Online UPS (VFI / Double-Conversion) UPS Topologies

“Voltage and frequency independent” UPS in compliance with IEC 62040-3, as well as online or double conversion, offers superior protection against problems in the power supply. Here, the input voltage is fed to a rectifier, with output being supplied by an inverter. Under normal operating conditions, the inverter receives its supply directly from the rectifier, when the power supply fails it is supplied directly from the batteries. Consumers have no direct connection to mains AC power supply; the UPS protects them from all power grid problems. In critical situations and with sensitive equipment, protection by VFI technology is highly recommended.
UPS topologies - online / double-conversion UPS


  • Sinusoidal input current and output voltage
  • No switching times, therefore no gaps in coverage
  • Frequency converter operation possible
  • Additional internal redundancy switch over
  • Optimum protection against power disturbances



  • Lower efficiency in comparison to VI technology
  • More cost intensive comparison to VFD technology
Online UPS scheme


  • Protect C online UPS

    double-conversion (VFI)
    1 kVA2 kVA3 kVA

    parallel mode possible:
    6 kVA10 kVA
  • Protec C Rack mount UPS
    Rackmount UPS online / double-conversion (VFI)

    3000 VA
  • Protect D line-interactive UPS (double-conversion) Rackmount
    Rackmount UPS

    double-conversion (VFI)
    1000 VA1500 VA
    2000 VA3000 VA

    parallel mode possible:
    6000 VA10000 VA
  • Protect 1 online Tower UPS

    online / double-conversion (VFI)

    10 kVA
    15 kVA
    20 kVA
  • Fluxpower HE UPS system
    UPS system

    10 - 20 kVA
    Input: 3-phase
    Output: 3-phase

  • Fluxpower HPI UPS System
    UPS system

    60 - 300 kVA
    Input: 3-phase
    Output: 3-phase