby UPS takes utility power and delivers it directly to the load. This means that any power anomalies from utility power do pass through to the load. When power fails, or voltage/frequency changes become too severe, the UPS transfers to battery to provide power to the load. Transfer time to battery on a standby UPS is relatively slow (longer than 4 milliseconds) and the delay can disrupt the operation of some sensitive loads.

Line-interactive UPS

A line-interactive UPS provides basic power protection at a moderate price. Like the Standby UPS, a Line-interactive UPS delivers utility power directly to the load during normal operation, which can let power anomalies through. Additionally, the Line-Interactive UPS employs a buck-boost transformer, also known as an Automatic Voltage Regulator (AVR), to manipulate the voltage to a tighter tolerance if the voltage fluctuates. This is helpful for more sensitive loads, and also prevents the battery from being used as often. If voltage falls outside of operating range or if power completely fails, the UPS transfers to battery to provide power to the load. Transfer to battery is not instantaneous. However, the transfer time for a line-interactive UPS (a few milliseconds or less) is generally much faster than a Standby UPS.

Line-interactive UPSs provide power protection against power failures, power sags, and power surges. They are designed to also protect against other power disturbances such as electrical line noise and brownouts.

Online UPS

An online UPS is designed to provide comprehensive power protection for sensitive IT loads. The online UPS consistently conditions power from the input of the UPS to the output. Utility power flows into the UPS and is converted from AC power to DC power. Then the power is converted back to AC power and delivered to the load. This completely isolates the IT load from any power anomalies which might occur from utility power and is the best choice for sensitive IT equipment. When the utility power fails, the UPS instantaneously draws its DC power from the battery. Thus, there is zero transfer time to battery in an online UPS.

One of the principal factors to consider when making an investment in an Online UPS is battery utilization. The online UPS, because of its design, uses the battery less often than the standby UPS and line-interactive UPS. This increases the life expectancy of the battery and decreases the cost of maintaining the UPS over its lifetime.

Interested in finding a UPS solution?

SEPS is proud to offer the most popular and trusted brands of uninterruptible power supplies in the critical power industry. For more information, please contact us, or speak with one of our Power Protection experts at 630-986-8899 or dmayo@sepsinc.local.