AB | 1771-P4R | Power Supply | 1771 PLC-5 Series

Allen-Bradley 1771-P4R Redundant Power Supply – 1771 PLC-5 Series

When a power supply fails mid-shift on a continuous process line — a paper mill, a chemical reactor, an automotive body weld cell — the consequences are not simply a production pause. Uncontrolled shutdowns trigger safety interlocks, corrupt in-progress batch records, and in the worst cases damage downstream equipment that takes weeks to replace. The Allen-Bradley 1771-P4R was engineered specifically to eliminate that single point of failure. Its redundant output architecture keeps the 1771 I/O chassis energized even when one supply path degrades, giving maintenance teams a window to swap the faulty unit without halting the process.

Within the 1771 PLC-5 ecosystem, the 1771-P4R occupies the high-availability tier. Where the standard 1771-P4 provides a single regulated DC output for general-purpose I/O chassis, the 1771-P4R adds a parallel redundant supply path and a fault-detection relay output that can signal the PLC-5 processor or an external alarm panel. Rockwell Automation introduced this module to address the reliability requirements of continuous-process industries, and it remains the reference design for 1771 chassis redundancy in legacy plant infrastructure worldwide.

Technical Specifications

Electrical

• Input Voltage: 120/240 V AC, 47–63 Hz, single-phase
• Output Voltage: +5 V DC (logic bus), +24 V DC (field power, where applicable)
• Output Current: 10 A continuous on the 5 V logic bus
• Redundant Supply Paths: 2 (load-sharing, automatic failover)
• Fault Relay Output: Form-C dry contact, rated 2 A @ 30 V DC / 0.5 A @ 125 V AC
• Inrush Current: <30 A peak at cold start

Mechanical

• Form Factor: Single-slot 1771 I/O chassis power supply bay
• Connector: Proprietary 1771 backplane edge connector
• Weight: approx. 900 g
• Dimensions: Per 1771 chassis power supply bay standard

Environmental

• Operating Temperature: 0 °C to +60 °C
• Storage Temperature: −40 °C to +85 °C
• Relative Humidity: 5–95 % non-condensing
• Vibration: 2 G, 10–500 Hz (IEC 60068-2-6)
• Shock: 30 G, 11 ms half-sine (IEC 60068-2-27)

Certifications & Standards

• UL Listed, CE Marked
• Compliant with IEC 61131-2 (Programmable Controllers — Equipment Requirements and Tests)

Key Features & Benefits

• Redundant load-sharing architecture — Two supply paths share the load equally under normal operation; if one path fails, the other assumes full load within one AC cycle (<20 ms), preventing any logic-bus dropout that would reset the PLC-5 processor.
• Fault relay output for supervisory integration — The Form-C relay contact can wire directly into a PLC-5 discrete input or a DCS alarm card, enabling automated fault logging and maintenance dispatch without operator intervention.
• 10 A continuous logic-bus capacity — Supports fully populated 1771 I/O chassis configurations (up to 16 I/O modules) without derating, eliminating the need for chassis load calculations in most standard applications.
• Wide AC input range (120/240 V, 47–63 Hz) — A single SKU covers both North American 120 V and international 240 V plant utilities, reducing spare-parts inventory complexity for multi-site operations.
• IEC 61131-2 compliance — Meets the environmental and electrical immunity requirements of the international PLC equipment standard, confirming suitability for industrial environments with conducted and radiated EMI.
• Hot-swap compatible in redundant chassis configurations — When paired with a second 1771-P4R in a dual-supply chassis bay, the faulted unit can be replaced under power, achieving zero-downtime maintenance aligned with IEC 60204-1 safe-maintenance principles.

Industry & Equipment Applications

• Oil & Gas — Upstream/Midstream: Compressor station control panels, pipeline SCADA RTU chassis, and wellhead safety shutdown systems where unplanned de-energization triggers emergency blowdown sequences.
• Pulp & Paper: Continuous digester control, paper machine drive coordination, and broke handling conveyors — processes where a PLC reset causes web breaks and hours of re-threading downtime.
• Automotive Body-in-White: Resistance spot-weld cell controllers, transfer line sequencers, and paint-shop conveyor PLCs operating on takt-time cycles where any unplanned stop propagates across the entire line.
• Water & Wastewater: Lift station pump controllers, SCADA-connected treatment plant I/O chassis, and chlorination dosing systems subject to utility power fluctuations.
• Food & Beverage: CIP (Clean-In-Place) sequence controllers, pasteurizer temperature control loops, and filling-line PLCs operating under FDA 21 CFR Part 11 audit requirements.
• Mining & Minerals Processing: Conveyor drive control panels, crusher sequencing systems, and flotation cell automation in remote sites where spare-parts lead times can exceed two weeks.

System Integration & Compatible Parts

Upstream (Chassis & Processors):

• 1771-A1B, 1771-A2B, 1771-A3B, 1771-A4B — 1771 I/O chassis (4, 8, 12, 16 slot)
• 1785-L20B, 1785-L40B, 1785-L80B — PLC-5 processors that reside in the same chassis

Downstream (I/O Modules):

• 1771-IAD, 1771-OAD — AC discrete input/output modules
• 1771-IFE, 1771-OFE — Analog input/output modules
• 1771-IXHR — Thermocouple/RTD input module

Equivalent / Replacement Considerations:

• 1771-P4 — Non-redundant variant; direct physical fit but no fault relay or redundant path. Acceptable only in non-critical applications where process downtime is tolerable.
• 1771-P7 — Higher-current (15 A) variant for fully populated chassis with high-density analog modules; not a drop-in replacement without verifying chassis bay compatibility.

Note: Always verify chassis bay type and slot configuration before substituting power supply variants. Consult Rockwell Automation publication 1771-UM006 for chassis power budgeting.

Our Quality Assurance Process

1. Visual & Physical Inspection: Each unit is examined for board-level damage, burnt components, corroded connectors, and missing hardware. Units with any physical anomaly are quarantined and not listed for sale.
2. Powered Functional Test: The module is energized on a 1771 chassis test bench. Output voltages (+5 V DC, +24 V DC where applicable) are measured under load and compared against Rockwell Automation factory specifications. Fault relay operation is verified by simulating a supply-path fault.
3. Burn-In & Thermal Soak: Units are operated at elevated ambient temperature (45 °C) for a minimum of 4 hours to screen for latent component failures before shipment.
4. Documentation & Traceability: Test results are logged against the unit serial number. Available documentation upon request includes: functional test report, inspection checklist, and certificate of conformance. Rockwell Automation original manuals can be provided in PDF format.

How to Order

1. Submit an Enquiry: Use the contact form on this page or email support@konmask.com with your required quantity, delivery timeline, and destination country.
2. Receive a Quotation: Our technical team reviews stock availability and condition grade, then issues a formal quotation — typically within 24 hours on business days.
3. Confirm & Ship: Upon order confirmation and payment, the unit is re-inspected, securely packaged with anti-static and foam protection, and dispatched with full tracking. Export documentation (commercial invoice, packing list) is included as standard.

Why Choose Konmask.com?

• Specialist focus on industrial automation components — We stock PLC, DCS, servo drive, and HMI parts from Allen-Bradley, Siemens, ABB, Schneider, and other major automation brands. This is not a general electronics distributor; it is a purpose-built industrial parts source.
• Every unit functionally tested before listing — We do not list parts as “untested” or “as-is.” If a unit cannot pass our bench test, it is not offered for sale.
• Technical pre-sales support — Our team can advise on compatibility, substitution risks, and integration requirements before you commit to a purchase. We speak the language of the control room, not just the warehouse.
• Global export experience — We ship to over 50 countries with full commercial documentation, EAR99 classification support, and experience navigating import requirements in Southeast Asia, the Middle East, and Europe.
• 24-hour enquiry response commitment — Time-critical plant shutdowns cannot wait. We prioritize urgent enquiries and maintain stock visibility across our supplier network to source parts quickly when our own inventory is depleted.

Frequently Asked Questions

Q: Is the Allen-Bradley 1771-P4R compatible with all 1771 I/O chassis sizes?
A: The 1771-P4R fits the dedicated power supply bay present on all standard 1771 I/O chassis (1771-A1B through 1771-A4B). It is not compatible with the 1771-A1 or 1771-A2 chassis variants that use an older power supply form factor. Always confirm your chassis catalog number before ordering.

Q: Can I use a 1771-P4R to replace a failed 1771-P4 in a non-redundant chassis installation?
A: Yes. The 1771-P4R is backward-compatible with single-supply chassis installations. The fault relay output can be left unwired without affecting normal operation. The redundant supply path simply operates as a hot standby, providing an upgrade in reliability at no configuration cost.

Q: What is the typical lead time for a tested 1771-P4R power supply module from Konmask.com?
A: For units in current stock, we typically ship within 2–3 business days of order confirmation. For sourced units (not in immediate stock), lead time is quoted individually based on supplier availability — usually 5–15 business days. Urgent plant-down situations are handled on a priority basis; please indicate urgency in your enquiry.

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