voltage and frequency dependent (UPS) (VFD)

Voltage and Frequency Dependent(VFD) is a classification ofUPS systems that states that these systems are relatively dependent on voltage changes and frequency changes.

Voltage and Frequency Dependent (VFD) is described in the EU standardEN 50091-3 and is part of UPS protection class 3.

VFD devices offer only a low level of protection. This UPS protection class includes passive filters, simple UPS devices for offline operation and standby operation. In the event of faults, these UPS devices switch to battery operation after a few milliseconds. VFD systems do not react to transient peaks and short-term overvoltages that are within the tolerance period. The protective effect of these systems is low.