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Hardware Comparison: RX7I vs RX3I Series Overview

For the last two decades, the GE PAC controllers RX3i and RX7i have been in service. The RX3i controller is best for the smaller platform, and offers a high level of functionality in a compact, cost-effective package. On the other hand, RX7i is a pioneer member of the PAC control solution designed to address mid to high-level applications for OEMs, solution integrators, and end-users. With open architecture, large memory, and high performance RX7i is best for integrated solutions.

The PAC controller family depends on Proficy Machine Edition (PME) programming software for all programming, diagnostics, and configuration of hardware systems. The CPU is configured and programmed using PME tools to perform discrete and process automation for various applications.

PAC system users get the advantage of an integrated environment to configure and maintain control applications by using the PAC machine edition (PME). This one software configures a range of control equipment such as PLC, VFD, HMI, servo, and edge devices. PME is a very user-friendly graphical interface that gives drag-and-drop features for editing and rich options for developers to develop the control applications efficiently. Its support programming in Ladder Logic, C language, Functional Block diagram, and structured text.

Diagnostics are essential during troubleshooting, so PME built-in diagnostics give users the information related to controller status, timestamp data, and errors/faults. Besides, logic developments provide additional configuration for the controllers and I/O. All these features make it a flexible system to meet all user project needs.

RX3i and RX7i Technical Architecture

Both the PAC controllers use high bandwidth backplanes (2 I/O buses) that depend on VME technology for RX7i CPU and PCI for RX3i CPU. This controller architecture makes complex programming easy to create and robust to execute. One of the leading advantages of this PAC system design is the migration of obsolete platform GE 90 PLCs with interchangeable I/O modules and simple logic conversion tools.

A PAC system application supports one block-structured application architecture. This application program loads all the logic parameters to control the execution of the CPU and the I/O modules in the system. Application program developed through software and downloaded to the CPU non-volatile memory to ensure the availability. The CPU reads input bits from the module in the system. and copied it to the defined input memory locations. After the write operation, the CPU executes the entire application program in one cycle on this new data. The generated output data moved to designated output memory locations. In the last step CPU, writes the output commands to output modules in the system. That completes operation is called the sweep cycle.

RX3i and RX7i Functional Evaluation

Both the controller belongs to the GE PAC family and comes with common and some distinguishing features. RX7i is already qualified for its end of life. RX3i is continuously in production and improving its functionalities.

Central processing unit and memory

RX7i CPU belongs to a high-end Intel-based processor. The processing speed goes from 300 MHZ Celeron processor to 1800 MHZ Pentium M processor. In addition to that, the built-in memory for each processor goes from 10MB to 64 MB. In contrast to the RX3i controller, the processing speed for different CPU series goes from 300 MHZ Celeron processor to 1.2 GHz AMD G-Series Quad-Core processor. And built-in memory goes from 2MB to 64 MB.

Communication protocols

Communication is necessary to establish a controller link with external hardware and software. Both PAC controllers have multiple communication options like serial and ethernet ports. On the RX7i controller, two RJ45 Ethernet ports are available. Both ports automatically check the data rate and adjust to 10 Mbps or 100 Mbps accordingly. However, the RX3i controller has an additional port to use as a switch if required. For the MODBUS RTU and ASCII protocol, two serial ports are available. In addition to that, Ethernet port support MODBUS TCP/IP protocol, OPC UA server, Global data EGD, PROFINET, DNP3, and HART passthrough to link with other systems and devices through the ethernet port.

Chassis and remote racks

One main advantage of the RX3i over the RX7i, hot-swappable I/O module. The RX3i Universal baseplates support hot-swap capability to cut downtime. The RX3i baseplates come with multiple slot configurations starting from 7 slots up to 16. To maximize flexibility, expansion bases are available in 5 and 10 slot versions. In contrast, RX7i is a versatile controller to achieve high performance and reliable operation. The RX7i control system hardware includes the main rack and Series 90-70 expansion racks up to seven. The CPU should be in slot 1 of the chassis rack.RX7i chassis use a VME64 backplane that enhanced the bandwidth of existing VME based systems up to four times, including the current Series 90-70 systems for faster I/O throughput.RX7i support from 9 slots to 17 slot standard PAC system chassis with rear or panel mount options.RX3i supports a 32 points discrete I/O module while RX7i supports up to 64 points discrete input out module. Regarding analog input and output, RX7i supports additional analog inputs up to 64 and analog outputs the same as RX3i up to 16.

Power Units

RX7i power source modules easily install into the main PLC rack with I/O, and its work with all CPUs. Power input mode support both AC/DC current. With low capacity power supply, it can support up to 100W total output, and no forced air colling requires. Furthermore, the high-capacity power supply provides the power up to 350W but requires a forced-air cooling system mounted at the bottom of the rack. RX7i-System power supplies have built-in protection for power factor corrections through auto-ranging, over-temperature, over-current, and over-voltage fault conditions.

In contrast, the RX3i power supply modules easily plug into the main rack just like I/O, and they support any model controller CPU. Each module is auto-ranging, so with different incoming power levels, there is no need to set jumpers, and modules have built-in current control to save the power supply from a direct short and avoid hardware damage. Due to advanced diagnostics and switching options, this power unit can be integrated to achieve redundancy and incremental capacity.

System health check

In addition to the system diagnostics for PAC controllers, the embedded RX7i CPU ethernet port gives a web server option. Each Ethernet port supports a web server to store and maintain web pages accessible through FTP and HTTP protocol. Built-in API allows the user to design the custom web pages to display required PLC data in different formats. A standard set of pre-define web pages include a home page, controller error table, I/O error table, and reference data table. Web server capability is not available for rack-based ethernet interface modules.

High Time Availability

To increase process stability and avoid downtime, both RX7i and RX3i comes with redundancy feature. In RX7i CRE series come with built-in redundancy, and the CPE series without it. It comes with a hot standby CPU redundancy feature, which allows processor critical application to keep working in case of single component failure. A CPU redundancy system includes two controllers, the active one and the standby, to take action in case of failure. Both controllers keep themselves in sync after every cycle of execution. For RX7i, if the same CPU model is not available, you can replace it with the other module but with the same class.

RX3i also supports hot standby (HSB) CPU redundancy like RX7i but has the advantage of hot-swapping modules to the same extent allowed in non-redundant systems. Modules that support hot-swapping can be removed and replaced in the RX3i main rack and remote rack while the system is powered up.

RX3i High end solutions with advanced connectivity

The PAC RX3i controller is part of GE’s industrial control solution (IICS) line that enables the user to get an insight into an application with advanced connectivity features of the industrial internet of things (IIOT). Controller CPE305/CPE310 through embedded ethernet port gives open productivity and connectivity unified architecture (OPC UA) for connection with remote systems. It enables the user virtual access from anywhere to control manufacturing processes. That means management can do predictive maintenance and planned downtime based on data gathered from your pieces of equipment. By using advanced solutions and plant analytics can reduce unexpected downtime and unplanned maintenance jobs. With the latest in security tools, plant data and network is secure from software threats and hacking attempts.

Additional features for the RX3i and RX7i

Additional features in RX3i and RX7i through additional modules;

  1. Built-in USB port interface available in all RX3i CPE series.
  2. RX3i CPE330/440 support Media Redundancy (MRP) and PROFINET System Redundancy (PNSR)
  3. RX3i 400 series worked in -40°C to 70°C temperature.
  4. RX7i supports many communications options for distributed control or I/O, supporting a lot of communication protocols and configurations. Some I/O communications modules allow for many remote drops or more racks, while others provide an interface for GE products up to 7500 feet away from the controller.

Both RX3i and RX7i belong to the GE PAC product series, both controllers are designed for high-speed I/O and fully capable to control the complex process and large-scale Inputs/Outputs. RX3i has an edge over RX7i in its advanced communication options and certification to use in marine environments.

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This entry was posted on October 12th, 2020 and is filed under GE Fanuc, General, Hardware Comparison, PAC, Technology. Both comments and pings are currently closed.

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