Introduction
1
Description of the application
2
SINAMICS DCM
Commissioning
3
DC converter
Application - 12-pulse parallel
connection with decoupled
interphase transformer
Dimensioning example
4
Symbols
5
Literature
6
Application Manual
05/2017
A5E34871844AQ/RS-AA/001
Legal information
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Siemens AG
Division Process Industries and Drives
Postfach 48 48
90026 NÜRNBERG
GERMANY
A5E34871844AQ/RS-AA/001
Ⓟ 08/2017 Subject to change
Copyright © Siemens AG 2017.
All rights reserved
Table of contents
1
2
3
Introduction ............................................................................................................................................. 7
1.1
Important note ........................................................................................................................... 7
1.2
Preliminary remarks .................................................................................................................. 7
Description of the application .................................................................................................................. 9
2.1
Infeed transformer ...................................................................................................................11
2.2
Converters ..............................................................................................................................11
2.3
Interface transformer...............................................................................................................11
2.4
Current transformer.................................................................................................................12
2.5
Drive motor/load ......................................................................................................................12
2.6
Actual value sensing of the load voltage ................................................................................12
Commissioning ..................................................................................................................................... 13
3.1
Current control optimization ....................................................................................................13
3.2
Test .........................................................................................................................................13
4
Dimensioning example .......................................................................................................................... 15
5
Symbols ................................................................................................................................................ 17
6
Literature .............................................................................................................................................. 19
Application - 12-pulse parallel connection with decoupled interphase transformer
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5
Table of contents
Application - 12-pulse parallel connection with decoupled interphase transformer
6
Application Manual, 05/2017, A5E34871844AQ/RS-AA/001
Introduction
1.1
1
Important note
The application is provided are not binding and do not claim to be complete regarding
configuration, parameterization or any eventuality which may arise. The dimensioning
example does not represent a customer-specific solution and is only intended to provide
assistance with typical applications. The company operating the system is responsible for
the correct operation of the dimensioned systems.
SIEMENS reserves the right to make changes and revisions to this document at any time
without prior notice. If there are any differences between the suggestions made in this
document and other Siemens publications, such as catalogs, the contents of the other
document(s) take priority.
1.2
Preliminary remarks
The 12-pulse converter circuit with interphase transformer is suitable for applications where
solutions based on individual reactors are not feasible.
The interface transformer acts to compensate the current in the direction of the load; as a
consequence, when using an ideal interface transformer, the load current is hardly smoothed
at all.
Application - 12-pulse parallel connection with decoupled interphase transformer
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7
Introduction
1.2 Preliminary remarks
Application - 12-pulse parallel connection with decoupled interphase transformer
8
Application Manual, 05/2017, A5E34871844AQ/RS-AA/001
Description of the application
2
The basis for the application with interphase transformer should be taken from application
document "12-pulse applications 09/2015", Reference [1]. This defines the basic
interconnection and parameterization. When dimensioning the individual components, the
notes provided in this Chapter as well as in Chapter 4 (Page 15) should be observed.
Application - 12-pulse parallel connection with decoupled interphase transformer
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9
Description of the application
Figure 2-1
Overview of the armature circuit with relevant signals
Legend
Position
Element
1
Supply transformer (see Chapter 2.1)
2
Converter (see Chapter 2.2)
3
Converter (see Chapter 2.2)
4
Interphase transformer (see Chapter 2.3)
5
Current transformer (see Chapter 2.4).
6
Drive motor / load (see Chapter 2.5).
7
Setpoint channel
8
Parallel connection interface
9
Actual load voltage
10
Actual load current
11
Actual value sensing, load voltage
Application - 12-pulse parallel connection with decoupled interphase transformer
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Description of the application
2.1 Infeed transformer
2.1
Infeed transformer
● 3-winding transformer or a group comprising 2 transformers.
● Phase of the secondary voltage shifted through 30° el. - possible vector groups are
Dd0y11, Dd0y5, Yy0d11, Yy0d5.
● Identical nominal secondary voltages
● Short-circuit voltage, primary-secondary uK1-2 and uK1-3 should be at least 4 %. Not
complying with this requirement can be compensated by installing commutating reactors
between the transformer and the individual converters, according to the engineering
specifications [2]. The short-circuit voltage - taking into account the reactance of any
commutation reactors - should not exceed 12%, referred to the rated converter current.
● As far as possible, the same short-circuit voltage, primary-secondary for both secondary
sides, uK1-2 and uK1-3.
Deviations of up to 10% with reference to the particular values are permissible (e.g.
maximum deviation uK1-2 = 3.6 % and uK1-3 = 4.4 %).
● The minimum short-circuit voltage between secondary windings uK2-3 should be higher
than 10 %. A lower level of decoupling between the two systems could result in instability
in the current distribution between the two system halves.
2.2
Converters
These converters belong to the SINAMICS DCM series of devices. The application
document involves typical applications for the selected devices; essentially, all SINAMICS
DCM devices can be used.
2.3
Interface transformer
The interface transformer is implemented as single-phase transformer.
● Ratio 1:1
● Frequency = 600% line frequency (300Hz at 50Hz system, 360Hz at 60Hz system)
● The no-load current I0 should be 5-12% of the rated current. The value of the no-load
current is to be achieved using the air gap in the interphase transformer core.
● The primary/secondary voltage is the U1_N = U2_N - is 0.65 times the line to line voltage of
the secondary side of the infeed transformer.
● The rated thermal currents I1_N = I2_N of the windings correspond to half the DC output
current of the system.
● The nominal power rating of interphase transformer SN* is ≥ 0.12x the nominal power
rating of the current transformer.
● The short-circuit voltage uK of the interphase transformer should, as a minimum, be 10% when considered as a transformer. A higher short-circuit voltage results in better current
smoothing - and increases the line harmonics.
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Description of the application
2.4 Current transformer
In addition to increasing the no-load current, the air gap in the interphase transformer also
results in achieving a lower sensitivity of the interphase transformer with respect to
saturation effects when both converters are operating unbalanced. Reducing - or even
eliminating - the air gap in the interphase transformer core reduces the no-load current, and
therefore increases the effect of the interphase transformer when it comes to improving the
system line harmonics. However, it should be noted that reducing the airgap increases the
sensitivity of the interphase transformer regarding saturation. If the no-load current of the
interphase transformer is to lie below 10%, for each % (percentage point) below 10%, the
nominal power rating should be increased by a factor of 1.1.
The precise dimensioning of the short-circuit voltage uK (or leakage inductance) and the noload current (or magnetizing inductance) of the interphase transformer depends on the
specific application. In addition, additional data is required, for example load inductance,
permissible current ripple, control dynamic response required etc. The requirements relating
to permissible line harmonics (current and voltage harmonics) as well as the existing
harmonic line distortion of other possible loads should also be clearly specified.
Based on this data, a precise numerical transient simulation can be performed to determine
the dispersion parameters of the interphase transformer. If, as a result of the simulation,
leakage inductance variables (or short-circuit voltage uK) are obtained that cannot be
implemented in practice, then the system is not suitable for the use of an interphase
transformer. In this case, the better solution is to equip each converter with individual
reactors.
2.4
Current transformer
We recommend that a suitable current transformer is used at the output to sense the current
actual value. The current actual value should be connected to one of the analog inputs of the
CUD provided for the purpose, see FP6850, FP2085, FP2090 as well as parameters
p81852, p81853 (master and slave) according to the List Manual [3].
2.5
Drive motor/load
The criteria listed are applicable for motor and/or resistive-inductive loads - including a
counter voltage - with either no non linearity, or just a small amount of non linearity. A
precise numerical simulation of the system is required if the system is to be
designed/dimensioned for loads that are strongly non linear - or for capacitive loads.
2.6
Actual value sensing of the load voltage
Sensing the actual voltage using a suitable voltage transformer (PT) at the load is necessary
to achieve stability in operation, if the electromotoric voltage is parameterized as input
variable of the precontrol. The voltage actual value should be connected to AI2 of the CUD
(master and slave); the appropriate parameters must be assigned during the commissioning
phase. See List Manual [3], function diagram FP6902, p51854, p51855.
Application - 12-pulse parallel connection with decoupled interphase transformer
12
Application Manual, 05/2017, A5E34871844AQ/RS-AA/001
Commissioning
3
The system response depends on many parameters; it is not possible to draw up a
parameter set that is generally applicable. As a consequence, it is absolutely essential that
an experienced technician manually post-optimizes the current controller.
3.1
Current control optimization
The current controller must be optimized according to the document 12-pulse applications
09/2015 [1] Chapter 3.3.4.2.
3.2
Test
The notes and information provided in this document are recommendations. These are
based on experience, state-of-the-art technology and numerical simulation. It must be
carefully verified that dimensioning and parameterizing are correct. This must be performed
in test operation, at the latest during the commissioning phase.
Application - 12-pulse parallel connection with decoupled interphase transformer
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Commissioning
3.2 Test
Application - 12-pulse parallel connection with decoupled interphase transformer
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Dimensioning example
4
A motor with the following key data is involved:
● UN = 600 V
● IN = 4000 A
After assessing the drive dynamic performance, line harmonics and other parameters, a
decision was made to use a 12-pulse parallel circuit with the following data:
● U2N = 575 V
● 2x SINAMICS DCM converters, 4Q 575 V / 2800 A
The infeed transformer is selected with the following key data:
● Transformer nominal power rating:
SNT = U2N * 3*√2 / π * IN * 1.05 = 575 * 3*√2 / π * 4000 A * 1.05
SNT = 3.26 MVA
● U1 = according to the system supply point (point of connection)
● U2 = U3 = 575V
● Dd0y11 vector group
● uK1-2 = 5%
● uK1-3 = 5%
● uK2-3 = 15%
Application - 12-pulse parallel connection with decoupled interphase transformer
Application Manual, 05/2017, A5E34871844AQ/RS-AA/001
15
Dimensioning example
The interphase transformer is defined as transformer:
● fN = 300Hz (6 × 50 Hz)
● Interphase transformer nominal power rating:
SNIT = 0.12 * 3.26 MVA = 195.6 kVA
● U1 = 0.65 * 575V = 380V
● U2 = U1 = 380V
● I0 = 10% * 195.6 kVA/380 V = 51.5 A
● Thermal current of the winding I1 = 2000A
● Thermal current of the winding I2 = 2000A
● Short-circuit voltage of the interphase transformer
uK = 15%
This interphase transformer has an effective inductance per phase:
The inductance values listed above can be measured between connections 1-3 or 2-3
The interface transformer described in the example mainly compensates the current in the
direction of the load; as a consequence, when using this interphase transformer, the load
current is hardly smoothed at all.
Application - 12-pulse parallel connection with decoupled interphase transformer
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5
Symbols
Symbol
Explanation
U1N, U2N
Nominal primary/secondary voltage of the transformer
I1N, I2N
Nominal primary/secondary voltage of the transformer
I0
Transformer no-load current
uK1-2
Short-circuit voltage, secondary winding 2 with respect to the primary winding
uK1-3
Short-circuit voltage, secondary winding 3 with respect to the primary winding
uK2-3
Short-circuit voltage, secondary winding 2 with respect to secondary winding 3
uK
Short-circuit voltage of the interphase transformer
SNIT
Nominal power rating of the interphase transformer, for dimensioning the interphase transformer, the nominal power rating with nominal core induction is
considered.
U1, U2
Rated voltages of the interphase transformer windings
I1 , I2
Rated currents of the interphase transformer windings
SNT
Type rating of the converter transformer
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Symbols
Application - 12-pulse parallel connection with decoupled interphase transformer
18
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6
Literature
[1] Siemens AG; 12-pulse applications 09/2015; A5E34871844G
[2] Siemens AG; SINAMICS DCM, commutating reactors, operating instructions 2013;
A5E32621741A
[3] Siemens AG; SINAMICS DCM List Manual, 6RX1800-0ED00
[4] Schäfer,J: Rectifier Circuits: Theory and Design, John Wiley&Sons Inc. USA, 1965;
CatNo. 65-12703
Application - 12-pulse parallel connection with decoupled interphase transformer
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19
Literature
Application - 12-pulse parallel connection with decoupled interphase transformer
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Application Manual, 05/2017, A5E34871844AQ/RS-AA/001
Siemens AG
Division Process Industries and Drives
Postfach 48 48
90026 NUREMBERG
GERMANY
Subject to change
A5E34871844AQ
© Siemens AG 2017
DC Converters
SINAMICS DCM
www.industry.siemens.com/drives