Voltage and frequency dependent UPS or VFD UPS

means a federally regulated UPS that produces an AC output where the output voltage and frequency are dependent on the input voltage and frequency. This UPS architecture does not provide corrective functions like

those in voltage independent and voltage and frequency independent systems.

Note: VFD input dependency may be verified by performing the AC input failure test

specified in 10 C.F.R. section 430.23(aa) 2.27.1. (Appendix Y to subpart B of part 430 2.27.1.)

and observing that, at a minimum, the UPS switches from normal mode of operation to

battery power while the input is interrupted.