B&R X20BB57 X20 Series Compact-S PLC Base Bus Module

Product Overview

The X20BB57 (X20BB57) serves as the fundamental hardware foundation for the B&R X20 Compact-S PLC series. This specialized bus module acts as the backplane for both the Compact-S PLC processor and its associated power supply module, facilitating seamless communication and power distribution. Designed to maximize panel space without sacrificing connectivity, the X20BB57 includes integrated physical interfaces for 1x RS232 and 1x CAN bus. Engineered for versatile industrial deployment, it supports a wide operating temperature range from -25 to 60 deg C, making it a reliable backbone for decentralized control systems in manufacturing, energy management, and mobile automation.

Technical Configuration

The X20BB57 architecture is optimized for low-profile integration, with a logic-side power consumption of just 0.55 W. It provides a robust electrical infrastructure capable of handling a 10 A contact load for I/O power supply distribution at a nominal 24 VDC. A key technical characteristic of this module is that the internal bus, CAN bus, and RS232 interfaces are not electrically isolated from each other; they share a common potential, which simplifies grounding strategies in localized control nodes. The module is fully rated for high-altitude operation, supporting installations up to 2000 m without de-rating, and is protected to IP20 standards for installation in standard industrial enclosures.

Technical Specifications

Technical FAQs

Does the X20BB57 provide isolation between the CAN bus and RS232 ports?

No, according to the technical specifications, the internal bus, CAN bus, and RS232 interfaces are not isolated from one another. Engineers should ensure that connected devices share a compatible ground potential to avoid ground loops or communication errors.

How does installation altitude affect the performance of this bus module?

For installations between 0 and 2000 m above sea level, there is no performance limitation. For elevations exceeding 2000 m, the maximum ambient operating temperature must be reduced by 0.5 deg C for every additional 100 m of elevation to account for reduced air density and cooling efficiency.

Is it possible to mount the X20BB57 in a vertical orientation?

Yes, the module supports both horizontal and vertical mounting. However, vertical mounting reduces the maximum permissible operating temperature from 60 deg C to 50 deg C to ensure adequate passive heat dissipation through the module's ventilation slots.

Engineering & Installation Guide

• Grounding and Interface Protection: Since the RS232 and CAN bus interfaces share a common potential, it is critical to use shielded cables for all communication lines. The shield should be connected to a low-impedance functional earth (FE) at the entry point of the control cabinet to protect the non-isolated circuitry from external electromagnetic interference (EMI).

• Thermal Planning for High-Altitude Use: When deploying the X20BB57 in high-altitude environments (e.g., mountain-top wind turbines or mining operations above 2000 m), calculate the temperature de-rating carefully. If the local environment reaches 40 deg C at 4000 m, the 10 deg C de-rating (0.5 deg C * 20 segments of 100 m) means the module is effectively operating near its upper thermal limit.

• Bus Connection Integrity: Ensure the Compact-S PLC and power supply modules are fully seated and the locking mechanisms are engaged. The X20BB57 manages the 10 A I/O power rail; any loose connection can lead to localized heating or intermittent power loss to downstream I/O modules connected to the X2X Link.