ABB Fieldbus Infrastructure and Network Devices An overview

Transcription

1 ABB Fieldbus Infrastructure and Network Devices An overview ABB

2 ABB fieldbus devices Industrial automation with the fieldbus Fieldbus technology is becoming increasingly important throughout industry. This isn t really surprising as the principle behind it is as simple as it is ingenious: in addition to supplying connected devices with power, the fieldbus for process automation is also used to process purely digital communication between the field and the process control system. This makes it possible to partially relocate open-loop and closedloop control functions within the hierarchy from the system to the field devices, therefore allowing system optimization functions at the higher system level to be put to better use. ABB systems and components ABB has a reputation as a successful equipment supplier offering a wide range of tried and tested systems for industrial automation. This brochure contains information about ABB s range of fieldbus components with specific functionality that can be used for both fieldbuses PROFIBUS and FOUN DATION Fieldbus. These two bus systems are the accepted fieldbus standards in the automation sector. The following topology examples for PROFIBUS and FOUNDATION Fieldbus indicate possibilities for using the following fieldbus devices: Examples of system topology with PROFIBUS Control network AC 870P AC 800F AC 800M PROFIBUS DP PROFIBUS Barrier BI 913S LD 800P Profibus EExi S900 I/O PROFIBUS PA Fieldbus Barrier FB 900 series S900 CB 220 Compact Box PA device 2 ABB

3 Overview of the devices presented below: Thanks to their interoperability, the devices presented in this brochure facilitate the task of project planning for the fieldbus and prevent communication errors. Both physically and in terms of functionality, ABB s fieldbus components are ideally prepared for their specific use in the field. Depending on the device, using ABB fieldbus devices delivers the following advantages: The bus segment is protected against communication errors and short-circuits EEx i field devices can be connected during operation No further T boxes or distribution boxes are needed A higher supply voltage and a higher supply current are made available, therefore increasing the segment length and making it possible to connect up to 32 field devices to a single segment Fieldbus Barrier page 4 Series FB 900-S Power Conditioner page 6 PC 900-NR FOUNDATION Fieldbus Linking Device page 8 LD 800HSE PROFIBUS DP/PA Linking Device page 10 LD 800P PROFIBUS Redundancy Linking Module page 14 RLM01 Annex A: Grounding and shielding page 16 Annex B: Introduction to intrinsic safety page 18 Examples of system topology with FF Control network AC 800F AC 800M FF HSE network LD 800HSE Power Conditioner PC 900-NR H1 link Fieldbus Barrier FB 900-series Max. 4 Fieldbus Barriers H1 devices ABB 3

4 Feldbus Barriere, series FB 900-S The Fieldbus Barrier series FB 900-S can be used to connect up to four intrinsically safe fieldbus stations. They are connected, using non-intrinsically safe ports, to the trunk of a fieldbus with physical bus characteristics according to IEC A Fieldbus Barrier works exclusively on the physical level, making it independent of the protocol. As a result, it can be used for any fieldbus with physical bus characteristics according to IEC , i.e. for FOUNDATION Fieldbus and PROFIBUS PA, for example. The Fieldbus Barrier performs the following tasks: Option of connecting intrinsically safe (EExi) field devices Feeding of field devices connected at the outputs Assurance of electrical isolation between the fieldbus segment that is not intrinsically safe (fieldbus trunk) and the intrinsically safe spur outputs Protection against short-circuits at the intrinsically safe spur outputs Using the Fieldbus Barrier has the following advantages: Interference-free communication: As a result of the short-circuit current restriction at the output, only the output concerned fails in the event of a line short-circuit between the Fieldbus Barrier and the field device. The fieldbus segment continues to work and communication at this bus line can therefore be maintained without interruption with all other stations. High availability: The EExi field device connection makes it possible to exchange field devices during operation. Reduction of repeaters/linking Devices: Only Power Repeaters/Linking Devices without an intrinsically safe interface are needed. Reduction of distribution boxes: The Fieldbus Barrier meets the requirements of protection classes IP66 and IP67. It replaces the T-Trunk connection box needed for conventional fieldbus wiring. Cascading/continuation of the fieldbus is possible. Thanks to internal, switchable termination, there is no need for additional assembly of external active fieldbus scheduling. H1 link PROFIBUS DP Fieldbus Barrier FB 900 series LD 800P PROFIBUS PA H1 devices Fieldbus Barrier FB 900 series The Fieldbus Barrier in a FOUNDATION Fieldbus environment PA devices 4 The Fieldbus Barrier in a PROFIBUS environment ABB

5 High operational reliability: As a result of using the Increased safety protection type, the maximum permissible current on the EExe side is only limited by the Power Conditioner (in the case of FOUNDATION Fieldbus) or Linking Device (in the case of PROFIBUS PA) that is used. As a result, by using the Power Conditioner or the Linking Device in conjunction with the Fieldbus Barrier, a larger number of field devices can be connected to a single segment without affecting operational reliability. Electrical isolation: As a result of the electrical isolation between the field devices and the system, the need for equipotential bonding is eliminated. Simplified ex-loop check: The Fieldbus Barrier meets the requirements of the FISCO model (see page 18). This means that there is no need to test EExi loops with regard to hazardous areas when FISCO field devices are used. Based on the FB 900-S series, ABB offers three different types of Fieldbus Barrier All types of Fieldbus Barrier have EExe terminal units for the fieldbus and additional EExi terminal units for connecting up to four field devices. They can be assembled directly in hazardous areas (Zone 1 or Zone 2 in accordance with ATEX). FB 900-SA4 in the field housing, made of aluminum, for direct field assembly on a wall or on armatures with cable entries made of plastic. FB 900-SB4 in the field housing, made of stainless steel, for direct field assembly on a wall or on armatures with cable entries made of stainless steel. FB 900-SR4 without field housing, for assembly on a 35 mm top-hat rail in accordance with EN in a cabinet or field housing. ABB 5

6 Power Conditioner PC 900-NR As standard, the PC 900-NR Power Conditioner delivers a 24 V d.c. power supply for fieldbus networks. In addition, it ensures the necessary impedance matching for networks in accordance with IEC / ISA S50.02 (FOUNDATION Fieldbus). The PC 900-NR Power Conditioner can be used for fieldbuses which are not operated intrinsically safely for explosion protection for instance in the case of non-hazardous applications or installations with explosion protection with an increased level of EExe safety. The PC 900-NR Power Conditioner is assembled outside the hazardous area. If it is used in conjunction with the Fieldbus Barrier (see pages 4-5), EExi signals can also be connected. The Power Conditioner supplies the H1 link with a current of up to 1 A. It has integrated termination, two LEDs to display the current and errors (overload, short-circuit, low voltage), and removable terminals to simplify installation. To the field devices H1 segment with 1 A Using the Power Conditioner has the following advantages: H1 host Flexible fieldbus segment structure: As a current of 1 A is supplied, the fieldbus length can be increased and the theoretically permissible number of up to 32 field devices can be connected. This theoretical number is only limited by the bus timing. High availability: Using the Power Conditioner in conjunction with the Termination Unit or Power Feed Modules simplifies the wiring and, as a result of the high MTBF time of the Power Conditioner, increases the reliability of the fieldbus. Simplified topology structure: The Power Conditioner has a bus terminator that can be connected and switched off. 24 V d.c. Error output 6 ABB

7 Example of a Power Conditioner with a Power Rail with a redundant power supply via redundant Power Feed Modules To the field devices H1 segment at 1 A each Power Conditioner Power Feed Module Redundant Power Feed Module Power Rail Optional: redundant 24 V d.c. input 24 V d.c. 24 V d.c. Error output Error output The following components are Power Conditioner accessories, which can be used to simplify assembly and increase availability Power Feed Module A PF 900-NR Power Feed Module provides the power supply for the Power Conditioner. It is only needed when the Power Rail is used. Use of the Power Feed Module has the following features: A redundant power supply can be provided for the Power Conditioner. The 24 V d.c. voltage is made available via the internal wiring. Device redundancy with integrated monitoring is possible. Power Rail The PR 900-NR Power Rail is a voltage distribution rail for the Power Conditioner. Its size allows it to be fitted on a standardized DIN rail without additionally attaching the rail. Termination Unit The TU 900-NR4 Termination Unit contains the PR 900-NR Power Rail and the terminals for the H1 links, for the error messages, and for the redundant external 24 V d.c. power supply. The Termination Unit can be used to mount up to four PR 900-NR Power Conditioners and up to two PF 900-NR Power Feed Modules. It simplifies the task of integrating the devices while at the same time reducing the amount of wiring involved. The availability of the H1 link fieldbus segment can be increased by using a Termination Unit with Power Conditioners and Power Feed Modules. This allows Power Feed Modules to be made redundant and provides a means of redundantly connecting external 24 V d.c. power supplies. ABB 7

8 FOUNDATION Fieldbus Linking Device LD 800HSE LD 800HSE serves as a gateway between the FOUNDATION Fieldbus field devices on H1 links and High Speed Ethernet (HSE Subnet). The provision of data from an H1 link to the HSE Subnet as well as from one H1 link to another is guaranteed by the cyclical communication typical of FOUNDATION Fieldbus between field devices on various H1 links and field devices on the HSE Subnet. In addition, the client/server gateway allows function blocks in H1 devices to be accessed via the HSE interface. LD 800HSE is also designed for redundant use, with the relevant H1 outputs for two Linking Devices being connected to an H1 link. The redundant Linking Devices are interconnected via a serial interface for the purpose of exchanging redundancy information. LD 800HSE is mounted on a DIN rail and corresponds to protection class IP 20. The LD 800HSE allows users to access devices on the FOUNDATION Fieldbus (FF) H1 link via High Speed Ethernet from control system consoles or from central management consoles. The LD 800HSE allows reports and alarms to be distributed from H1 devices. It works as a Link Master for each H1 link with the Link Active Scheduler (LAS) functionalities as the basis for publisher/subscriber communication scheduling. The integrated Web server allows diagnostic data and functions to be accessed remotely using a Web browser. The design of FOUNDATION Fieldbus Linking Device LD 800HSE corresponds to class 42c of the HSE profile and is registered with the Fieldbus Foundation1). Data exchange between H1 links of the same Linking Device as well as between those of different Linking Devices is carried out via publish/subscribe mechanisms and does not require any IEC controller configurations. IEC controllers can be coupled via HSE interface modules. Thanks to its simple assembly and connection technology, the LD 800HSE is quite easy for users to work with. Comprehensive diagnosis options are made possible by the device s communication and status displays as well as the integrated Web server. In addition, the various certifications guarantee that international standards are adhered to, thus ensuring that they can be integrated smoothly into systems. Functions and benefits: Connection between FOUNDATION Fieldbus High Speed Ethernet (HSE) and up to four H1 links Configuration of the connected H1 devices Access to the function blocks in the H1 devices (client/server) 4 independent H1 Link Masters (LAS) Publish/subscribe (H1) (with up to 4 sub-cycles) Transfer of data from one H1 link to another Transfer of data between H1 and HSE Update of the firmware using download mechanisms Redundancy thanks to a second Linking Device with automatic data synchronization via a serial interface 1) LD 800HSE is registered as a class 42a device because the foundation does not offer class 42c registration at present. 8 ABB

9 Technical data for FOUNDATION Fieldbus Linking Device LD 800HSE Power supply Supply voltage 24 V d.c. (+- 20%) Current consumption Structure Dimensions Weight Protection rating Ambient conditions Operating temperature Storage temperature Relative humidity Ethernet interface HSE Number of channels 1 Port Transfer rate Fieldbus interface H1 Number of H1 channels 4 Port Physical layer profile Transfer rate Serial interface Port Certifications Accessories 200 ma (height x width x depth) 131 x 47 x 111 mm approx. 0.4 kg IP20 0 C C, non-vertical mounting and any impairment in air convection may reduce the upper temperature limit -20 C C < 90%, non-condensing Ethernet 10BASE-T/100BASE-TX, RJ45 10 Mbit/s or 100 Mbit/s (auto-sensing) FF H1 3-pole screw terminal (pluggable), functionally isolating FF-816, type 114 separately powered, not intrinsically safe kbit/s 1 x 9-pole SubD pin (male) RS-232, kbit/s CE in accordance with EMC Directive 89/336/EEC EN , EN FCC Part 15 Subpart B Class A VCCI Class A Information Technology Equipment (ITE) ULC ABB Industrial IT enabled Redundancy link cable 0.5 m (to be ordered separately) ABB 9

10 PROFIBUS DP/PA Linking Device LD 800P Linking Devices are needed to connect PROFIBUS DP to PROFIBUS PA. The LD 800P Linking Device converts the physical bus characteristics of the RS 485 interface for the PROFIBUS DP into PROFIBUS PA physical bus characteristics according to IEC , enables connected PROFIBUS PA devices to be supplied with power via the bus, and allows use in hazardous areas if so required. The LD 800P is a modular Linking Device consisting of a Head Station and Power Link Modules. The Head Station, which is used to convert the PROFIBUS DP protocol to PROFIBUS PA, is available in three models: HS 810: 1-channel HS 820: 2-channel HS 840: 4-channel, with the additional feature that it supports line redundancy on the PROFIBUS DP side The PL 810 and PL 890 Power Link Modules supply the connected PROFIBUS PA devices with power via the fieldbus line, which means that the field devices do not require an external power supply and costs are therefore reduced. The PL 890 Power Link Module offers an intrinsically safe connection in accordance with [EEx ia] IIC and is approved in line with FISCO (see Annex). Both types of Power Link Module integrate bus termination and can be operated in parallel on a Head Station. 10 ABB

11 These five different modules allow PROFIBUS PA segments to be set up flexibly in such a way as to maximize performance and minimize costs. Up to five Power Link Modules can be connected to one of the Head Station s PROFIBUS PA channels, making it possible to set up a maximum of 20 PROFIBUS PA segments. All modules are mounted on a DIN rail and are approved for operation and installation in Zone 2 hazardous areas in accordance with CENELEC. All standardized PROFIBUS DP transmission rates of kbit/s to 12 Mbit/s are recognized and supported automatically. Properties The LD 800P Linking Device works transparently, which means that neither the PROFIBUS DP nor the PROFIBUS PA consider LD 800P to be a station. As a result, it is not necessary to address, configure, or parameterize the Linking Device. The optionally redundant PROFIBUS DP connection allows high availability in terms of the communications networks. The Power Link Modules integrate a Power Conditioner separating data communication from the bus power supply. Depending on the available power, up to 400 ma can be fed to the PA segment using PL 810 and up to 100 ma can be fed using PL 890, which is certified in accordance with FISCO. Devices that are certified in accordance with FISCO are proven to be intrinsically safe and can be used in a plant s hazardous areas without the need for additional calculation effort. In addition, the Power Link Modules possess an integrated bus terminator, which terminates the PROFIBUS PA line unilaterally. There is therefore no need for a separate bus terminator on the Power Link Modules. The fieldbus and power terminals that are located on the modules are electrically isolated from one another. Universal The LD 800P PROFIBUS DP/PA Linking Device can be used in all ABB systems and in all non- ABB systems that support PROFIBUS: System 800xA Freelance 800F AC 870P/Symphony Melody Advant Master Non-ABB systems, such as PLC with a PROFIBUS interface Advantages for the customer The LD 800P PROFIBUS DP/PA Linking Device is a simple solution for connecting PROFIBUS PA devices to ABB process control systems or to PCSs from other manufacturers. Thanks to the fact that it is easy to assemble and connect, users are offered easy handling as well as extensive diagnostic options using the communication and status displays located on the device. In addition, the various certifications guarantee that international standards are adhered to, therefore ensuring smooth operation in systems. ABB 11

12 PROFIBUS DP/PA Linking Device LD 800P Technical data for the HS 810, HS 820, and HS 840 Head Stations Rated operational voltage Rated normal current V DC Ripple < 10 % Power dissipation Electrical isolation PROFIBUS DP fieldbus connection ma (without load) 3 W Functional insulation, rated insulation voltage 50 V mns 9-pol. Sub-D jack (RS 485), for HS 840 also redundant Fieldbus standard PROFIBUS DP/V1 in line with EN 50170/2 Baud rate Electrical isolation EN Electromagnetic compatibility EC Guidelines Standards 45,45 kbit/s Mbit/s NAMUR NE 21 89/336/EWG EN Ambient temperature C ( K) Relative humidity < 75 % Connection type Terminals Core cross-section Up to 2,5 mm 2 Casing Weight Protection rating in line with DIN Data relating to use in hazardous areas Approval for Zone 2 Group, category, protection type Explosion protection EC Guidelines Standards 60 mm x 115 mm x 107 mm 250 g IP20 TÜV 02 ATEX 1888X Ex II 3 G EEx n A II T4 EG94/9 EN HS 810, HS 820, and HS 840 Head Stations PL 810 and PL 890 Power Link Modules Power Link Modules for use in hazardous areas 12 ABB

13 Technical data for the PL 810 and PL 890 Power Link Modules Rated operational voltage Rated normal current V DC Ripple < 10 % Electrical isolation 790 ma ma PROFIBUS PA In line with IEC PL 810/PL 890 rated operational voltage PL 810/ PL 890 rated normal current Terminating impedance Protocol Baud rate Functional insulation, rated insulation voltage 50 V mns V DC/12, ,4 V DC < 400 ma/< 100 ma 100 ohms integrated PROFIBUS PA 31,25 kbit/s Electrical isolation EN Protection rating IEC/EN Electromagnetic compatibility EC Guidelines Standards NAMUR NE 21 89/336/EWG EN Ambient temperature C ( K) Relative humidity < 75 % Connection type Terminals Core cross-section Up to 2,5 mm 2 PL 810/PL 890 casing PL 810/PL 890 weight Protection rating in line with DIN Data relating to use in hazardous areas Approval for Zone 2 Group, category, protection type Explosion protection EC Guidelines Standards Also for PL 890: Group, category, in line with EC94/9 Protection type U o voltage I o current P o power 80 mm x 115 mm x 107 mm/100 mm x 115 mm x 107 mm 320 g/430 g IP20 TÜV 02 ATEX 1886X/TÜV 02 ATEX 1887X Ex II 3 G EEx n A IIC T4 EG94/9 EN EX II (1) G D [EEx ia] IIC 15 V 207,2 ma 1,93 W ABB 13

14 PROFIBUS Redundancy Linking Module RLM01 Designing fieldbus lines to be redundant considerably increases the availability of plants or plant components. Module RLM01 provides redundant communication channels for the PROFIBUS protocol. Like an active change-over switch, it transforms a PROFIBUS-DP line into two redundant lines or, conversely, combines two redundant lines to form a single line, as required. This also makes it possible for field devices that are fitted with just one PROFIBUS interface to be integrated into redundant lines. Universal Full redundancy can only be achieved if both the control unit and the field devices support this. However, the RLM01 module can be used universally in any PROFIBUS configuration for instance in order to allow redundant PROFIBUS lines even if the control unit or field devices are not designed to be redundant. Properties Use of PROFIBUS-DP/FMS lines Implementation of a non-redundant PROFIBUS line on two redundant lines and vice versa Automatic line selection Transmission rate of 9.6 kbit/s - 12 Mbit/s Communication monitoring Repeater functionality Redundant power supply Status and error display Power supply monitoring Signaling contact Easy assembly on a DIN mounting rail Application The RLM01 module can be positioned directly after a master, in front of a bus segment with several slaves, or in front of an individual slave. Several PROFIBUS stations with redundant couplers can be connected directly to the PROFIBUS that has been made redundant by RLM01. Stations with just one interface can be positioned either on the A line or on the B line. Each RLM01 PROFIBUS interface can operate up to 31 PROFIBUS stations. 14 ABB

15 Line redundancy: As shown in the diagram, the three interfaces of RLM01 A, B, and M support transmission rates of 9.6 kbit/s to 12 Mbit/s, which are defined for PROFIBUS-DP/FMS. The module reinforces die signal form and amplitude of the data received and monitors all three lines with regard to activity and faults. Any faults that are recognized are indicated with the aid of a LED on the front panel. Suitable messages are available for diagnostic purposes and can be picked up on the 8-pole terminal strip. Splitting a non-redundant line: Data arriving via line M with the correct start of frame is passed in parallel to the other two connections, A and B. If the start of frame is incorrect, the control logic does not output any data at A and B. Either a simple or a redundant power supply with 24 V d.c. is possible as required. The monitoring logic checks whether both voltages are available and reports any malfunction that may occur. Combining redundant lines: The data that arrives first via line A or line B, with the correct start of frame, is forwarded to connection M. If the data arrives at the same time, either line A or line B is selected at random. If the start of frame at A is incorrect, the control logic switches to line B, which is still available and redundant. The procedure is the same in reverse for line B. Line redundancy Master 1 Master 2 RLM 01 O O Line A E E Line B A B Slave 1 RLM 01 Slave 3 R R M Slave 2 Slave 5 K K Slave 4 Slave N ABB 15

16 Annex A: Grounding and shielding Using the Fieldbus Barrier and Power Conditioner devices increases the operational reliability of systems that are fitted with fieldbus technology. When it comes to planning fieldbus topologies in hazardous areas, issues relating to explosion protection must be taken into account. This includes using permissible cable types, observing grounding and shielding regulations, and proving explosion protection. Grounding and shielding the Fieldbus Barrier All cable types that comply with the standard have a shield. For reasons of EMC protection, this shield should be grounded. Use of the Fieldbus Barrier makes it possible to use all recognized shielding and grounding strategies: Hard grounding of the shield on both sides (connection between the shield and equipotential bonding) Capacitive grounding at one end of the shield (connection of the shield to the equipotential bonding via a capacitor), hard grounding at the other end Hard grounding at one end of the shield, no grounding at the other end ABB always recommends the use of shielded lines for the fieldbus. 16 ABB

17 Cabling It is advisable to use the following cable types with the characteristic values listed in the table: Type A Type B Cable structure Twisted pair of wires, shielded One or more twisted pair of wires, overall shield Wire cross section (nominal) 0,8 mm 2 (AWG 18) 0,32 mm 2 (AWG 22) Loop resistance (direct current) 44 Ω/km 112 Ω/km Surge resistance at kh 100 Ω ±20 % 100 Ω ±30 % Wave attenuation at 39 khz 3 db/km 5 db/km Capacitive imbalance 2 nf/km 2 nf/km Group delay distortion 7.9 khz khz 1,7 µs * Degree of cover of the shield 90 % * Maximum network expansion for non-intrinsically-safe applications Maximum network expansion for intrinsically safe applications 1900 m 1200 m 1000 m * ABB 17

18 Annex B: Introduction to intrinsic safety The fieldbus systems in hazardous areas require the use of the increased safety (EExe) and intrinsic safety (EExi) protection types. The increased safety (EExe) protection type is used when powering fieldbuses. All devices are fitted with permissible terminals for this. Use of the intrinsic safety (EExi) protection type in the field allows the devices to be connected or exchanged while the system is in operation. When the EExi protection type is used, proof of intrinsic safety must be furnished. Two different models can be used for this: The FISCO model The Entity model The FISCO model The FISCO model was developed by the German Physical Technical Institute (PTB) and published in report PTB-W-53 Untersuchung zur Eigensicherheit bei Feldbus-Systemen (Investigation of intrinsic safety in fieldbus systems). FISCO stands for Fieldbus Intrinsically Safe COncept. This model is based on the following requirements: 1. To transmit electrical power and data, the bus system uses the Manchester Bus Powered physical layout in accordance with IEC This is the case both for FOUNDATION Fieldbus and for PROFIBUS PA. 2. Only one active source is allowed on a single bus segment (the Power Repeater/the Linking Device/ the Fieldbus Barrier). All other bus stations act as passive current sinks. 3. The basic current consumption of a bus station is at least 10 ma. 4. For each bus station (Ui, Ii, Pi), the following must be guaranteed: Ui Uo for the Linking Device/the Power Repeater/the Fieldbus Barrier Ii Io for the Linking Device/the Power Repeater/the Fieldbus Barrier Pi Po for the Linking Device/the Power Repeater/the Fieldbus Barrier 5. Each bus station (Ci, Li) must meet the following condition: Ci 5 nf Li 10 μh 6. The permissible line length for EEx ia IIC applications is 1000 m. 7. The permissible spur length for explosion protection applications is 60 m per spur line. The definition of the spur must be observed here. 8. The transmission line used must conform to the following cable parameters: Resistance per unit length: 15 Ω/km < R < 150 Ω/km Inductance per unit length: 0.4 mh/km L 1 mh/km Capacitance per unit length: 45 nf/km C 200 nf/km (including the shield) Taking the shield into account, the capacitance per unit length is calculated as follows: C = C conductor/conductor x C conductor/shield if the bus line is isolated or C = C conductor/conductor + C conductor/ shield if the shield is connected to a pole of the Linking Device/Power Link. 9. The bus segment must be terminated at both ends of the line with a bus terminator. The fieldbus terminator must adhere to the following limits: 90 Ω R 100 Ω 0 μf C 2.2 μf 18 ABB

19 The Entity model The Entity model is based on the observation that the cable represents a concentrated inductance and capacitance. This has the result that, compared to the FISCO model, less electrical energy can be transmitted into the hazardous area. Typical values here are 10.6 V and 70 ma. Result Fewer stations can be operated on a fieldbus segment The line lengths that can be achieved are smaller than in the case of the FISCO model Points 1 to 9 listed in the section The FISCO model also apply to the Entity model, with the exception of point 5. According to the Entity model, the internal inductance of a field device must be 20 μh and the internal capacitance must be 5 nf. The prerequisite for being able to furnish evidence of intrinsic safety in accordance with the FISCO model is that the source providing the power supply here the Linking Device, Power Repeater, or Fieldbus Barrier and all fieldbus stations are certified in accordance with the FISCO model. In addition, the cable must meet the requirements of the FISCO model. In order to prove intrinsic safety in accordance with the Entity model, in addition to comparing the voltage, current, and power, it is also necessary to establish that the inductances and capacitances connected to the Fieldbus Barrier do not exceed the maximum permissible values Lo and Co. In general: Lo Lcable + _Li Co Ccable + _Ci ABB 19

20 The latest information about ABB can be found on the Internet at abb Automation Technologies Mannheim, Germany Phone: +49 (0) Fax: +49 (0) Automation Technologies Västerås, Sweden Phone: +46 (0) Fax: +46 (0) Automation Technologies Wickliffe, Ohio, USA Phone: Fax: BDD EN Copyright 2006 ABB. All rights reserved. The content is subject to change without prior notice. Pictures, diagrams, and other graphics in this document are simply provided for illustration and do not represent any product configurations or product functions. The user documentation supplied with the product is the sole source for descriptions of product functionality. Industrial IT, Aspect Objects, and all product names mentioned above in the form XXXXXX IT are registered or requested trademarks of ABB. All rights to trademarks reside with their respective owners.