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SCT2
User Manual
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Beckhoff SCT2 User Manual

Documentation | EN
SCT2xxx
Ring-type current transformer
2021-04-12 | Version: 1.3

Table of contents

Table of contents
1 Foreword ....................................................................................................................................................5
2 Product overview.......................................................................................................................................8
2.3 Product categories – SCTxxxx current transformer.........................................................................12
2.4 Notes on class accuracy SCT transformers ....................................................................................20
3 Technical data..........................................................................................................................................21
3.1 SCT21xx | Ring-type current transformer, size 1.............................................................................21
3.1.1 SCT21xx | General .......................................................................................................... 21
3.1.2 SCT2111 | Ring-type current transformer for primary currents 0...60 A to 0...500 A, accu-
racy class 1, size 1 .......................................................................................................... 23
3.1.3 SCT2121 | Ring-type current transformer for primary currents 0…125 A to 0…600 A, ac-
curacy class 0.5, size 1.................................................................................................... 24
3.2 SCT22xx | Ring-type current transformer, size 2.............................................................................25
3.2.1 SCT22xx | General .......................................................................................................... 25
3.2.2 SCT2211 | Ring-type current transformer for primary currents 0...600 A/0...750 A, accu-
racy class 1, size 2 .......................................................................................................... 27
3.2.3 SCT2221 | Ring-type current transformer for primary currents 0…600 A/0…750 A, accu-
racy class 0.5, size 2 ....................................................................................................... 28
3.3 SCT23xx | Ring-type current transformer, size 3.............................................................................29
3.3.1 SCT23xx | General .......................................................................................................... 29
3.3.2 SCT2311 | Ring-type current transformer for primary currents 0…800 A/0…1000 A, accu-
racy class 1, size 3 .......................................................................................................... 31
3.3.3 SCT2321 | Ring-type current transformer for primary currents 0…800 A/0…1000 A, accu-
racy class 0.5, size 3 ....................................................................................................... 32
3.4 SCT24xx | Ring-type current transformer, size 4.............................................................................33
3.4.1 SCT24xx | General .......................................................................................................... 33
3.4.2 SCT2411 | Ring-type current transformer for primary currents 0…1250 A/0…1500 A, ac-
curacy class 1, size 4....................................................................................................... 35
3.4.3 SCT2421 | Ring-type current transformer for primary currents 0…1250 A/0…1500 A, ac-
curacy class 0.5, size 4.................................................................................................... 36
3.5 SCT25xx | Ring-type current transformer, size 5.............................................................................37
3.5.1 SCT25xx | General .......................................................................................................... 37
3.5.2 SCT2515 | Ring-type current transformers for primary current 0…2000 A, accuracy class
1, size 5 ........................................................................................................................... 39
3.5.3 SCT2525 | Ring-type current transformers for primary current 0…2000 A, accuracy class
0.5, size 5 ........................................................................................................................ 40
3.6 SCT26xx | Ring-type current transformer, size 6.............................................................................41
3.6.1 SCT26xx | General .......................................................................................................... 41
3.6.2 SCT2615 | Ring-type current transformers for primary current 0…2500 A, accuracy class
1, size 6 ........................................................................................................................... 43
3.6.3 SCT2625 | Ring-type current transformers for primary current 0...2500 A, accuracy class
0.5, size 6 ........................................................................................................................ 44
4 Commissioning........................................................................................................................................45
SCT2xxx 3Version: 1.3
Table of contents
5 Application example................................................................................................................................50
5.1 Power measurement at a machine..................................................................................................50
6 Appendix ..................................................................................................................................................52
6.1 Documentation issue status ............................................................................................................52
6.2 UL notes ..........................................................................................................................................53
6.3 Support and Service ........................................................................................................................54
SCT2xxx4 Version: 1.3
Foreword

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.
SCT2xxx 5Version: 1.3
Foreword

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.
SCT2xxx6 Version: 1.3
Foreword
• 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.
SCT2xxx 7Version: 1.3
Product overview

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.
SCT2xxx8 Version: 1.3
Product overview

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
SCT2xxx 9Version: 1.3
Product overview
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 elec­tronics 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 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.
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.
I
= N1/N2 * I
Out
In
SCT2xxx10 Version: 1.3
Product overview
Technical terms of current transformers
Term Explanation
Primary rated current Ipr
Value of the rated current on the primary side.
(alternative formula symbol IN)
Secondary rated current I
Rated power S
r
sr
Value of the rated current on the secondary side. Value of apparent power (in [VA]) that the transformer can deliver
to the secondary circuit at secondary rated current and rated load.
Rated frequency f
R
Value of the rated frequency.
Accuracy class Indication that the measurement deviations are within specified
limits under prescribed application conditions.
Rated insulation level U
m
Maximum voltage; RMS value of the highest conductor-to­conductor 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 I
Value of the continuous current in the primary winding at which the
cth
overtemperature does not exceed the value specified in the standard, with the secondary winding loaded with the rated load.
Rated short-time thermal current IthValue 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 I
dyn
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.
SCT2xxx 11Version: 1.3
Product overview

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
SCT2xxx12 Version: 1.3
Product overview
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,
SCT0121 Accuracy class 0.5,
primary current 0…1 A AC to 0…30 A AC, secondary current 1 A AC
primary current 0…1 A AC to 0…30 A AC, secondary current 1 A AC
SCT2xxx 13Version: 1.3
Product overview
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 sub­distribution 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)
SCT2xxx14 Version: 1.3
Ring-type current transformer
Fig.7: SCT2xxx
Product overview
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.
SCT2xxx 15Version: 1.3
Product overview
Ring-type current transformer
SCT2111 Accuracy class 1,
SCT2121 Accuracy class 0.5,
SCT2211 Accuracy class 1,
SCT2221 Accuracy class 0.5,
SCT2311 Accuracy class 1,
SCT2321 Accuracy class 0.5,
SCT2411 Accuracy class 1,
SCT2421 Accuracy class 0.5,
SCT2515 Accuracy class 1,
SCT2525 Accuracy class 0.5,
SCT2615 Accuracy class 1,
SCT2625 Accuracy class 0.5,
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)
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)
primary current 0…600 A AC / 0…750 A AC, secondary current 1 A AC, max. diameter round conductor 31.8 mm (size 2)
primary current 0…600 A AC / 0…750 A AC, secondary current 1 A AC, max. diameter round conductor 31.8 mm (size 2)
primary current 0…800 A AC / 0…1000 A AC, secondary current 1 A AC, max. diameter round conductor 43.7 mm (size 3)
primary current 0…800 A AC / 1000 A AC, secondary current 1 A AC, max. diameter round conductor 43.7 mm (size 3)
primary current 0…1250 A AC / 0…1500 A AC, secondary current 1 A AC, max. diameter round conductor 43.7 mm (size 4)
primary current 0…1250 A AC / 0…1500 A AC, secondary current 1 A AC, max. diameter round conductor 43.7 mm (size 4)
primary current 0…2000 A AC, secondary current 5 A AC, max. diameter round conductor 54.7 mm (size 5)
primary current 0…2000 A AC, secondary current 5 A AC, max. diameter round conductor 54.7 mm (size 5)
primary current 0…2500 A AC, secondary current 5 A AC, max. diameter round conductor 70 mm (size 6)
primary current 0…2500 A AC, secondary current 5 A AC, max. diameter round conductor 70 mm (size 6)
SCT2xxx16 Version: 1.3
Product overview
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,
SCT3121 Accuracy class 0.5,
SCT3215 Accuracy class 1,
SCT3315 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)
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)
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)
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)
SCT2xxx 17Version: 1.3
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