In a traditional transformer-based UPS, the power flows via the rectifier, inverter and transformer to the output, with the transformer used to step up the AC voltage levels, protect the UPS from load interruption and provide current isolation. 

There are two main benefits of a transformer-based UPS. Firstly, it is generally accepted that they are more robust – there are less points of failure. Secondly, the transformer provides galvanic isolation, a separation of the input and output supplies, which protects the load from any spikes, surges, or electrical noise. 

Transformer-based UPS are the typical technology for 100 kVA and above and the choice to achieve large kW sizes or provide redundancy.  

Main benefits of Transformer-based UPS: 

• Current isolation 

• Independent mains power supply 

• Dual load protection from DC voltage 

• Providing a higher phase-neutral inverter short circuit current than a phase-phase short circuit current 

• Superior power protection when presented with power quality problems 

• Greater robustness with respect to back feed protection