Voltage and frequency independent UPS or VFI UPS

means a federally regulated UPS where the device remains in normal mode producing an AC output voltage and frequency that is independent of input voltage and frequency variations and protects the load against adverse effects from such variations without depleting the stored energy source.

Note: VFI input dependency may be verified by performing the steady state input voltage

tolerance test and the input frequency tolerance test specified in 10 C.F.R. section

430.23(aa) 2.27.2. (Appendix Y to subpart B of part 430 2.27.2.) and observing that, at a

minimum, the UPS produces an output voltage and frequency within the specified output

range when the input voltage is varied by ±10% of the rated input voltage and the input

frequency is varied by ±2% of the rated input frequency.