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UPS classification based on operating behaviour

in accordance with EN 50091-3, IEC 62040-3:1999 and VDE 0558 Part 530

The aim of classifying UPS devices according to their operating behaviour is to provide a common basis for assessing all manufacturer data. This enables users to compare products from different manufacturers with similar performance ratings from the same point of view.

Classification code


VFI- SS- 111
The first group of letters describes the
Influence of the output by input
The second group of letters describes the
waveform of the output voltage
The third block of digits describes the behaviour of the
output in the event of load jumps and changes to the operating mode
Only for normal operation 1st letter: Normal operation or bypass
2nd letter: battery operation
1st digit: when changing the operating mode
2nd digit: for linear
load jump (worst case)
3rd digit: for non-linear
load jump (worst case)

Code meaning

Code meaning

Code meaning
VFI (Voltage and Frequency Independent) UPS output independent of the mains; voltage and frequency changes within the limits of IEC 61000-2-2

VI ( Voltage Independent) UPS output dependent on the mains frequency; voltage stabilised (electrical/passive) within the limits for normal operation

VFD (Voltage and Frequency Dependent) UPS output dependent on voltage and frequency changes in the mains.

S: Waveform of the output voltage sinusoidal distortion shape D < 0.08 harmonic < IEC 61000-2-2 with linear and non-linear reference load

X: Waveform of the output voltage sinusoidal with non-linear load. With non-linear load, distortion factor D-0.08 for overload.

Y: Non-sinusoidal voltage curve exceeds the limit values according to IEC 61000-2-2

1: uninterruptible

2: voltage interruption
3: Voltage interruption
< 10 ms
4: Ask the manufacturer for properties

The first three letters indicate the quality of supply of the consumer load during normal operation, which is expected for more than 90% of the operating time. The selection is determined by whether narrow further tolerances are permissible because the given load is insensitive to changes in frequency or voltage. The following two letters indicate the voltage waveform in normal operation (including occasional bypass operation) and in battery operation.

The connection of larger non-linear loads can cause a distortion of the voltage curve compared to that of a resistive or inductive load.

If the waveform is sinusoidal for a linear load, the necessary restrictions for non-linear loads are specified by the manufacturer and indicated by an ‘X’.

UPS devices that generate a non-sinusoidal voltage (e.g. rectangular or stepped) are labelled ‘Y’. This type of waveform is permissible for many loads temporarily or in continuous operation.

The last three digits indicate the transient voltage behaviour of the UPS devices under different conditions and indicate the most unfavourable condition. These characteristics are determined with standardised loads. The actual behaviour for a given application should be clarified with the manufacturer.

Assignment of our UPS series

UPS classification according to
EN 50091-3 and EN 62040-3
Common designation ERREPI products
VFI (Voltage and Frequency Independent)

(Input voltage and input frequency independent)

double conversion
Continuous operation
Continuous converter
double conversion
  • Series 03 (OP1003 - OP10003)
  • Series OP-RT
  • Series 03 Rack (OP1003R - OP100003R)
  • TRIMOD 1/3 U
  • TMP
  • TTP
  • GM 1PRO
  • GM 3PRO
VI (Voltage Independent)

(input voltage independent)

Delta conversion
Single conversion
Active tracking mode
  • NetPower NP-M series
  • Series NetPower NP-RT
  • Series CPN
  • RPT series
VFD (Voltage and Frequency Dependent)

(Input voltage and input frequency dependent)

Passive tracking mode
Standby mode
  • WOW series