Ferroresonant Technology

Ferroresonant UPS systems were the first to be developed.  They are based on the inherent capabilities of the Ferroresonant transformer.  These transformers provide passive voltage regulation, using no electronics or active parts, allowing them to accept a wide range of input voltage and still maintain a constant output voltage.   In addition, their  "ride-through" capability (based on the stored energy in electromagnetic field surrounding the transformer) allows greater flexibility in inverter designs.  Ferroresonant systems typically provide the best isolation from the incoming line, since the transformer serves as a separately derived power source.  Although these systems are typically quite heavy, and efficiency leaves a bit to be desired, they are simple, easy to service and very reliable ......