BECKHOFF EL2788 EL Series Solid State Relay Terminal

Product Overview

The EL2788 (EL2788) is a high-density, 8-channel solid state relay (SSR) output terminal from the Beckhoff EL series, designed to replace conventional mechanical relays in high-frequency switching applications. By utilizing semiconductor-based switching, this module provides an virtually unlimited operational lifespan and silent operation, making it ideal for the rapid toggling of ohmic and inductive loads in industrial automation. Housed in a compact High Density (HD) package, the EL2788 allows for significant space savings in control cabinets while delivering reliable 2 A per-channel switching for loads up to 30 V AC or 48 V DC.

Technical Configuration

The EL2788 architecture is optimized for performance and longevity, featuring an extremely low on-resistance (typ. 0.03 Ohm) that minimizes power dissipation and thermal buildup within the terminal housing. While the module supports a continuous current of 2 A per channel, the aggregate current for the entire module is limited to 10 A. It features a robust isolation barrier of 500 V between the E-bus and field potential. Engineers should note that this terminal is not inherently short-circuit proof; it relies on the peak current handling capacity (up to 50 A for 10 ms) and appropriate external fusing to protect the SSR outputs from overcurrent conditions.

Technical Specifications

FAQs

Why choose the EL2788 over a mechanical relay terminal?

The EL2788 uses semiconductor-based switching, which eliminates mechanical contact wear, pitting, and bounce. This results in faster switching cycles, silent operation, and a significantly longer MTBF (Mean Time Between Failures) in high-frequency applications.

What measures should I take to prevent short-circuit damage?

The EL2788 is not short-circuit proof. You must install appropriate external fuses for each channel or for the power supply contact group to protect the SSR output stage from surge currents that exceed the peak rating of 50 A (100 ms).

Can this terminal switch inductive loads?

Yes, it is designed for ohmic and inductive loads. When switching highly inductive loads (like large contactors or solenoid valves), ensure that external flyback diodes or RC snubbers are used to protect the SSR against voltage transients that exceed the 80 V breakdown voltage.

Installation and Operational Recommendations

• Thermal Load Management: Given the 8-channel high-density design, heat dissipation is critical. Ensure the module is mounted in a well-ventilated cabinet. If all 8 channels are switching at high duty cycles, consider leaving a small gap between the EL2788 and other heat-generating terminals to maintain the rated operating temperature.
• Wiring Integrity: The spring-actuated terminals are designed for solid and flexible wires. When using flexible conductors, always use ferrules to prevent fraying and ensure a secure, low-resistance connection that can handle the full 2 A current load without localized heating.
• Fusing Strategy: Because the SSR outputs lack internal current-limiting protection against short circuits, prioritize the use of fast-acting fuses that trip well before the 50 A peak current threshold is reached. This is the most effective strategy to ensure the longevity of the EL2788 in your control system.