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Modular overload relay eases installation and maintenance

06 May, 2014

Rockwell Automation has developed a modular electronic overload relay incorporating a patented current-measurement technology that makes it one of the smallest on the market, while offering a wide 10:1 FLA (full-load amperage) range – thus simplifying selection and reducing inventories.

The modular design of the Allen-Bradley E300 relay allows users to tailor the device to their exact needs by linking sensing, control and communication modules:

•  the sensing modules are available with a combination of current, voltage and earth-fault-sensing capabilities, in contactor-mounting, panel-mounting and pass-through styles;

•  the control modules are available with various AC and DC digital inputs, as well as positive temperature coefficient (PTC) and earth-fault options; while

•  the communication modules allow the relays to be used on EtherNet/IP and DeviceNet networks, and in stand-alone applications.

“As adoption of electronic-overload-relay technology has risen over the past decade, so have practical expectations,” says Rockwell's global product manager, Bill Martin. “Customers told us they value the technology’s remote monitoring and predictive trip alerts, but they also want designs that simplify programming, preserve network nodes, save wiring time, ease maintenance and minimise catalogue numbers.”

Rockwell's E300 electronic overload relay is one of the smallest available

The relay contains an embedded DeviceLogix logic engine with pre-programmed motor-control logic for local and remote motor operation. A single cable connects it to a control station for local motor operation, eliminating the time and costs of traditional hard-wiring, and reducing the need for discrete input points on the device. To make it easier to swap the E300 overload relays, a copycat function allows users to download pre-stored relay configurations at the push of a button.

There is a choice of digital and analogue expansion I/O modules to reduce wiring times and network node counts. The digital I/O modules provide four inputs and two relay outputs, making them ideal for complex starter installations where users need more I/O than provided in the base relay. The analogue expansion I/O modules allow users to choose between traditional analogue signals and resistance temperature detectors (RTDs) embedded in the motor. Rockwell claims that the relay is the first to combine the ability to receive traditional analogue signals and RTD sensor signals in one device.

A dual-port EtherNet/IP option simplifies network wiring, allowing the relays to be daisy-chained and eliminating the need for an Ethernet switch. An embedded Web server allows maintenance personnel to integrate the relay via a Web browser running on an Internet-enabled device, without needing special software. To maintain uptime in the event of a network node interruption, the relay supports a device-level ring (DLR) network topology.

The relay integrates with Rockwell Software’s Studio 5000 control environment via an add-on profile. Users are just five mouse clicks away from communicating data between the device and a Logix controller.

The relays are formed by combining sensing, control and communications modules

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