B&R X20BB57 Compact-S PLC Bus Base Module

Product Overview

The X20BB57 (X20BB57) is a foundational bus module specifically engineered for the B&R X20 Compact-S PLC series. Functioning as the primary backplane, it provides the essential mechanical and electrical interface for the Compact-S CPU and its corresponding power supply modules. This module is designed to streamline system architecture by integrating dual communication interfaces—RS232 and CAN bus—directly into the base hardware. Ideal for space-constrained applications in mobile automation, specialized machinery, and distributed control systems, the X20BB57 ensures high-speed backplane communication while maintaining a robust 10 A power distribution capacity across the I/O segment.

Hardware Architecture and Interface Logic

The X20BB57 serves as the backbone of the Compact-S station, managing both power delivery and high-level communication protocols within a single hardware footprint.

• Integrated Communications: Equipped with one RS232 port and one CAN bus connection, facilitating direct peripheral integration without additional interface cards.

• Non-Isolated Design: Per the engineering specification (ID code 0xEB09), the Bus, CAN bus, and RS232 interfaces share a common potential. This design minimizes internal propagation delays and power consumption (0.55 W).

• Universal Mounting: Unlike many specialized bases, this module supports both horizontal and vertical mounting orientations, providing mechanical flexibility for shallow or tall control cabinets.

Technical Specifications

Technical FAQs

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

No, the X20BB57 is designed with the Bus, CAN bus, and RS232 interfaces not isolated from each other. In environments with significant potential differences or high electrical noise, engineers should use external isolation barriers or ensuring a common high-quality reference ground to prevent signal corruption.

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

For installations up to 2000 m above sea level, there are no limitations. For elevations exceeding 2000 m, you must apply a derating factor to the ambient temperature of 0.5 Celsius per 100 m to account for reduced air density and cooling efficiency.

What is the maximum current I can run through the I/O power supply contacts?

The module supports a permissible contact load of 10 A. This rating is critical when calculating the total current draw of all downstream I/O modules attached to the Compact-S backplane to prevent thermal damage to the bus contacts.

Field Engineering & Installation Guide

• Orientation-Based Thermal Limits: Note that the maximum operating temperature drops from 60 Celsius (horizontal) to 50 Celsius (vertical). In vertical installations, rising heat from lower modules can accumulate; ensure forced-air cooling is utilized if the cabinet density is high.

• Interface Wiring: Since the RS232 and CAN interfaces are not isolated, always use high-quality shielded cables. Connect the cable shields to the ground bar at the cabinet entry point to mitigate the risk of ground loops affecting the CPU logic via the X20BB57 backplane.

• ID Code Verification: During software commissioning in B&R Automation Studio, the hardware will report ID code 0xEB09. Ensure the hardware configuration in your project matches this ID exactly to enable full functionality of the CAN and RS232 drivers.

Engineering Advantages

The X20BB57 is a "hardened" backplane solution designed for reliability. Its wide operating temperature range (down to -25 Celsius) makes it suitable for outdoor control panels and cold-storage automation. By integrating the backplane and communication ports into a single unit, it reduces the number of physical connections, thereby increasing the Mean Time Between Failures (MTBF). The robust IP20 housing and the ability to withstand up to 95% non-condensing humidity ensure stable performance in the most demanding industrial climates.