Efficiency Of Sinamics Converters At Full Load And At Partial Load; Converter Efficiency At Full Load - Siemens SINAMICS G130 Engineering Manual

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Efficiency of SINAMICS converters at full load and at partial load

In many applications energy savings can be made by the use of variable-speed drives instead of conventional drive
solutions. Particularly at pump and fan drives with a quadratic load characteristic, variable-speed drives can achieve
considerable energy savings at partial load operation. This is because these drives have a good efficiency in a wide
speed range. In order to be able to quantify these savings, precise information about the efficiency of converter and
motor are required depending on the load and the speed of the drive. The following paragraphs will explain how the
efficiency of the SINAMICS converters G130, G150 and S150 can be determined at full and partial load.
Definition of the converter efficiency
The efficiency of a converter is defined as the ratio of the active electrical power delivered at the output P
active electrical power taken at the input P
the input P , is bigger than the active electrical power at the output P
In
the following general formula can be used for calculating the converter efficiency η:

Converter efficiency at full load

The determination of the converter efficiency at full load η
asynchronous motor, which is adpated to the rated data of the converter regarding rated voltage and rated current
and which operates at its rated point. In order to calculate the efficiency η
the output of the converter P
The active power at the output of the converter at full load is
The output voltage V
Out-100
modulation, almost equal to the supply voltage on the input side V
current I of the converter and the power factor cosφ
Rated
adapted to the rated voltage and the rated current of the converter and which is operated at its rated point. Thus, at
full load, the active power at the output of the converter is
The power losses of the converter at full load P
instructions (equipment manuals) for SINAMICS G130, G150 and S150 converters.
From the active power P
calculated as
With this formula, the efficiency at full load of SINAMICS G130, G150 and S150 converters can be individually
calculated, depending on the supply voltage and the power factor of the connected motor.
If one does the efficiency calculation for the given converters, taking a typical power factor of cosφ
basis (4-pole asynchronous motor in the power range between 100 kW and 1000 kW), the following typical converter
efficiencies at full load will be calculated:
•
SINAMICS G130 and G150 with pulse frequency according to factory settings: η
•
SINAMICS S150 with pulse frequency according to factory settings:
Fundamental Principles and System Description
. If it is taken into consideration that the active electrical power taken at
In
P
η
=
P
and the power losses of the converter P
Out-100
= ⋅
P 3 V
−
Out 100
of SINAMICS converters in vector control mode, is, when operating with pulse-edge
=
P 3
−
Out 100
L-100
and the power losses P
Out-100
P
η
= − =
Out 100
+
100
P P
− −
Out 100 L 100
due to the power losses P
Out
P
=
Out Out
.
+
P P
In Out L
is based on the operation of the converter on an
100
100
must be specified.
L
ϕ
⋅ ⋅
I cos
− −
Out 100 Out 100 Mot
. The output current I
Line
is the power factor of an asynchronous motor, which is
Mot
ϕ
⋅ ⋅ ⋅
V I cos
.
Line Rated Mot
can be found in the technical data of the catalogs or operating
, the efficiency of the converter at full load can be
L-100
⋅ ⋅ ⋅
3 V I
(
Line Rated
⋅ ⋅ ⋅
3 V I cos
Line Rated
SINAMICS Engineering Manual - May 2008
Engineering Information
of the converter,
L
at this rated point, the active power at
.
is the rated output
Out-100
ϕ
cos
)
Mot
.
ϕ
+
P
−
Mot L 100
Mot
= 97.7 % - 98.3 %.
100
η
= 96.0 % - 96.5 %.
100
© Siemens AG
to the
Out
(1)
= 0.88 as a
103/396