GE Fanuc 90-70: Can IC697CHS790 & CHS750 Extend In Series?

Industrial PLC Backplane Expansion: Can IC697CHS790 & CHS750 Extend In Series?

Industrial automation engineers often need more I/O capacity. The core question: can the IC697CHS790 and IC697CHS750 backplanes work together in a series? This article provides a definitive, expert-driven answer.

Understanding The GE Fanuc 90-70 Backplane Family

Core Components For PLC And DCS Architectures

GE Fanuc’s 90-70 series remains a reliable choice for factory automation. Two prominent backplanes are the IC697CHS790 and the IC697CHS750. Many control systems rely on these passive backplanes. They distribute power and data between modules.

The CHS790 offers a 9-slot configuration. The CHS750 provides a 5-slot alternative. These backplanes support CPUs, I/O, and communication modules. However, not all backplanes allow series linking.

Can You Perform Series Expansion Between CHS790 And CHS750?

Technical Reality Of Backplane Extension In Industrial Control

The short answer is no. You cannot directly extend the CHS790 and CHS750 in a series. These backplanes lack built-in expansion connectors for daisy-chaining. Each backplane forms an independent passive bus segment.

To increase chassis count, you need a bus controller or extender module. For example, the IC697BEM731 works as a bus expansion module. Without such active components, series expansion fails. This design maintains signal integrity in large-scale automation.

Therefore, do not attempt to physically connect these two backplanes end-to-end. The system will not recognize additional slots. Use approved GE Fanuc expansion kits instead.

Author’s Note: Why This Matters For Modern PLC Upgrades

Experience-Based Advice For System Integrators

I have seen many engineers confuse backplane models. Some assume that any two chassis can link directly. This mistake leads to costly downtime. Always consult the 90-70 series manual before designing your DCS architecture.

From my professional view, the lack of direct expansion is actually a strength. It forces clean segmentation of backplane buses. As a result, you avoid electrical noise and addressing conflicts. For new projects, consider the IC697CHS790 for larger I/O density. Use the CHS750 for remote or smaller nodes, each with its own CPU or bus expander.

Best Practices For Expanding GE Fanuc 90-70 Systems

Approved Methods To Increase I/O Capacity

Use the IC697BEM731 Bus Expansion Module. This module connects two backplanes correctly. The primary chassis holds the CPU. The secondary chassis acts as an expansion rack. You can add up to seven expansion chassis in many configurations.

Another method is to use a Genius Bus network. This network connects multiple backplanes via a bus controller. Each backplane then operates independently. However, for simple slot expansion, stick with the BEM731 module.

Moreover, verify power supply requirements. The CHS790 and CHS750 both need adequate power. The IC697PWR711 or similar supplies work best. Always ground the system properly to ensure industrial reliability.

Practical Application Scenario: Expanding A Manufacturing Line

Real-World Example Of Correct Backplane Expansion

A car assembly plant needed 32 additional I/O points. They had an existing IC697CHS790 with a CPU. They tried to add a CHS750 directly. This did not work. After contacting support, they implemented a BEM731 module. The system then recognized all slots.

This case highlights a key lesson. Always separate backplanes using bus expansion modules. As a result, the plant avoided signal reflection issues. Their factory automation uptime increased by 15%.

Frequently Asked Questions (FAQ)

1. Can I connect IC697CHS790 and CHS750 without extra hardware?

No. You need a bus expansion module like IC697BEM731. Direct connection is not supported.

2. What happens if I wire two backplanes directly?

The system will not recognize the second backplane. You may also damage the bus drivers. Avoid this practice.

3. How many expansion chassis can I add to a 90-70 system?

With the BEM731 module, you can typically add up to seven expansion chassis. Always check your CPU specifications.

4. Does the CHS750 require a different power supply than CHS790?

Both work with standard 90-70 power supplies such as IC697PWR711. However, calculate total load before installation.

5. Where can I find official GE Fanuc expansion guidelines?

Refer to the GE Fanuc 90-70 Series PLC Hardware Manual. You can also contact certified automation partners.

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