Siemens SIMARIS User Manual
Totally Integrated Power
Technical Series
Edition 3
Modeling of systems for Uninterruptible Power Supply (UPS) in SIMARIS®
design for application in data centers
siemens.com/tip-cs
Technical Series Edition 3
Technical Series Edition 3
Modeling of systems for Uninterruptible Power Supply (UPS) in
SIMARIS® design for application in data centers
1. Basics
Uninterruptible power supply to the servers is of fundamental importance for data centers in order to have those
available 24hours a day and 365days a year. To achieve
this goal, the power supply must be thoroughly planned.
This includes the coordination between the components to
be used, taking into account that the selection and integration of UPS systems in the power supply concept is
essential in this process.
Meaning of the code elements:
AAA
The characteristic value describes the dependency of the UPS output supply in normal operation in case of change of voltage and fre-
quency at the input AC supply.
"VFD" (Voltage and Frequency Dependent):
UPS systems with VFD classification must pro-
tect the load against power failure.
In this case, the UPS output is influenced by
changes of the input AC voltage and the frequency, and it is not suitable for assuming
additional correction functions which may
arise from the application of an
autotransformer.
Characteristic values dependent on the voltage curve. A difference is made between
the following operating modes:
• Normal or bypass operation (first character)
• Energy storage operation (second character)
"S": The voltage curve is sinusoidal.
In case of linear and non-linear reference load (the exact specification can be found
in IEC62040-3), the total harmonic distortion is lower than 8%. The curve shape is
defined as sinusoidal.
"X": The curve shape is only sinusoidal in case of linear load. In case of non-linear refe-
rence load, the curve shape is no longer sinusoidal, as the total harmonic distortion
exceeds the limit value of 8%.
"Y": The voltage curve is not sinusoidal, neither for linear nor for non-linear reference
loads. The limit value of 8% is exceeded in both cases.
In accordance with the IEC 62040-3 standard
(DINEN62040-3; VDE0558 Part 530), UPS manufacturers
can designate their devices according to the classification
described therein. The assessment criteria are shown
hereafter as an excerpt:
Designation code: AAA BB CCC
i
e.g.: VFI SS 111 (highest classification)
BB
"VI" (Voltage Independent):
Like UPS systems with VFD, UPS systems with
VI classification must protect the load against
power failure, and also additionally ensure the
supply in case of
• undervoltage permanently applied to the
input
• overvoltage permanently applied to the
input.
The output of a UPS with VI classification
depends on the frequency of the AC voltage
input, and the output voltage must remain
within the prescribed limit voltage values.
"VFI" (Voltage and Frequency Dependent):
UPS systems with VFI classification are independent of (mains) supply voltage and frequency fluctuations, and must protect the load
against negative effects of such fluctuations
without discharging the energy storage
system.
CCC
Characteristic values for the dynamic behavior of the UPS output voltage:
• First numeral: in case of change of the operating mode
• Second numeral: in case of linear load step in normal or battery operation
(specification for the worst case)
• Third numeral: in case of non-linear load step in normal or battery operation
(specification for the worst case)
"1": required operating behavior for sensitive, critical loads.
The UPS output voltage remains within the limit values of curve 1 (see IEC62040-3)
in this section.
"2": permissible operating behavior for most of the critical loads.
The UPS output voltage remains within the limit values of curve 2 (see IEC62040-3)
in this section.
"3": permissible operating behavior for most of the general IT loads, e.g. switched-mode
power supplies.
The UPS output voltage remains within the limit values of curve 3 (see IEC62040-3)
in this section.
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Technical Series Edition 3
With SIMARIS design, electrical networks can be dimensioned with minimum input effort on the basis of real
products – from the medium-voltage level down to the
power consumer (which in the case of a data center means
down to the rack where the ICT equipment (ICT: Information and Communication Technology) is supplied with
power). This reduces your efforts for the overall planning
of the power distribution a lot, and thus the time for
selecting and dimensioning the electrical equipment –
with a high level of planning security.
When UPS systems are integrated for planning the power
distribution, the functionality is structured in SIMARIS
design, both
• as a load for selecting the components of the infeed
(transformers, generators, cables, busbars, switching
devices)
• and as a power source to depict the effects on the
downstream network regarding the maximum short-circuit currents in case of transformer infeed, as well as the
minimum short-circuit currents in case of inverter opera-
tion mode.
Following the standard EN 50600-2-2, Clause 6.3.2, the
functional elements of a power distribution system must
be selected in accordance with the selectivity and shortcircuit withstand strength requirements in all operating
modes and during different operating phases.
To supply the connected loads, the
• supply via the UPS
• supply via a UPS bypass
must be considered. Infeed takes places either through a
supply network (e.g. primary infeed for VFI operation and
secondary supply in case of internal bypass operation of
the UPS), or through an additional supply (e.g. generator).
With SIMARIS design it is possible to verify – for the downstream network – the compliance with the electrotechnical
conditions according to the standard, such as the switch-
off condition according to IEC60364-4-41 (DINVDE0100
Part410), as well as the selectivity.
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