Beckhoff SCT7 Series Operator's manual

Documentation | EN
SCT7xxx
Busbar split-core current transformers
2021-04-12 | Version: 1.2

Table of contents
SCT7xxx 3Version: 1.2
Table of contents
1 Foreword ....................................................................................................................................................5
1.1 Notes on the documentation..............................................................................................................5
1.2 Safety instructions .............................................................................................................................6
2 Product overview.......................................................................................................................................8
2.1 Introduction........................................................................................................................................8
2.2 Basics current transformers...............................................................................................................9
2.3 Product categories – SCTxxxx current transformer.........................................................................12
2.4 Notes on class accuracy SCT transformers ....................................................................................20
3 Technical data..........................................................................................................................................21
3.1 SCT71xx | Busbar split-core current transformers, size 1 ...............................................................21
3.1.1 SCT71xx | General .......................................................................................................... 21
3.1.2 SCT7105 | Busbar split-core current transformer for primary currents 0…100 A/0…200 A,
accuracy class 3, size 1................................................................................................... 23
3.1.3 SCT7115 | Busbar split-core current transformer for primary current 0...250 V / 0…400 A,
accuracy class 1, size 1................................................................................................... 24
3.1.4 SCT7125 | Busbar split-core current transformer for primary current 0…400 A, accuracy
class 0.5, size 1 ............................................................................................................... 25
3.2 SCT72xx | Busbar split-core current transformers, size 2 ...............................................................26
3.2.1 SCT72xx | General .......................................................................................................... 26
3.2.2 SCT7215 | Busbar split-core current transformer for primary currents 0…500/0…600 A,
accuracy class 1, size 2................................................................................................... 28
3.2.3 SCT7225 | Busbar split-core current transformer for primary currents 0…500/0…600 A,
accuracy class 0.5, size 2................................................................................................ 29
3.3 SCT73xx | Busbar split-core current transformers, size 3 ...............................................................30
3.3.1 SCT73xx | General .......................................................................................................... 30
3.3.2 SCT7315 | Busbar split-core current transformer for primary currents 0…750 to 0...1500
A, accuracy class 1, size 3 .............................................................................................. 32
3.3.3 SCT7325 | Busbar split-core current transformer for primary currents 0…750 to 0...1500
A, accuracy class 0.5, size 3 ........................................................................................... 33
3.4 SCT74xx | Busbar split-core current transformers, size 4 ...............................................................34
3.4.1 SCT74xx | General .......................................................................................................... 34
3.4.2 SCT7415 | Busbar split-core current transformer for primary currents 0…1500 to 0…5000
A, accuracy class 1, size 4 .............................................................................................. 36
3.4.3 SCT7425 | Busbar split-core current transformer for primary currents 0...1500 to 0...5000
A, accuracy class 0.5, size 4 ........................................................................................... 37
4 Commissioning........................................................................................................................................38
4.1 Installation .......................................................................................................................................38
4.2 Maintenance and inspection............................................................................................................41
4.3 Troubleshooting...............................................................................................................................42
5 Application example................................................................................................................................43
5.1 Power measurement at a machine..................................................................................................43
6 Appendix ..................................................................................................................................................45
6.1 Documentation issue status ............................................................................................................45
6.2 Support and Service ........................................................................................................................46

Table of contents
SCT7xxx4 Version: 1.2

Foreword
SCT7xxx 5Version: 1.2
1 Foreword
1.1 Notes on the documentation
Copyright
© Beckhoff Automation GmbH & Co. KG, Germany.
The reproduction, distribution and utilization of this document as well as the communication of its contents to
others without express authorization are prohibited.
Offenders will be held liable for the payment of damages. All rights reserved in the event of the grant of a
patent, utility model or design.
Disclaimer
The documentation has been prepared with care. The products described are, however, constantly under
development.
We reserve the right to revise and change the documentation at any time and without prior announcement.
No claims for the modification of products that have already been supplied may be made on the basis of the
data, diagrams and descriptions in this documentation.
EtherCAT® is registered trademark and patented technology, licensed by Beckhoff Automation GmbH,
Germany.
Trademarks
Beckhoff®, TwinCAT®, EtherCAT®, EtherCATG®, EtherCATG10®, EtherCATP®, SafetyoverEtherCAT®,
TwinSAFE®, XFC®, XTS® and XPlanar® are registered trademarks of and licensed by Beckhoff Automation
GmbH. Other designations used in this publication may be trademarks whose use by third parties for their
own purposes could violate the rights of the owners.
Patent Pending
The EtherCAT Technology is covered, including but not limited to the following patent applications and
patents: EP1590927, EP1789857, EP1456722, EP2137893, DE102015105702 with corresponding
applications or registrations in various other countries.
Intended audience
This description is only intended for the use of trained specialists in control and automation engineering who
are familiar with the applicable national standards.
It is essential that the documentation and the following notes and explanations are followed when installing
and commissioning these components.
It is the duty of the technical personnel to use the documentation published at the respective time of each
installation and commissioning.
The responsible staff must ensure that the application or use of the products described satisfy all the
requirements for safety, including all the relevant laws, regulations, guidelines and standards.

Foreword
SCT7xxx6 Version: 1.2
1.2 Safety instructions
Description of instructions
In this documentation the following instructions are used.
These instructions must be read carefully and followed without fail!
DANGER
Serious risk of injury!
Failure to follow this safety instruction directly endangers the life and health of persons.
WARNING
Risk of injury!
Failure to follow this safety instruction endangers the life and health of persons.
CAUTION
Personal injuries!
Failure to follow this safety instruction can lead to injuries to persons.
NOTE
Damage to environment/equipment or data loss
Failure to follow this instruction can lead to environmental damage, equipment damage or data loss.
Tip or pointer
This symbol indicates information that contributes to better understanding.
Exclusion of liability
All the components are supplied in particular hardware and software configurations appropriate for the
application. Modifications to hardware or software configurations other than those described in the
documentation are not permitted, and nullify the liability of Beckhoff Automation GmbH & Co. KG.
Personnel qualification
This description is only intended for trained specialists in control, automation and drive engineering who are
familiar with the applicable national standards.
Intended use
If the equipment is used in a manner not specified by the manufacturer, the protection provided by the
equipment may be impaired
Safety regulations
Please note the following safety instructions and explanations!
Product-specific safety instructions can be found on following pages or in the areas mounting, wiring,
commissioning etc.
Current transformer safety instructions
The following points must be noted:
• The applicable laws, standards and regulations.
• The state of the art at the time of installation.
• The technical rules.

Foreword
SCT7xxx 7Version: 1.2
• The operating instructions.
• The fact that operating instructions can only list general regulations and that these regulations must be
followed.
• Check the device carefully for transport damage prior to commissioning. The device must not be put
into operation if it is mechanically damaged.
• The devices described are intended for installation by qualified electricians and may only be installed in
electrical plant rooms or in closed housings. Any other use or the disregard of these application notes
will result in the loss of the warranty/guarantee.
• The devices may only be installed in dry indoor rooms.
• Do not mount on highly flammable materials.
• Operation with a higher current than the rated current specified on the name plate can lead to
overheating of the current transformer and thus to burns.

Product overview
SCT7xxx8 Version: 1.2
2 Product overview
2.1 Introduction
SCTxxxx | Current transformers (CT) for energy measurement
Fig.1: SCT current transformers
With its SCT current transformers, Beckhoff makes it possible to implement reliable power sensor technology
in the field, which is directly integrated into the PC-based control system. Users can select from two device
concepts, each with various designs and performance categories that are highly scalable and therefore
suitable for any application. The SCT portfolio is extremely broad-based, ranging from low-cost 3-phase CT
sets for building technology to standard industrial transformers for machines through to solutions for
inspection and test stands with extra-high accuracy requirements.
The choice of the suitable product category [}12] depends on the type of use. While ring-type CTs are
predestined for cost-effective and accurate data acquisition in new installations, split-core CTs provide the
ideal solution for retrofit solutions due to their easy installation.

Product overview
SCT7xxx 9Version: 1.2
2.2 Basics current transformers
Function and design
A current transformer is a transforming device that transforms an input current into a processable current
signal at the output. A current transformer is mainly used to transform currents of large magnitudes to directly
measurable, smaller values in the milliampere or small ampere range. With a classic current transformer, the
input current is proportional to the output current. Due to the physical principle and the mechanical
construction, the current signal is transmitted galvanically isolated to the evaluation electronics.
A current transformer basically consists of a small number of windings on the primary side and a larger
number of windings on the secondary side. The current to be converted flows through the primary side. The
windings are usually wound on an alternating magnetic ferrite ring core.
A typical transformer type is the ring core or ring-type current transformer. The current rail or current-carrying
cable is often used as the primary winding, which is guided through the toroidal core of the transformer.
Thus, the rail or line forms the primary winding with one turn. The secondary winding is located on the ring
core. The transformation is determined by the ratio of the number of primary and secondary windings. The
classic structure of a ring-type current transformer is shown in the following figure.
Fig.2: Principle ring-type current transformer
Another classic type is the coiled current transformer. In this type of transformer, the primary winding is a
current-carrying wire which is wound around the ring core on the primary side. In this case, the primary
winding number is >1, but smaller than the secondary winding number. The principle is shown in the
following figure
Fig.3: Principle coil current transformer

Product overview
SCT7xxx10 Version: 1.2
WARNING
Dangerous voltages with secondary side not connected
The secondary winding must be connected to a current measuring device or short-circuited, otherwise high
core losses or dangerous voltages may occur on the secondary side. Before replacing the measuring elec-
tronics in the secondary circuit, the current transformer must therefore be short-circuited at its secondary
terminals.
Grounding of secondary terminals
According to DIN VDE 0141 (01/2000) paragraph 5.3.4, current and voltage transformers for nomi-
nal voltages from Um = 3.6 kV must be grounded on the secondary side. For low voltages (Um ≤
1.2 kV), grounding is not required if the transformer housings do not have any metal surfaces with
large contact areas.
Characteristic values and calculation
In principle, the construction, and thus also the calculation, correspond to a normal transformer. The basic
relationship between input and output current is determined by the ratio of the number of turns N of the
primary and secondary sides. An important characteristic value in the design of a current transformer is
therefore the transformer ratio.
IOut = N1/N2 * IIn

Product overview
SCT7xxx 11Version: 1.2
Technical terms of current transformers
Term Explanation
Primary rated current Ipr
(alternative formula symbol IN)
Value of the rated current on the primary side.
Secondary rated current Isr Value of the rated current on the secondary side.
Rated power SrValue of apparent power (in [VA]) that the transformer can deliver
to the secondary circuit at secondary rated current and rated load.
Rated frequency fRValue of the rated frequency.
Accuracy class Indication that the measurement deviations are within specified
limits under prescribed application conditions.
Rated insulation level UmMaximum voltage; RMS value of the highest conductor-to-
conductor voltage for which a instrument transformer is rated with
respect to its insulation.
Specified is the value of the rated insulation level in three values:
1. maximum value of the conductor-to-conductor voltage for which
the isolation of the transducers is rated;
2. value of the rated AC voltage (50 Hz, 1 min) with which the
insulation safety of the equipment is tested
3. value of the surge voltage level (this specification is mostly
unoccupied here, since IEC 61869/1 only requires a specification
for transformers with a conductor-to-conductor voltage of >1.2 kV)
Overcurrent limiting factor (FS) Ratio of the rated limiting current to the primary rated current.
Thermal rated continuous current Icth Value of the continuous current in the primary winding at which the
overtemperature does not exceed the value specified in the
standard, with the secondary winding loaded with the rated load.
Rated short-time thermal current Ith Value of short-time current for a limited time in the primary winding
at which the excess temperature does not exceed the value
specified in the standard, with the secondary winding loaded with
the rated load.
Rated impulse current Idyn Maximum value of the primary current, the electromagnetic force
effect of which does not cause any electrical and mechanical
damage to the current transformer with short-circuited secondary
winding.
“Open voltage" of
current transformers
Current transformers which are not directly connected to a load
must be short-circuited on the secondary side for safety reasons!
A current transformer operated open on the secondary side induces
very high peak voltage values at its secondary terminals. The
magnitudes of these voltages can reach values of up to several
kilovolts, depending on the dimensioning of the current transformer,
and thus represent a danger to persons and the functional safety of
the transformer. For safety reasons, and to avoid magnetization of
the core iron during secondary-side open operation, open operation
should generally be avoided.
Grounding of secondary terminals According to DIN VDE 0141 (01/2000) paragraph 5.3.4, current and
voltage transformers for nominal voltages from Um = 3.6 kV must
be grounded on the secondary side. For low voltages (Um ≤ 1.2
kV), grounding is not required if the transformer housings do not
have any metal surfaces with large contact areas.

Product overview
SCT7xxx12 Version: 1.2
2.3 Product categories – SCTxxxx current transformer
Breakdown of the type designation of the SCT current transformer
Fig.4: Designation key of the SCT current transformers

Product overview
SCT7xxx 13Version: 1.2
Coil current transformers
Fig.5: SCT0xxx
In order to guarantee the power transmission, current transformers need a correspondingly large measuring
core volume with decreasing primary rated currents. The dimensions of standard current transformers would
quickly hit their limits on the basis of this physical principle. The SCT0xxx coil current transformers with
electrical isolation are specially designed for these low primary rated currents and are used in corresponding
applications.
Coil current transformers
SCT0111 Accuracy class 1,
primary current 0…1 A AC to 0…30 A AC,
secondary current 1 A AC
SCT0121 Accuracy class 0.5,
primary current 0…1 A AC to 0…30 A AC,
secondary current 1 A AC

Product overview
SCT7xxx14 Version: 1.2
Mini ring-type current transformer
Fig.6: SCT1xxx
The SCT1111 mini ring-type current transformer can be positioned on a DIN rail by means of snap-on
fastening and is thus suitable for measurements in very tight installation spaces, e.g. directly in the sub-
distribution unit. Two current transformers are attached to the DIN rail, while the third current transformer in
plugged into the fastened current transformers.
The connection is realized via removable picoMAX® connectors, which enables pre-wiring.
Mini ring-type current transformer
SCT1111 Accuracy class 1,
primary current 0…32 A AC to 0…64 A AC,
secondary current 1 A AC,
max. diameter round conductor 7.6 mm (size 1)

Product overview
SCT7xxx 15Version: 1.2
Ring-type current transformer
Fig.7: SCT2xxx
The SCT2xxx series offers a large selection of ring-type current transformers for primary currents from 60 to
2500 A in six sizes and two accuracy classes. The innovative screwless connection technology for rigid and
flexible conductors saves time – ferrules can be dispensed with here.

Product overview
SCT7xxx16 Version: 1.2
Ring-type current transformer
SCT2111 Accuracy class 1,
primary current 0…60 A AC to 0…500 A AC,
secondary current 1 A AC,
max. diameter round conductor 25.7 mm (size 1)
SCT2121 Accuracy class 0.5,
primary current 0…125 A AC to 0…600 A AC,
secondary current 1 A AC,
max. diameter round conductor 25.7 mm (size 1)
SCT2211 Accuracy class 1,
primary current 0…600 A AC / 0…750 A AC,
secondary current 1 A AC,
max. diameter round conductor 31.8 mm (size 2)
SCT2221 Accuracy class 0.5,
primary current 0…600 A AC / 0…750 A AC,
secondary current 1 A AC,
max. diameter round conductor 31.8 mm (size 2)
SCT2311 Accuracy class 1,
primary current 0…800 A AC / 0…1000 A AC,
secondary current 1 A AC,
max. diameter round conductor 43.7 mm (size 3)
SCT2321 Accuracy class 0.5,
primary current 0…800 A AC / 1000 A AC,
secondary current 1 A AC,
max. diameter round conductor 43.7 mm (size 3)
SCT2411 Accuracy class 1,
primary current 0…1250 A AC / 0…1500 A AC,
secondary current 1 A AC,
max. diameter round conductor 43.7 mm (size 4)
SCT2421 Accuracy class 0.5,
primary current 0…1250 A AC / 0…1500 A AC,
secondary current 1 A AC,
max. diameter round conductor 43.7 mm (size 4)
SCT2515 Accuracy class 1,
primary current 0…2000 A AC,
secondary current 5 A AC,
max. diameter round conductor 54.7 mm (size 5)
SCT2525 Accuracy class 0.5,
primary current 0…2000 A AC,
secondary current 5 A AC,
max. diameter round conductor 54.7 mm (size 5)
SCT2615 Accuracy class 1,
primary current 0…2500 A AC,
secondary current 5 A AC,
max. diameter round conductor 70 mm (size 6)
SCT2625 Accuracy class 0.5,
primary current 0…2500 A AC,
secondary current 5 A AC,
max. diameter round conductor 70 mm (size 6)

Product overview
SCT7xxx 17Version: 1.2
3-phase ring-type current transformers
Fig.8: SCT3xxx
The compact SCT3xxx 3-phase ring-type current transformers for direct mounting under commonly used
power switches measure primary currents from 3 x 50 to 3 x 600 A, with secondary currents of 1 or 5 A. The
whole of the SCT3xxx series is available in accuracy class 1 and is supplemented by the SCT3121-0125 and
SCT3121-0150 current transformers in accuracy class 0.5.
3-phase ring-type current transformers
SCT3111 Accuracy class 1,
primary current 3 x 0…50 A AC to 3 x 0…150 A AC,
secondary current 1 A AC,
max. diameter round conductor 13.5 mm (size 1)
SCT3121 Accuracy class 0.5,
primary current 3 x 0…125 A AC / 3 x 0…150 A AC,
secondary current 1 A AC,
max. diameter round conductor 13.5 mm (size 1)
SCT3215 Accuracy class 1,
primary current 3 x 0…100 A AC to 3 x 0…250 A AC,
secondary current 5 A AC,
max. diameter round conductor 18 mm (size 2)
SCT3315 Accuracy class 1,
primary current 3 x 0…250 A AC to 3 x 0…600 A AC,
secondary current 5 A AC,
max. diameter round conductor 22 mm (size 3)

Product overview
SCT7xxx18 Version: 1.2
Split-core current transformers
Fig.9: SCT6xxx
The separable measuring system of the SCT6xxx split-core current transformers enables flexible retrofitting
without disconnecting the primary conductor. Due to the minimal installation effort, they are suitable for use
in places that are difficult to access or where space is limited. Four sizes are available. Accuracy class 3 is
suitable for primary currents from 60 to 150A, accuracy class 1 for 200 to 1000A.
Split-core current transformers
SCT6101 Accuracy class 3,
primary current 0…60 A AC to 0…150 A AC,
secondary current 1 A AC,
max. diameter round conductor 18.5 mm (size 1)
SCT6311 Accuracy class 1,
primary current 0…200 A AC / 0…250 A AC,
secondary current 1 A AC,
max. diameter round conductor 18.5 mm (size 3)
SCT6321 Accuracy class 0.5,
primary current 0…200 A AC / 0…250 A AC,
secondary current 1 A AC,
max. diameter round conductor 18.5 mm (size 3)
SCT6411 Accuracy class 1,
primary current 0…300 A AC to 0…500 A AC,
secondary current 1 A AC,
max. diameter round conductor 27.9 mm (size 4)
SCT6421 Accuracy class 0.5,
primary current 0…400 A AC / 0…500 A AC,
secondary current 1 A AC,
max. diameter round conductor 27.9 mm (size 4)
SCT6615 Accuracy class 1,
primary current 0…600 A AC / 0…750 A AC,
secondary current 5 A AC,
max. diameter round conductor 42.4 mm (size 6)
SCT6625 Accuracy class 0.5,
primary current 0…600 A AC / 0…750 A AC,
secondary current 5 A AC,
max. diameter round conductor 42.4 mm (size 6)
SCT6715 Accuracy class 1,
primary current 0…800 A AC / 0…1000 A AC,
secondary current 5 A AC,
max. diameter round conductor 2 x 42.4 mm (size 7)
SCT6725 Accuracy class 0.5,
primary current 0…800 A AC / 0…1000 A AC,
secondary current 5 A AC,
max. diameter round conductor 2 x 42.4 mm (size 7)

Product overview
SCT7xxx 19Version: 1.2
Busbar split-core current transformers
Fig.10: SCT71xx
Like the SCT6xxx series, the SCT7xxx busbar split-core current transformers for primary currents up to
5000A can be retrofitted to existing systems with no great mounting effort. From 500A, there is a choice
between accuracy class 0.5 and 1 for each primary current. The SCT7105-0100 and SCT7105-200 current
transformers support accuracy class 3.
Busbar split-core current transformers
SCT7105 Accuracy class 3,
primary current 0…100 A AC / 0…200 A AC,
secondary current 5 A AC,
max. diameter round conductor 20 mm (size 1)
SCT7115 Accuracy class 1,
primary current 0…200 A AC / 450 A AC,
secondary current 5 A AC,
max. diameter round conductor 20 mm (size 1)
SCT7125 Accuracy class 0.5,
primary current 0…400 A AC,
secondary current 5 A AC,
max. diameter round conductor 20 mm (size 1)
SCT7215 Accuracy class 1,
primary current 0…500 A AC / 0…600 A AC,
secondary current 5 A AC,
max. diameter round conductor 50 mm (size 2)
SCT7225 Accuracy class 0.5,
primary current 0…500 A AC / 0…600 A AC,
secondary current 5 A AC,
max. diameter round conductor 50 mm (size 2)
SCT7315 Accuracy class 1,
primary current 0…750 A AC to 0…1500 A AC,
secondary current 5 A AC,
max. diameter round conductor 80 mm (size 3)
SCT7325 Accuracy class 0.5,
primary current 0…750 A AC to 0…1500 A AC,
secondary current 5 A AC,
max. diameter round conductor 80 mm (size 3)
SCT7415 Accuracy class 1,
primary current 0…1500 A AC to 0…5000 A AC,
secondary current 5 A AC,
max. diameter round conductor 80 mm (size 4)
SCT7425 Accuracy class 0.5,
primary current 0…1500 A AC to 0…5000 A AC,
secondary current 5 A AC,
max. diameter round conductor 80 mm (size 4)

Product overview
SCT7xxx20 Version: 1.2
2.4 Notes on class accuracy SCT transformers
Current transformers are divided into classes according to their accuracy. The Beckhoff SCT current
transformers are available in the standard accuracy classes 0.5; 1 and 3, depending on the product
category. The class designation corresponds to an error curve with regard to current amplitude and angular
error. Beckhoff SCT current transformers conform to the IEC 61869 standard.
The accuracy classes of current transformers are related to the rated current. If current transformers are
operated with a current that is low in relation to the rated current, the measuring accuracy decreases. The
following tables show the fault limit values taking into account the rated current values:
Class accuracy Current error (±) in % at % of rated current
5 % 20 % 50 % 100 % 120 %
0,5 1,5 % 0,75 % - 0,5 % 0,5 %
13,0 % 1,5 % - 1,0 % 1,0 %
3- - 3 % - 3 %
Class accuracy Phase shift/error angle (±) at % of rated current
Angular minutes [ ´ ] Radians [rad]
5 % 20 % 50 % 100 % 120 % 5 % 20 % 50 % 100 % 120 %
0,5 90‘ 45‘ - 30‘ 30‘ 2,7 rad 1,35 rad - 0,9 rad 0,9 rad
1180‘ 90‘ - 60‘ 60‘ 5,4 rad 2,7 rad - 1,8 rad 1,8 rad
3- - - - - - - - - -
Fig.11: Characteristic curves accuracy classes/primary current
Adjusting the transducer rating
In order to use the optimum accuracy of the transducer, you must ensure a suitable transducer rat-
ing in your application through the wiring between the transducer and the measuring terminal. This
is done by using 0.25 to 1.0 times the rated power of the transducer.
Additional resistors in the secondary path can be used to match the transducer and measuring ter-
minal to each other.