Product Overview

The Allen‑Bradley 1797‑PS1E​ is a dedicated intrinsically safe (IS) power supply unit engineered for Rockwell Automation’s FLEX Ex I/O system (1797 series), which is specifically designed to operate in classified hazardous areas such as petrochemical plants, offshore platforms, pharmaceutical process suites, and grain‑handling facilities where flammable gases, vapors, or combustible dusts may be present. Unlike a conventional panel‑mount DC power supply, the 1797‑PS1E​ incorporates certified energy‑limiting circuits that restrict voltage, current, and power at its outputs to levels proven incapable of igniting an explosive atmosphere — thereby functioning simultaneously as both a power source and an intrinsic safety barrier (Zener‑barrier alternative) for connected 1797 FLEX Ex I/O modules and their associated field instruments (transmitters, solenoid valves with IS pilot, proximity switches, etc.).Accepting a wide‑range AC mains input of 85–253 VAC at 47–63 Hz, the Allen‑Bradley 1797‑PS1E​ produces four independently galvanically isolated intrinsically safe output channels, each delivering up to 9.5 VDC at a maximum of 1 A (typical usable power ≈ 8.5 W per channel), with Uo ≤ 9.5 V, Io ≤ 1 A, and Po ≤ 8.5 W per EN 60079‑11 intrinsic safety parameter limits. The unit is housed in a heavy‑duty flameproof (Ex d) cast‑aluminum enclosure with an IP65 / Type 4X (indoor use) ingress‑protection rating, suitable for direct wall‑ or panel‑mounting in Zone 1 (gas) / Zone 21 (dust) hazardous locations per ATEX, IECEx, and cCSAus certifications. Cable entry is via included M20 and M16 threaded glands or optional conduits. The 1797‑PS1E​ is the foundational component of any 1797 FLEX Ex node: it powers the bus interface module (e.g., 1797‑BIC​ / 1797‑BICNT) and all associated Ex‑certified I/O modules on the same local 1797 rack segment through the IS energy‑limited outputs.By integrating intrinsic safety generation and galvanic isolation into a single, certified Ex‑d enclosure, the Allen‑Bradley 1797‑PS1E​ eliminates the need for separate Zener diode safety barriers, associated barrier racks, and non‑IS cabling runs back to a safe‑area power panel — significantly reducing installation cost, cabinet space, and system complexity in hazardous‑area automation projects while maintaining full compliance with international explosion‑protection standards.

Technical Specifications

Main Features and Advantages

Integrated intrinsic safety — no external barriers required: Each of the four output channels on the 1797‑PS1E​ is a certified intrinsically safe source per IEC 60079‑11 (Entity Concept). This means field wiring from the IS outputs to 1797 FLEX Ex I/O modules and on to IS‑rated field instruments (e.g., 2‑wire 4–20 mA transmitters, Namur proximity switches) does not require separate Zener barriers or galvanic isolators. The energy‑limiting circuitry caps open‑circuit voltage at ≤ 9.5 V and short‑circuit current at ≤ 1 A, ensuring that even under fault conditions (short or open) in the field wiring the energy available cannot ignite the most easily ignitable gas group (IIC) mixtures — a key advantage in reducing panel footprint and wiring cost compared to traditional barrier‑based IS designs.Four‑way galvanic isolation between outputs: The four IS output circuits are mutually isolated from each other and from the AC input / ground. This prevents a fault on one IS loop (e.g., a shorted field cable on Channel 2) from affecting the voltage or integrity of other channels, and allows each output to feed an independent 1797 FLEX Ex I/O segment or a separate group of field instruments. For larger FLEX Ex racks, multiple 1797‑PS1E​ units can be deployed, or a single unit can power both the FLEX Ex bus interface module (1797‑BIC/‑BICNT) on Ch‑1 and distribute the remaining three channels to power local analog/digital Ex I/O modules.Flameproof Ex d enclosure for direct hazardous‑area installation: Housed in a robust cast‑aluminum flameproof enclosure with machined flamepaths and certified for Zone 1 / Class I Div 1 installation, the 1797‑PS1E​ can be mounted directly in the hazardous area — on a skid, near a tank farm, or on a process unit — rather than in a costly purged/pressurized enclosure or a distant safe‑area panel. The IP65 rating with properly installed M20/M16 cable glands protects against dust and water ingress in outdoor or wash‑down environments common to refineries and chemical plants.Wide AC input range and global applicability: The 85–253 VAC input span accommodates both 120 VAC (North America) and 230 VAC (Europe/Asia) mains without jumpers or selector switches, simplifying spare‑parts logistics for multinational OEMs and EPCs. Internal over‑temperature, over‑current, and short‑circuit protection on the AC side ensures robustness against supply anomalies.LED status and removable terminal blocks: Front‑panel LEDs provide at‑a‑glance indication of AC power presence and IS output channel health. Removable spring‑clamp or screw terminal blocks (depending on sub‑revision) allow pre‑wiring offline and quick module exchange if service is required — a practical benefit during maintenance outages where minimizing exposure time in the hazardous area is desirable. The 1797‑PS1E​ supports removal/insertion under power (RIUP) within system constraints, though standard hazardous‑area hot‑work policies should be observed.