UPS Topology – Line interactive vs Online Double Conversion

There are two main UPS topologies, line interactive and online double conversion. We are going to explain these and assist you to select which one would be best for your application.

This information is broken down into two parts; the layman definition, written by myself (I have a marketing and sales, non-technical background) and a technical definition, which we will be explained by our technical manager.

Line-interactive, the load is always running off the mains power, when the power is cut there is a short change-over time to the batteries (approx. 6ms) Line-interactive the power always go through and AVR and Surge protection before the load, thus the power is still being “cleaned”.

Online, the load is always running off the batteries, so we always have a controlled frequency (50Hz) and AC output (230V AC). There is no change over time with online for it is already on the batteries.

Overall, short change over does not affect most equipment (CCTV, basic computer equipment) , however online UPS is preferred for more expensive and sensitive equipment like servers and medical scanners.

Below is a diagram to demonstrate the difference between how a line interactive UPS “cleans the power” vs and online UPS. Please note if you are after a more technical diagram we do have this below.

Line-Interactive, during normal operation the mains supply is fed via an automatic voltage regulator (AVR) to feed the load. The AVR regulates the mains supply voltage, boosting if low or bucking if high. The mains supply is used to charge the batteries. When the AC goes out of the specified range, the load is switched to the inverter that draws its power from the batteries.

Online double conversion, converts the power twice, so during normal operation the mains supply is converted from AC to DC, the DC is then converted to AC that feeds the load. When the mains supply goes out of a specified range, there is no switching, and the UPS simply draws its power from the batteries.

If you require any further assistance in selecting the correct UPS for your application, please contact one of our technicians 1300882447 or sales@pssdistributors.com.au