Transformers; Unit Transformers - Siemens SINAMICS G130 Engineering Manual

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Transformers

Unit transformers

Unit transformers supply only a single converter unit and are rated specifically for the power of the specific converter
unit.
If a converter is supplied by a unit transformer, a line reactor does not generally need to be installed provided that the
relative short circuit voltage u
Exceptions:
•
With S120 Smart Infeeds a line reactor is not required, only if the relative short circuit voltage u
transformer is ≥ 8%.
•
If converters with rectifiers connected in parallel are being used (high power output G150 with 2 power units
connected in parallel or S120 Basic Infeeds / S120 Smart Infeeds with power units connected in parallel),
line reactors are required to provide balanced current distribution in 6-pulse operation.
Calculation of apparent power S
The required rated apparent power S
P
> W
S k
T *
λ η η
* Converter *
Key to equation:
•
P
W
•
η
Converter
•
η
Motor
•
λ
•
kFactor which allows for transformer stray losses as a result of line-side harmonic currents
The line power factor λ is obtained as follows:
I
λ ϕ
( ) 1
= =
g cos
* 1 1
I
eff
Key to equation:
•
g
1
•
cos φ
1
For outputs of > approx. 50 kW, i.e. the lowest converter rating for which unit transformers can be used, the following
values are accurate approximations:
•
η ≈ 0.98
Converter
•
η ≈ 0.96
Converter
•
η
= 0.93 to 0.97
Motor
•
λ ≈ 0.95
•
λ = 1 or λ = cos φ
•
k = 1.20
•
k = 1.15
•
k = 1.10
•
k = 1
Fundamental Principles and System Description
of the transformer is ≥ 4%
k
of a unit transformer
T
can be calculated from the power balance of the drive:
T
Motor
Shaft output (continuous output) of the motor or rated output of the converter
Efficiency of converter
Efficiency of motor
Line power factor
ϕ
cos
* 1
Fundamental factor of current
Line-side power factor of fundamental current
For G130, G150 converters and units with S120 Basic Infeeds or S120 Smart
Infeeds
For S150 converters and units with S120 Active Infeeds
η ≈ 0.93 for motor output of 50 kW rising to η ≈ 0.97 for a motor output of 1MW
For G130, G150 converters and S120 Basic Infeeds and S120 Smart Infeeds
For S150 converters and converters with Active Infeed:
AI
λ = 1 if cos φ
= 1 is parameterized for the Active Infeed (factory setting),
AI
λ = cos φ if cos φ
AI
For systems configured with a standard distribution transformer and G130
without LHF, G150 without LHF, S120 Basic Infeeds and S120 Smart Infeeds
For systems configured with a standard distribution transformer and
G130 or G150 with Line Harmonics Filter LHF
For systems configured with a standard distribution transformer
and S150 and S120 Active Infeeds
When a converter transformer is used irrespective of the converter type
≠ 1 is parameterized for the Active Infeed
AI
SINAMICS Engineering Manual - May 2008
Engineering Information
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