Pepperl+Fuchs KFD2-ST3-Ex2 2-Channel Switch Amplifier

KFD2-ST3-Ex2 two-channel switch amplifier with active outputs

The KFD2-ST3-Ex2 is the two-channel, active-output member of the Pepperl+Fuchs K-System switch amplifier series. Two NAMUR sensor or dry-contact inputs from a hazardous area each switch one transistor output that is fed from the module supply, so a PLC or relay coil can be driven without an external voltage source on the output side.

In the part number, KFD2 is the 24 V DC isolated barrier line, ST3 the active-transistor switch amplifier generation 3 and Ex2 the two-channel version. Its passive-output counterpart is the KFD2-SOT3-Ex2, and the single-channel versions carry Ex1 in the name.

Seven Star LLC supplies this barrier in Oman and the GCC as an independent supplier based in Muscat.

Technical specifications of the KFD2-ST3-Ex2

How the active output of the KFD2-ST3-Ex2 behaves

Each input of the KFD2-ST3-Ex2 is monitored for the NAMUR current band and, if enabled, for wire break and short-circuit. The output transistors are supplied from the 24 V rail: when active, the output terminal sits at roughly the supply voltage minus 3 V at full 100 mA load, and when blocked it leaks no more than 10 µA. This allows direct drive of PLC inputs of the sinking type, small relays, or indicator lamps.

Faults are shown on LEDs following NAMUR NE44 and signalled to the shared error line of the Power Rail. DIP switches select the output action and line fault detection for each channel. Because the supply sets the output level, any supply sag below 19 V reduces the output voltage and can trip a sensitive PLC input, so confirm rail voltage during commissioning.

Where it fits and which parts are related

Use the KFD2-ST3-Ex2 when the receiving device has no supply of its own on that input, for instance a hard-wired alarm panel or a sinking PLC card. If the control card needs its own field voltage, move to the KFD2-SOT3-Ex2, and where a potential-free relay is required choose the KFD2-SR2-Ex2.W. All three share the 20 mm housing, so a layout change is easy.

Selection and ordering checklist

• Confirm that both field devices are NAMUR sensors or resistor-wired contacts.
• Check the receiving device can accept a supply-fed 24 V transistor output up to 100 mA.
• Confirm the rail voltage stays within 19 to 30 V DC.
• Check sensor Ex ia entity values against Uo, Io and Po.
• Confirm normal or reversed action per channel.
• Allow for the 0.9 W dissipation when sizing panel heat load.

Installation and maintenance of the KFD2-ST3-Ex2

Clip the module on a DIN rail, wire the field cables to the blue terminals and the output terminals to the control side, and set the DIP switches. During commissioning, simulate loop break and short, verify the LED indications, and check the output voltage under real load. Keep ventilation space around the module in warm cabinets, because the -20 to 60 °C range is measured at the module.

Hazardous-area data and isolation of the KFD2-ST3-Ex2

The input of the KFD2-ST3-Ex2 is intrinsically safe Ex ia with Uo 10.5 V, Io 17.1 mA and a linear Po of 45 mW, so the sensor and cable parameters must stay within those limits. The marking II 3(1)G Ex nA [ia Ga] IIC T4 Gc allows the module itself in Zone 2 while the sensor loop may reach Zone 0, and the dust and mining markings listed on the datasheet extend this to dust atmospheres and Group I. Certificate reference EXA 16 ATEX 0016 X carries special conditions of use that should be read from the certificate before installation.

Between input and output and between input and supply the module provides reinforced insulation for 300 Veff under IEC/EN 61010-1, and safe electrical isolation with a 375 V peak value under IEC/EN 60079-11 for the intrinsically safe circuit. The practical meaning is that a fault on the 24 V rail or on the output side cannot place hazardous energy on the field cable.

Typical applications in Oman and the GCC

The KFD2-ST3-Ex2 is used where small panels collect many NAMUR signals: well pad junction cabinets, pump station limit switches, LNG and gas plant packaged skids, and utilities in power and desalination plants. Two channels per slot reduce rack cost in large instrument rooms.

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Information to send with an RFQ

• Part number KFD2-ST3-Ex2 and quantity
• Sensor models and entity data
• Receiving device and input type
• Zone and gas group
• Rail or discrete supply
• Delivery location

Documents and quotation

The manufacturer datasheet for KFD2-ST3-Ex2 is attached on this page, so you can check wiring, approvals and dimensions before ordering. Send the exact part number, quantity and delivery location in Oman or the GCC and Seven Star LLC will reply with a quotation.

Seven Star LLC is an independent supplier in Muscat and is not the manufacturer; confirm availability, lead time and any project approval requirements in your RFQ.