Pepperl+Fuchs KFD2 Series Modules KFD2-VM-EX1.35 Solenoid Driver

Technical Dossier

Product Details And Specifications

Pepperl+Fuchs KFD2 Series Technical Notes

The Pepperl+Fuchs KFD2 series is a DIN-rail-mounted, 24 V DC loop-powered signal conditioning platform engineered for intrinsically safe (Ex ia) and non-incendive field device interfaces in Zone 1/2 and Division 1/2 hazardous areas. Deployed across global heavy industry — including petrochemical complexes, offshore platforms, nuclear power stations, and crude oil refineries — the KFD2 range serves as the backbone of field-to-DCS signal isolation in facilities where SIL 2/3 functional safety compliance is mandatory. Its modular, single-channel architecture allows granular replacement without system-wide shutdown, a critical operational advantage in continuous-process environments. The series is certified to ATEX, IECEx, FM, and CSA standards, making it a globally accepted solution for hazardous-area signal conditioning.

The Evolution of KFD2 Architecture

The KFD2 platform succeeded the earlier KFD (first generation) and KFA series, which relied on bulkier transformer-isolated designs with higher power consumption. The KFD2 generation introduced compact 20 mm single-channel housings, integrated power rail bus (Power Rail concept), and standardized terminal assignments that simplified engineering and commissioning. Early KFD2 modules used discrete analog circuitry; later revisions incorporated microcontroller-based signal processing, enabling HART transparency — a feature critical for asset management systems such as Emerson AMS and Honeywell FDM. The series reached maturity in the 2000s and has since entered a stable maintenance phase. Pepperl+Fuchs has introduced the KFD3 and RN series as next-generation successors, but KFD2 remains the dominant installed base across legacy DCS platforms including Yokogawa CENTUM, ABB 800xA, Honeywell Experion, and Emerson DeltaV. Replacement and lifecycle extension support for KFD2 modules is therefore a long-term industrial requirement extending well beyond 2030.

KFD2 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly deployed modules within the KFD2 series, organized by functional category. Each module occupies a single 20 mm slot on the Power Rail and operates from the 24 V DC bus.

Solenoid / Valve Drivers (DO)

• KFD2-VM-EX1.35: Single-channel solenoid driver, Ex ia IIC, 24 V DC output, for Zone 1 valve actuators
• KFD2-SL-EX1.LK: Single-channel solenoid driver with line fault detection, loop-powered, ATEX Zone 1
• KFD2-SL2-EX1.LK: Dual-channel solenoid driver with independent line monitoring per channel
• KFD2-SR2-EX2.2S: Dual-channel switch amplifier with relay output, for solenoid and on/off valve control

Analog Input Isolators (AI)

• KFD2-STC4-EX1.4O: 4–20 mA transmitter power supply and isolator, single-channel, HART transparent
• KFD2-STC4-EX2.4O: Dual-channel 4–20 mA transmitter supply with HART pass-through
• KFD2-CR-EX1.30P: Single-channel current repeater, 4–20 mA, galvanic isolation, passive input
• KFD2-UT2-EX2: Universal temperature converter, dual-channel, supports TC/RTD/mV/Ω inputs
• KFD2-VR-EX1.26: Voltage repeater, single-channel, 0–10 V DC signal conditioning

Digital Input Isolators (DI)

• KFD2-SR2-EX2.2S: Dual-channel switch amplifier, SPDT relay output, for proximity and limit switches
• KFD2-SR2-EX2.2W: Dual-channel switch amplifier with wire-break detection, relay output
• KFD2-DWB-EX2.D: Dual-channel namur/dry contact input, transistor output, for high-speed switching
• KFD2-GU-EX1.D: Single-channel NAMUR sensor interface, transistor output, Zone 0 capable

Analog Output Isolators (AO)

• KFD2-SCD2-EX1.LK: Single-channel current driver, 4–20 mA output to field, loop-powered
• KFD2-SCD2-EX2.LK: Dual-channel current driver, 4–20 mA, for I/P converters and control valves
• KFD2-WAC2-EX1.D: Single-channel frequency/pulse converter with analog output

Power Supply / Bus Modules

• KFD2-PWR-EX1.D: Power Rail segment coupler, 24 V DC, feeds up to 20 KFD2 modules per segment
• KFA6-STR-1.24.500: Power supply unit, 24 V DC / 500 mA, for standalone KFD2 installations without Power Rail

Quality Control for the KFD2 Range

KFD2 modules incorporate multi-layer PCBs with conformal coating, precision analog front-ends, and optocoupler-based galvanic isolation barriers rated to 500 V AC. DriveKNMS applies a structured test protocol to all KFD2 units prior to dispatch. Each module undergoes functional loop simulation: for AI modules, a calibrated 4–20 mA source verifies linearity and offset at 0%, 25%, 50%, 75%, and 100% of span. For DO/solenoid driver modules — including the KFD2-VM-EX1.35 — output switching voltage, current limiting behavior, and line fault detection thresholds are verified against OEM datasheet specifications. HART communication transparency is validated using a HART communicator on applicable AI/AO modules. Isolation resistance between field-side and system-side terminals is measured at 500 V DC. Modules failing any parameter are quarantined and not released for sale.