Active Field Distributor AFD4

Active Field Distributor AFD4 RAILMOUNT

Active Field Distributor AFD8

Active Field Distributor AFD

Active field distributors (AFD) can be operated in environments in accordance with Division 2, Zone 2 or Zone 22. It is offered with the following models:

• AFD4, AFD4 RAILMOUNT and AFD4 FM with 4 spur line connections for 1 field device each
• AFD8 with 8 spur line connections for 1 field device each

An AFD4, AFD4 RAILMOUNT and AFD4 FM can therefore connect up to 4 field devices, and an AFD8 can connect up to 8 standard-compliant PROFIBUS PA‑field devices, via short-circuit proof spur line connections to a PA‑fieldbus segment (line/ring) with automatic bus termination.

The PA fieldbus segment can be connected to a single or redundant PROFIBUS DP via a PA router and can thus be seamlessly integrated into the SIMATIC PCS 7 process control system.

Up to 8 active field distributors AFD with a total of up to 31 connected field devices can be operated for each fieldbus segment. The number of field devices is also limited by the current consumption of the field devices. A maximum of 60 mA per spur line and a maximum of 1 A per segment is available for the field devices.

An AFD in a ring segment can be replaced during operation without resulting in failure of the segment.

For compliance with IP66 protection, it is necessary to protect unused spur line connections using plugs.

Active Field Distributor AFD8, open

Based on the AFD4, two product versions with different intentions were developed with the AFD4 RAILMOUNT and the AFD4 FM:

Specific product features of the AFD4 RAILMOUNT

The AFD4 RAILMOUNT is supplied without die-cast aluminum enclosure; it is a product model of the AFD4 active field distributor with flexible installation options. It can be installed on a DIN mounting rail into an enclosure of choice, for example, an enclosure made of stainless steel, die-cast aluminum or plastics.

Specific product features of the AFD4 FM

The AFD4 FM with cFMus approval is adapted to the special requirements for product models of the AFD4 active field distributor in the USA and Canada. The AFD4 FM features threaded plugs ex factory, because the cable glands of the AFD4 do not conform to the requirements of cFMus.

The threaded plugs for connecting the main and spur lines must be replaced by the cable glands and cables listed by UL or CSA. This must conform to the US National Electrical Code (NEC) and Canadian Electrical Code (CEC). The user is responsible for the selection and ordering.

Available suppliers for suitable cable glands:

• Cooper Capri SAS
• CMP products

Due to the larger bushing for the main line (M20 instead of M16), sheathed main line cables can also be used for AFD4 FM.

The relevant requirements of the US National Electrical Code (ANSI/NFPA‑70 NEC) must be met for the installation of the AFD4 FM.

AFDiSD active field distributor

AFDiSD active field distributor

The AFDiSD (Active Field Distributor intrinsically Safe with optional extended PROFIBUS PA diagnostics) PROFIBUS PA field distributor can be operated in environments in accordance with Ex zone 1/21 and 2/22. It is a compatible replacement for AFDiS.

AFDiSDs can integrate up to 6 intrinsically-safe PA field devices in a PA fieldbus segment (line/ring) via its intrinsically-safe, short-circuit proof spur line connections. Instead of the spur line, it is also possible to use a subsegment for 3 to 4 devices with a max. length of 500 m at connection S1. The spur lines with Ex [ia] type of protection as well as the subsegment can be routed into Zone 0/20.

Up to 5 AFDiSD active field distributors with a total of up to 31 field devices can be operated in a fieldbus segment. A limitation of 5 active field distributors is also mandatory for mixed operation of AFD and AFDiSD (extended PA fieldbus diagnostics in mixed operation).

The number of field devices per segment additionally depends on the current consumption of the devices and the cable lengths used. A current of 1 A is available for all field devices and the active field distributors of the segment.

With its integrated repeater function, AFDiSDs have the following advantages compared to the AFD:

• Spur line lengths are independent of the total number of spur lines in the bus segment
• Spur line lengths need not be be taken into account when determining the total length of the bus segment

In environments in accordance with Ex zone 2/22 or in non-hazardous areas, an AFDiSD in a ring segment can be replaced during operation without failure of the segment.

For compliance with IP66 protection, it is necessary to protect unused spur line connections using plugs.

Enhanced fieldbus diagnostics with AFDiSD in PROFIBUS PA

AFDiSD diagnostics are limited to short-circuits, loss of redundancy, detection of chatter, and failure of field devices. In addition, the extended fieldbus diagnostics, which can be activated per mode selector, enables comprehensive diagnostics of the entire PROFIBUS PA segment.

This includes, among others, the detection, recording and monitoring of:

• Topology (DP/PA coupler, AFDiSD)
• Voltage and currents on the main and spur lines
• Signal and noise levels
• Capacitive unbalance to shield of main line

Configuration errors or defects can thus be rapidly detected and eliminated.

However, a prerequisite for application of the extended fieldbus diagnostics is that all active field distributors of the segment as well as the components of the PA link support this functionality. The following components satisfy this requirement:

• Active Field Distributor AFDiSD, Article No. 6ES7655-5DX60-1BB0
• IM 153‑2 High Feature Outdoor interface module, Article No. 6ES7153-2BA70-0XB0
• DP/PA coupler FDC 157, Article No. 6ES7157-0AC85-0XA0

The interface module creates a topology model of the connected bus segment, and maps its status information. The DP/PA coupler and the locally installed active field distributor AFDiSD provide the interface module with the physical data of the bus segment for this purpose, as well as information on the status of the connected lines. The information provided by the interface module can be displayed on the PCS 7 Maintenance Station and evaluated by SIMATIC PDM.

When delivered from the factory, the enhanced fieldbus diagnostics is not activated in the AFDiSD. In this state, the functionality of the AFDiSD is equivalent to that of the AFDiS predecessor type.

Active Field Splitter AFS

The active field splitter (AFS) connects a PA line segment with a redundant coupler pair in the PA router PA Link. The AFS interconnects the line segment with the respective active coupler.

The PA line segment can be connected to the AFS via one or two (center feed) identical Y-connectors out of a total of 4. For the center feed, the line segment is connected via the two Y-connectors (bus termination switch on both FDC 157 couplers set to "OFF").

For compliance with IP66 protection, it is necessary to close unused connections using sealing plugs.

AFS: Active Field Distributor for PROFIBUS PA