ABB RB520

Description

Product Description

The ABB RB520 is a reliable and versatile digital output relay module from ABB’s extensive range of interface and control components. Designed primarily for use with ABB’s AC 500 (PM5xx) and other compatible PLC families, this module serves as a critical intermediary between the low-voltage logic signals of the controller and higher-power field actuators. Its core function is to provide safe, isolated, and amplified switching capability, allowing a PLC’s digital output to reliably control loads such as contactors, solenoid valves, motor starters, indicator lamps, and alarm devices. The ABB RB520 is engineered for easy DIN-rail mounting and features robust relay outputs capable of handling significant inductive and resistive loads. This module simplifies system design by offloading high-current switching from the PLC’s internal electronics, thereby enhancing system reliability and protecting the controller. The integration of the ABB RB520 is a standard practice for creating robust and maintainable control interfaces in industrial automation panels.

Product Parameters

• Module Family: ABB Relay Output Module.
• Module Type: Digital Output Relay Module (typically 2 or 4 changeover relay outputs).
• Output Configuration: Typically features Form C (SPDT – Single Pole Double Throw) relay contacts.
• Contact Rating: Rated for substantial switching loads (e.g., 5A at 250V AC or 30V DC).
• Coil Voltage: Designed to be driven by standard PLC digital output voltage, typically 24V DC.
• Isolation: Provides galvanic isolation between the PLC control circuit (coil) and the switched load circuit (contacts).
• Status Indicators: LED indicator for each channel to show when the relay is energized.
• Mounting: Standard 35mm DIN-rail mounting.
• Wiring: Screw terminal connections for easy installation.
• Dimensions: Compact, modular width (e.g., 22.5mm per 2-channel module).

Advantages and Features

• High Load Switching Capacity: The relay contacts can switch significantly higher currents and voltages than a standard transistor-based PLC output, enabling direct control of industrial actuators without additional interposing devices.
• Electrical Isolation: The built-in isolation protects the sensitive PLC electronics from voltage spikes, noise, and potential faults on the load side, which is crucial for system longevity.
• Clear Visual Feedback: Per-channel LED indicators provide immediate visual confirmation of the output command status, simplifying commissioning and troubleshooting.
• Flexible Contact Configuration: The Form C (SPDT) contacts allow for versatile wiring (normally open, normally closed, or break-before-make switching) to suit different application needs.
• Easy Installation and Replacement: The DIN-rail mounting and screw terminals facilitate quick installation and easy module replacement if necessary, minimizing downtime.

Application Cases in Application Fields

• Motor Control Panels: Used to start and stop motors via contactors, where the PLC output drives the ABB RB520 coil, which in turn switches the power to the contactor coil.
• HVAC Control Systems: Controls fan motors, damper actuators, and alarm horns in building management systems.
• Industrial Lighting Control: Switches banks of high-wattage industrial lighting fixtures.
• Pump Control Skids: Activates pump contactors and alarm indicators in water treatment or chemical dosing applications.
• Conveyor Systems: Controls motor starters for conveyor drives and sorting diverters.

Comparisons with Competing Products

• Vs. Siemens SIRIUS 3RH Contactor Relays: Siemens offers a similar range of interface relays. The ABB RB520 is directly comparable in function. The choice often comes down to brand preference for ancillary components, panel builder standards, and availability.
• Vs. PLC with High-Current Transistor Output Cards: Some PLCs offer high-current (e.g., 2A) transistor outputs. The ABB RB520 relay module offers higher current capacity, complete galvanic isolation, and the ability to switch AC loads directly, which transistor outputs cannot do.
• Vs. Solid-State Relays (SSRs): SSRs offer faster switching and longer life for very high cycle rates. The ABB RB520 electromechanical relay is better suited for lower switching frequencies, offers lower off-state leakage, and can handle a wider range of load types (AC/DC) with a single module. It is also typically more cost-effective for standard industrial switching.

Selection Suggestions and Precautions

1. Load Rating Verification: Always check the inrush current of the load (especially for inductive loads like contactors and solenoids). Ensure the relay’s contact rating exceeds both the inrush and steady-state current. Derating the relay for inductive loads is a common practice.
2. Use of Suppression Circuits: For inductive DC loads, always install a flyback diode (or RC snubber for AC loads) directly across the load to suppress voltage spikes generated when the relay opens. This protects the relay contacts and can significantly extend their lifespan.
3. Correct Coil Drive: Ensure the PLC output used to drive the ABB RB520 coil can supply the required coil current. Most 24V DC PLC outputs are sufficient, but always verify to avoid under-driving the coil.
4. Physical Separation of Wiring: Keep the low-voltage control wiring (to the coil) separate from the high-voltage load wiring (to the contacts) within the cabinet to maintain noise immunity and safety.
5. Consider Switching Frequency: Electromechanical relays like the ABB RB520 have a limited mechanical life (e.g., 1-10 million operations). For applications requiring very high-speed or frequent switching (multiple times per second), a solid-state relay (SSR) may be more appropriate.

ABB 57160001-GF PLC
DSAI146 DCS
SC520 ABB
3BSE003816R1 DCS
SC510 ABB DCS