Pepperl+Fuchs KFD2-STC4-Ex1.H K-System SMART Transmitter Power Supply

Description

The KFD2-STC4-Ex1.H is a 1-channel isolated barrier designed for intrinsic safety applications. This device supplies 2-wire and 3-wire SMART transmitters with a higher output voltage in hazardous areas, and it can also be configured for use with 2-wire SMART current sources. It transfers the analog input signal to the safe area as an isolated current value. Digital signals can be superimposed on the loop in either the hazardous or safe area to enable robust bi-directional communication. The module maintains galvanic isolation across the system to preserve loop integrity in demanding industrial process control networks.

Features

• Intrinsic Safety Isolation: Provides reliable signal transfer between hazardous zone field devices and safe area control systems.
• High Field Voltage Support: Delivers an available voltage of >= 17.6 V DC at 20 mA to adequately power field instrumentation.
• Multi-Protocol SMART Support: Fully compatible with digital communication protocols, including HART, BRAIN, and Foxboro.
• Integrated Loop Resistance: Features an internal 250 Ohm resistor between terminals 8 and 9 that can be selected if the loop's HART communication resistance is insufficient.
• Integrated Test Points: Built-in test sockets are directly integrated into the terminals to simplify connection of HART communicators.
• Functional Safety Rating: Certified up to SIL2 compliance according to IEC 61508 standards.

Applications

• Petrochemical and Refining: Powering and isolating field transmitters located in explosive atmospheres like Zone 0, Zone 1, and Zone 2 environments.
• Chemical Processing: Bi-directional data extraction from smart field instrumentation back to a distributed control system (DCS) or safety instrumented system (SIS).
• Water and Wastewater: Interfacing with liquid and level measurement transmitters over long-distance cable runs utilizing standard 4-20 mA control loops.

Technical Specifications

Connections/Interfaces

Installation Guidelines

• DIN Rail Installation: Snap the module vertically onto a standard 35 mm DIN mounting rail ensuring the locking tabs engage securely.
• Power Rail Integration: When using the optional Power Rail system, align the module's bottom contacts with the rail insert before clicking it down; do not wire power to individual terminals if the rail is energized.
• Polarity Verification: Double-check terminal wiring configuration diagrams for 1+, 2-, 14+, and 15- prior to switching on the loop power source to prevent hardware faults.
• Hazardous Area Precautions: Maintain safe physical separation between the blue hazardous intrinsically safe terminal connections and the green safe area connections.
• Communication Termination: Bridge terminals 8 and 9 if the target system requires the insertion of the internal 250 Ohm resistor to stabilize HART protocol interactions.

Compliance and Certifications

• EC-Type Examination Certificate: BAS 99 ATEX 7060 
• ATEX Group, Category, Protection Type: II (1)G [Ex ia Ga] IIC, II (1)D [Ex ia Da] IIIC 
• Zone 2 Conformity Statement: TÜV 99 ATEX 1499 X; II 3G Ex nA II T4 [device in zone 2] 
• Mining Certification: DMT 01 ATEX E 133; (M1) [Ex ia] I 
• IECEx Approval: IECEx BAS 04.0016; [Ex ia Ga] IIC, [Ex ia Da] IIIC, [Ex ia Ma] I 
• UL Approval: 116-0173 (cULus) 
• Functional Safety Standards: Up to SIL2 according to IEC 61508 
• Electromagnetic Compatibility: EN 61326-1:2006, NE 21:2006 

FAQ

What is the primary function of this module?

The device functions as an isolated barrier that provides power to transmitters in hazardous zones and transfers isolated analog signals back to a safe area control system.

Can this barrier be used with non-HART devices?

Yes, it functions perfectly with standard 0/4 to 20 mA analog instruments even if digital modulation protocols are not deployed.

How does the internal 250 Ohm resistor assist with communication?

If the loop impedance of the safe area control system is too low for a HART communicator to decode data, using terminal 9 adds the integrated resistor into the circuit.

What power supply range does the device accept?

The module operates reliably on any input supply voltage between 20 V DC and 35 V DC.

Does this isolated barrier require a direct terminal connection for power?

Power can be supplied either directly through terminals 14+ and 15- or smoothly via a compatible Power Rail unit.

Can it support a 3-wire transmitter configuration?

Yes, the hardware accommodates both 2-wire and 3-wire SMART transmitters as well as 2-wire current sources.

What do the green and blue terminals signify?

The blue terminals are dedicated to fields located within hazardous, intrinsically safe zones, while the green terminals are intended for safe area or control-side wiring.

What is the response speed of the analog transmission channel?

The device features a settling time of 200 microseconds along with a rise and fall time specification of 20 microseconds.

How many channels does this module support?

This model is a dedicated single-channel interface unit.

What should I check if the front panel LED is off?

An unlit green LED indicates a power supply failure, requiring verification of the 24 V DC power rail or terminal connections.

What is the maximum allowed load resistance on the output side?

The safe area current loop supports load impedances ranging from 0 Ohm up to a maximum limit of 800 Ohm.

Are there integrated testing connections available on the unit?

Yes, specialized test sockets designed to fit standard HART communicator leads are constructed right into the removable terminals.

Can this device pass digital parameters backwards and forwards?

The circuit layout allows digital communication signals to superimpose on the analog current loop and pass bi-directionally.