Siemens SENTRON 3VL series User guide

Switching/protection devices
3VL molded-case circuit breakers
System Manual •03/2009
SENTRON
Answers for industry.

About this document 1
Product-specific information
2
Product description
3
System overview
4
Functions
5
Application planning
6
Installing/mounting
7
Connecting
8
Displays and operator
controls
9
Parameter
assignment/addressing
10
Service and maintenance
11
Technical data
12
Dimensional drawings
13
Circuit diagrams
14
Spare parts/accessories
15
ESD guidelines
A
Appendix
B
SENTRON
Switching/protection devices
3VL molded-case circuit breakers
System Manual
03/2009
110 0110 - 02 DS 01

Legal information
Warning notice system
This manual contains notices you have to observe in order to ensure your personal safety, as well as to prevent
damage to property. The notices referring to your personal safety are highlighted in the manual by a safety alert
symbol, notices referring only to property damage have no safety alert symbol. These notices shown below are
graded according to the degree of danger.
DANGER
indicates that death or severe personal injury will result if proper precautions are not taken.
WARNING
indicates that death or severe personal injury may result if proper precautions are not taken.
CAUTION
with a safety alert symbol, indicates that minor personal injury can result if proper precautions are not taken.
CAUTION
without a safety alert symbol, indicates that property damage can result if proper precautions are not taken.
NOTICE
indicates that an unintended result or situation can occur if the corresponding information is not taken into
account.
If more than one degree of danger is present, the warning notice representing the highest degree of danger will
be used. A notice warning of injury to persons with a safety alert symbol may also include a warning relating to
property damage.
Qualified Personnel
The device/system may only be set up and used in conjunction with this documentation. Commissioning and
operation of a device/system may only be performed by qualified personnel. Within the context of the safety notes
in this documentation qualified persons are defined as persons who are authorized to commission, ground and
label devices, systems and circuits in accordance with established safety practices and standards.
Proper use of Siemens products
Note the following:
WARNING
Siemens products may only be used for the applications described in the catalog and in the relevant technical
documentation. If products and components from other manufacturers are used, these must be recommended
or approved by Siemens. Proper transport, storage, installation, assembly, commissioning, operation and
maintenance are required to ensure that the products operate safely and without any problems. The permissible
ambient conditions must be adhered to. The information in the relevant documentation must be observed.
Trademarks
All names identified by ® are registered trademarks of the Siemens AG. The remaining trademarks in this
publication may be trademarks whose use by third parties for their own purposes could violate the rights of the
owner.
Disclaimer of Liability
We have reviewed the contents of this publication to ensure consistency with the hardware and software
described. Since variance cannot be precluded entirely, we cannot guarantee full consistency. However, the
information in this publication is reviewed regularly and any necessary corrections are included in subsequent
editions.
Siemens AG
Industry Sector
Postfach 48 48
90026 NÜRNBERG
GERMANY
Ordernumber: 3ZX1012-0VL10-0AC1
Ⓟ 03/2009
Copyright © Siemens AG 2009.
Technical data subject to change

3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01 5
Table of contents
1 About this document................................................................................................................................ 11
1.1 Introduction ..................................................................................................................................11
2 Product-specific information..................................................................................................................... 13
2.1 Important notes ............................................................................................................................13
3 Product description.................................................................................................................................. 15
3.1 SENTRON VL overview...............................................................................................................15
3.2 Application overview ....................................................................................................................18
3.3 Configuration................................................................................................................................19
3.3.1 Functional principle ......................................................................................................................19
3.3.2 Subdivision according to power ranges.......................................................................................19
3.3.3 Thermomagnetic overcurrent trip units ........................................................................................20
3.3.4 Electronic overcurrent trip unit (ETU) ..........................................................................................21
3.4 Mechanical operating mechanisms .............................................................................................23
3.4.1 Toggle handle operating mechanism...........................................................................................23
3.4.2 Rotary mechanism on front (optional)..........................................................................................24
3.4.3 Door-coupling rotary operating mechanism (optional).................................................................25
3.5 Motorized operating mechanisms (optional)................................................................................26
3.5.1 Stored-energy motorized operating mechanism..........................................................................27
3.5.2 Motorized operating mechanism without stored-energy mechanism ..........................................27
4 System overview...................................................................................................................................... 29
4.1 Possible applications ...................................................................................................................29
4.2 Key data.......................................................................................................................................30
4.2.1 General data - 3VL molded-case circuit breakers .......................................................................30
4.2.2 General data - auxiliary and alarm switches................................................................................34
4.2.3 General data - Trip units ..............................................................................................................36
4.2.4 General data - motorized operating mechanisms........................................................................38
5 Functions................................................................................................................................................. 41
5.1 Current protection ........................................................................................................................41
5.1.1 Overcurrent trip unit .....................................................................................................................41
5.1.2 Function overview ........................................................................................................................44
5.1.3 Setting options .............................................................................................................................46
5.1.4 Dimensioning short-circuit protection according to frame size ....................................................47
5.1.5 General technical specifications ..................................................................................................48
5.1.6 Differential current protection with RCD module..........................................................................51
5.1.7 Single-pole operation with RCD module......................................................................................56
5.1.8 Ground-fault protection ................................................................................................................58
5.2 Voltage protection ........................................................................................................................60
5.2.1 Undervoltage release...................................................................................................................60
5.2.2 Shunt release...............................................................................................................................62
5.2.3 Auxiliary switches and alarm switches.........................................................................................63
6 Application planning................................................................................................................................. 65

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3VL molded-case circuit breakers
6 System Manual, 03/2009, 110 0110 - 02 DS 01
6.1 Use with frequency converters.................................................................................................... 65
6.2 Use of capacitor banks................................................................................................................ 67
6.3 Primary-side transformer protection............................................................................................68
6.4 Use in DC systems...................................................................................................................... 69
6.5 Use in IT networks ...................................................................................................................... 71
6.6 Use in the motor protection area................................................................................................. 74
6.7 Use in harsh environments: ........................................................................................................ 78
6.8 Use in series connection ............................................................................................................. 81
7 Installing/mounting................................................................................................................................... 83
7.1 Installation methods .................................................................................................................... 83
7.2 Mounting and safety clearances .................................................................................................87
7.3 Locking devices........................................................................................................................... 91
8 Connecting .............................................................................................................................................. 97
8.1 Cables and busbars .................................................................................................................... 97
8.2 Main connection types for fixed mounting................................................................................. 107
8.3 Main connection methods for plug-in and withdrawable version .............................................. 114
8.4 Terminal assignments............................................................................................................... 116
8.5 Auxiliary switch designations .................................................................................................... 118
8.6 Description of the terminals....................................................................................................... 118
9 Displays and operator controls .............................................................................................................. 121
9.1 Overcurrent trip unit without LCD display ................................................................................. 121
9.2 Overcurrent trip unit with LCD display ...................................................................................... 125
9.3 Stored-energy motorized operating mechanism....................................................................... 133
10 Parameter assignment/addressing ........................................................................................................ 135
10.1 Setting the parameters.............................................................................................................. 135
10.2 Setting the protection parameters for motor protection (ETU10M, ETU30M and LCD-ETU
40M) .......................................................................................................................................... 139
11 Service and maintenance ...................................................................................................................... 141
11.1 Preventive measures ................................................................................................................ 141
11.2 Troubleshooting ........................................................................................................................ 143
12 Technical data ....................................................................................................................................... 145
12.1 Technical overview.................................................................................................................... 145
12.2 Configuration of main connections............................................................................................ 150
12.3 Switching capacity overview ..................................................................................................... 153
12.4 Switching capacity overview ..................................................................................................... 157
12.5 Derating factors......................................................................................................................... 159
12.6 Power loss................................................................................................................................. 167

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12.7 Mechanical operating mechanisms ...........................................................................................170
12.8 Motorized operating mechanisms..............................................................................................171
12.9 Capacitor banks .........................................................................................................................173
12.10 Motor Protection.........................................................................................................................174
12.11 RCD modules.............................................................................................................................177
12.12 Undervoltage release.................................................................................................................178
12.13 Undervoltage release connection data ......................................................................................180
12.14 Shunt release.............................................................................................................................182
12.15 Shunt release connection data ..................................................................................................184
12.16 Auxiliary switches and alarm switches.......................................................................................185
12.17 Position signaling switch............................................................................................................187
12.18 Ground fault protection classes .................................................................................................188
12.19 IP degrees of protection.............................................................................................................189
13 Dimensional drawings............................................................................................................................ 191
13.1 VL160X (3VL1), VL160 (3VL2), and VL250 (3VL3), 3- and 4-pole, to 250 A............................191
13.1.1 Circuit breakers..........................................................................................................................191
13.1.2 Operating mechanisms ..............................................................................................................193
13.1.3 Connections and phase barriers................................................................................................195
13.1.4 Terminal covers .........................................................................................................................197
13.1.5 Locking device for the toggle handle .........................................................................................198
13.1.6 Rear locking module ..................................................................................................................198
13.1.7 Accessories................................................................................................................................200
13.1.8 Door cutouts...............................................................................................................................202
13.1.9 Plug-in socket and accessories .................................................................................................204
13.1.10 VL160X (3VL1), 3- and 4-pole, up to 160 A...............................................................................206
13.1.10.1 Plug-in socket and accessories .................................................................................................206
13.1.11 VL160 (3VL) and VL250 (3VL3), 3- and 4-pole, up to 250 A.....................................................208
13.1.11.1 Withdrawable version and accessories .....................................................................................208
13.2 VL400 (3VL4), 3- and 4-pole, up to 400 A .................................................................................211
13.2.1 Circuit breaker............................................................................................................................211
13.2.2 Operating mechanisms ..............................................................................................................212
13.2.3 Connections and phase barriers................................................................................................213
13.2.4 Terminal covers .........................................................................................................................215
13.2.5 Rear interlocking module ...........................................................................................................216
13.2.6 Locking devices, locking device for toggle handle and accessories..........................................216
13.2.7 Door cutouts...............................................................................................................................219
13.2.8 Plug-in socket and accessories .................................................................................................221
13.3 VL630 (3VL5), 3- and 4-pole, up to 630 A .................................................................................227
13.3.1 Circuit breaker............................................................................................................................227
13.3.2 Operating mechanisms ..............................................................................................................228
13.3.3 Connections and phase barriers................................................................................................229
13.3.4 Terminal covers .........................................................................................................................230
13.3.5 Rear interlocking module ...........................................................................................................231
13.3.6 Locking and locking device for toggle handle............................................................................232
13.3.7 Accessories................................................................................................................................233
13.3.8 Door cutouts...............................................................................................................................235
13.3.9 Plug-in socket and accessories .................................................................................................237

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3VL molded-case circuit breakers
8 System Manual, 03/2009, 110 0110 - 02 DS 01
13.3.10 Withdrawable version and accessories..................................................................................... 239
13.4 VL800 (3VL6), 3- and 4-pole, up to 800 A ................................................................................ 242
13.4.1 Circuit breaker........................................................................................................................... 242
13.4.2 Operating mechanisms ............................................................................................................. 243
13.4.3 Withdrawable version................................................................................................................ 244
13.4.4 Connections and phase barriers ............................................................................................... 248
13.4.5 Terminal covers......................................................................................................................... 249
13.4.6 Locking and locking device for toggle handle ........................................................................... 250
13.4.7 Rear interlocking module .......................................................................................................... 251
13.4.8 Accessories............................................................................................................................... 252
13.4.9 Door cutouts.............................................................................................................................. 254
13.5 VL1250 (3VL7) and VL 1600 (3VL8), 3- and 4-pole, up to 1600 A........................................... 256
13.5.1 Circuit breaker........................................................................................................................... 256
13.5.2 Operating mechanisms ............................................................................................................. 258
13.5.3 Withdrawable version................................................................................................................ 260
13.5.4 Connections and phase barriers ............................................................................................... 264
13.5.5 Terminal covers......................................................................................................................... 265
13.5.6 Rear interlocking module .......................................................................................................... 268
13.5.7 Locking and locking device for toggle handle ........................................................................... 269
13.5.8 Accessories............................................................................................................................... 269
13.5.9 Door cutouts.............................................................................................................................. 271
13.5.10 Current transformer................................................................................................................... 272
13.6 VL160X (3VL1) up to VL800 (3VL6), 3- and 4-pole, up to 800 A ............................................. 273
13.6.1 Locking with bowden wire ......................................................................................................... 273
13.6.2 Busbar adapter system 8US1 ................................................................................................... 275
13.7 VL160X (3VL1) with RCD block, 3- and 4-pole, up to 160 A.................................................... 276
13.7.1 Circuit breakers ......................................................................................................................... 276
13.7.2 Connections and phase barriers ............................................................................................... 277
13.7.3 Terminal covers......................................................................................................................... 279
13.7.4 Door cutouts.............................................................................................................................. 281
13.7.5 Plug-in socket and accessories ................................................................................................ 283
13.8 VL160 (3VL2) and VL250 (3VL3) with RCD module, 3- and 4-pole, to 250 A.......................... 285
13.8.1 Circuit breakers ......................................................................................................................... 285
13.8.2 Connections and phase barriers ............................................................................................... 286
13.8.3 Terminal covers......................................................................................................................... 288
13.8.4 Door cutouts.............................................................................................................................. 290
13.8.5 Plug-in socket and accessories ................................................................................................ 292
13.9 VL400 (3VL4) with RCD module, 3- and 4-pole, up to 400 A................................................... 298
13.9.1 Circuit breakers ......................................................................................................................... 298
13.9.2 Connections and phase barriers ............................................................................................... 300
13.9.3 Terminal covers......................................................................................................................... 302
13.9.4 Door cutouts.............................................................................................................................. 304
13.9.5 Plug-in socket and accessories ................................................................................................ 306
13.10 Door-coupling rotary operating mechanisms 8UC.................................................................... 312
13.11 4NC current transformers for measuring purposes .................................................................. 315
13.12 COM20/COM21 (communications module for SENTRON 3VL)............................................... 316
13.13 COM10/COM 11 (communications module for SENTRON 3VL).............................................. 316
14 Circuit diagrams..................................................................................................................................... 317

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System Manual, 03/2009, 110 0110 - 02 DS 01 9
15 Spare parts/accessories ........................................................................................................................ 329
15.1 Installation..................................................................................................................................329
15.2 Electromechanical components.................................................................................................333
15.3 Mechanical components ............................................................................................................335
15.4 Electrical/electronic engineering ................................................................................................337
A ESD guidelines ...................................................................................................................................... 339
A.1 ESD Directive.............................................................................................................................339
B Appendix................................................................................................................................................ 341
B.1 Selectivity...................................................................................................................................341
B.2 Conversion tables ......................................................................................................................344
B.3 Standards and specifications.....................................................................................................346
B.4 Ordering data .............................................................................................................................348
Glossary ................................................................................................................................................ 351

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3VL molded-case circuit breakers
10 System Manual, 03/2009, 110 0110 - 02 DS 01

3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01 11
About this document 1
1.1 Introduction
Purpose of this manual
This manual is intended for reference purposes. The information in this manual enables you
to configure and operate the SENTRON VL system.
Audience
This manual is aimed at people with the required qualifications to commission and operate
the SENTRON VL system.

About this document
1.1 Introduction
3VL molded-case circuit breakers
12 System Manual, 03/2009, 110 0110 - 02 DS 01

3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01 13
Product-specific information 2
2.1 Important notes
Validity
This manual applies to SENTRON circuit breakers with the following designations:
● VL160X
● VL160
● VL250
● VL400
● VL630
● VL800
● VL1250
● VL1600
Standards and certifications
The SENTRON VL circuit breakers comply with the standards:
● IEC 60947-2 / DIN EN 60947-2 (VDE 0660-101)
● IEC 60947-1 / DIN EN 60947-1 (VDE 0660-100)
● Isolating features in accordance with IEC 60947-3 / EN 60947-3 (VDE 0660-107)
● Network disconnection features for stopping and shutting down in an emergency (main
switch and EMERGENCY-OFF switch) in accordance with IEC 60204-1 / DIN EN 60204-
1 (VDE 0113-1)
Disclaimer of liability
The products described here were developed to perform safety-oriented functions as part of
an overall installation or machine. A complete safety-oriented system generally features
sensors, evaluation units, signaling units, and reliable shutdown concepts. It is the
responsibility of the manufacturer to ensure that a system or machine is functioning properly
as a whole. Siemens AG, its regional offices, and associated companies (hereinafter referred
to as "Siemens") cannot guarantee all the properties of a whole plant or machine that has
not been designed by Siemens.

Product-specific information
2.1 Important notes
3VL molded-case circuit breakers
14 System Manual, 03/2009, 110 0110 - 02 DS 01
Nor can Siemens assume liability for recommendations that appear or are implied in the
following description. No new guarantee, warranty, or liability claims beyond the scope of the
Siemens general terms of supply are to be derived or inferred from the following description.
Up-to-the-minute information
You can obtain further assistance by calling the following numbers:
Technical Assistance: Telephone: [phone] (8°° - 17°° CET)
Fax: [phone]
or on the Internet at:
e-mail: [email protected]
Internet: www.siemens.de/lowvoltage/technical-assistance
Technical Support:
Telephone: [phone]
Correction sheet
A correction sheet is included at the end of the manual. Please use it to record your
suggestions for improvements, additions and corrections, and return the sheet to us. This will
help us to improve the next edition of the manual.

3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01 15
Product description 3
3.1 SENTRON VL overview
SENTRON VL circuit breakers are resistant to extreme climates. They are designed for use
in closed rooms where no onerous operating conditions prevail (e.g. dust, caustic vapors,
hazardous gases).
SENTRON VL types
The type designations of all available circuit breakers are oriented around the rated current
Type designation Maximum rated current (A)
VL160X 160
VL160 160
VL250 250
VL400 400
VL630 630
VL800 800
VL1250 1250
VL1600 1600

Product description
3.1 SENTRON VL overview
3VL molded-case circuit breakers
16 System Manual, 03/2009, 110 0110 - 02 DS 01
Type plate and ID number
The figure shows all the operator elements, setting options and names corresponding to the
precise specified use of the circuit breaker.
















(1) Specified frame size
(2) Circuit breaker type
(3) Display of switching capacity
(4) Rating plate
(5) Accessories ID fields
(6) Catalog number (machine-readable product code)
(7) Overcurrent adjustment
(8) In rated current of the circuit breaker
(9) Overcurrent tripping type TM (thermomagnetic)
(10) Reference temperature
(11) Short-circuit tripping/adjustment
(12) Test key
(13) Toggle handle with 3 positions
(14) Switching capacity
(15) Standards
(16) Accessories cover (removable)
Figure 3-1 SENTRON VL circuit breakers - labeling and operator elements

Product description
3.1 SENTRON VL overview
3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01 17
SENTRON VL accessories














 















(1) Withdrawable/plug-in socket (13) Door-coupling rotary operating mechanism
(2) Withdrawable side panels (14) SENTRON 3VL circuit breaker
(3) Phase barriers (15) Internal accessories
(4) Flared busbar extensions (16) Electronic overcurrent trip unit LCD ETU
(5) Straight connecting bars (17) Electronic overcurrent trip unit with communication function
(6) Multiple feed-in terminal for Al/Cu (18) Thermal/magnetic overcurrent trip unit
(7) Box terminal for Cu (19) RCD module
(8) Extended terminal cover (20) Rear terminals – flat and round
(9) Standard terminal cover (21) COM10 communication module for PROFIBUS-DP
(10) Masking/cover frame for door cutout (22) COM20 communication module for PROFIBUS-DP
(11) Stored-energy motorized operating
mechanism
(23) Battery power supply with test function
(12) Front rotary operating mechanism
Figure 3-2 SENTRON VL accessories

Product description
3.2 Application overview
3VL molded-case circuit breakers
18 System Manual, 03/2009, 110 0110 - 02 DS 01
3.2 Application overview
The following overview shows the most frequently occurring applications
Application overview
Application Type Description
3- and 4-pole circuit breakers
VL160X
VL160
VL250
VL400
VL630
VL800
VL125
VL1600
Line protection
The trip units for line protection are designed to protect cables and non-
motorized loads against overload and short-circuit.
3-pole circuit breaker
VL160
VL250
VL400
VL630
Motor/generator protection
The overload and short-circuit releases are designed for optimum
protection and direct-online starting of AC squirrel-cage motors. The
circuit breakers for motor protection have phase-failure sensitivity and a
thermal memory that protects the motor against overheating. The
adjustable time lag class enables users to adjust the overload release
to the startup conditions of the motor to be protected.
3-pole circuit breaker
VL160
VL250
VL400
VL630
Starter combination
Starter combinations consist of: Circuit breaker + contactor + overload
relay. The circuit breaker handles short-circuit protection and the
isolating function. The contactor has the task of switching the load
feeder normally. The overload relay handles overload protection that
can be specially matched to the motor. The circuit breaker for starter
combination is therefore equipped with an adjustable and non-delayed
short-circuit release.
3- and 4-pole circuit breakers
VL160X
VL160
VL250
VL400
VL630
VL800
VL1250
VL1600
Non-automatic air circuit breakers
These circuit breakers are used as incoming circuit breakers, main
switches or isolating switches without overload protection. They have
fixed short-circuit releases so that back-up fuses are not necessary.

Product description
3.3 Configuration
3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01 19
3.3 Configuration
3.3.1 Functional principle
Design - mechanical principle
All SENTRON VL circuit breakers have a trip-free mechanism that ensures the trip process
is not prevented even if the operating mechanism is blocked or manually held in the "ON"
position.
The contacts are opened and closed by a toggle handle positioned in the center. This is
attached to the front side on all circuit breakers.
All SENTRON VL circuit breakers are "joint trip units". This means all contacts open or close
simultaneously when the circuit breaker toggle handle is moved from "OFF" to "ON" or from
"ON" to "OFF", or when the tripping mechanism is activated by an overcurrent or with the
help of an auxiliary trip (shunt release or undervoltage release).
Current limiting
The SENTRON VL circuit breakers are designed on the principle of magnetic repulsion of
the contacts. The contacts open before the expected peak-value of the short-circuit current is
reached. Magnetic repulsion of the contacts very significantly reduces the thermal load I2t as
well as the mechanical load resulting from the impulse short-circuit current IP of the system
components that occur during a short-circuit.
You can find more information in Chapter Use in the motor protection area (Page 74).
3.3.2 Subdivision according to power ranges
VL160X circuit breakers
The most important components of the VL160X circuit breakers are the three current paths
with the incoming and outgoing terminals. The fixed and movable contacts are arranged in
such a way as to guarantee magnetic repulsion of the contacts. In conjunction with the arc
splitter chambers, a dynamic impedance is created that causes a current limitation through
the reduction in the harmful effects of I2t and the Ip energy resulting from short-circuits.
The overcurrent trip unit is a thermomagnetic device installed at the factory. It is equipped
with fixed or adjustable overload releases and a fixed short-circuit release in each pole.
To the right and left of the centrally positioned toggle handle of every SENTRON VL circuit
breaker is a double-insulated accessories compartment for installing auxiliary switches or
alarm switches as well as voltage and undervoltage releases.

Product description
3.3 Configuration
3VL molded-case circuit breakers
20 System Manual, 03/2009, 110 0110 - 02 DS 01
VL160 to VL630 circuit breakers
The arrangement of current paths, contact configuration and switch mechanism of the VL160
to VL630 circuit breakers corresponds to that of the VL160X circuit breaker. The designs
diverge with regard to the overcurrent trip unit.
● The overcurrent trip units are available in a thermomagnetic version and in an electronic
version.
● The overcurrent trip units can be installed or replaced on-site without special tools.
● Thermomagnetic overcurrent trip units are available with adjustable overload releases
and short-circuit releases.
VL800 bis VL1600 circuit breakers
The arrangement of the current paths and switch mechanisms is identical to that of the
VL160X to VL630 circuit breakers.
However, the VL800 to VL1600 circuit breakers are only available in the version with
electronic overcurrent trip unit. As with all electronic overcurrent trip units for the SENTRON
VL circuit breakers from Siemens, the current transformers (one per phase) are
accommodated within the overcurrent trip unit housing. They transmit a signal proportional to
the load current to the electronic trip unit.
All SENTRON VL circuit breakers with electronic trip units measure the actual effective
current. This method is the most accurate way of measuring currents in electrical distribution
systems with extremely high harmonics.
3.3.3 Thermomagnetic overcurrent trip units
Thermomagnetic overcurrent trip units
A thermomagnetic overcurrent trip unit consists of two components - a thermal release for
protecting against overload, and a magnetic release for protecting against short-circuit. Both
trip unit components are switched in series.
The thermal trip unit
consists of a temperature-dependent bimetal that heats up as a result of the flow of current.
This means the release is current-dependent. The heating of the bimetal strip depends on
the ambient temperature of the circuit breaker. All current values specified for 3VL for
thermomagnetic trip units refer to an ambient temperature of 40°C. Where ambient
temperatures deviate from this, the values in the tables in Chapter Derating factors
(Page 159) are to be used.