All-in-one PID-SSR, a super building block

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October 2004 PLCs, DCSs & Controllers

The layout and design of current temperature control systems can be very complex. Running too many PID control loops makes the PLC system sluggish which causes a fluctuation in temperature. As the design engineers are trying to solve this problem they are finding that their control loops are becoming increasingly expensive due to high installation and maintenance costs. The challenge for machine automation is to use modern technology to provide a simple solution.

The Geflex is an advanced intelligent power SSR (or power PID controller), which is a fully programmable PID solid state relay. Described as an 'integrated control and power system for multizone temperature control' the Geflex product is a perfect marriage of a SSR and a PID controller, all in one DIN mount module with various bus connection possibilities.

The Geflex concept cuts down on 30% of cabling and installation time, it can be located close to the switched load and to the temperature sensor and communicates with a range of MMI interfaces via modern bus connections. Geflex simplifies machine design and is available in Profibus, Modbus and CAN-OPEN bus.

In practice the benefits are:

* Lower design and manufacturing costs.

* Less cabling for the maintenance technician to wade through on site.

* Troubleshooting a machine in a production environment is quick, resulting in less downtime and maximising production time.

The biggest benefit is the effect on the machine PLC: it has always been a problem running many PID control loops in the PLC, as they slow down the system. Adding Geflex to the PLC offloads this overhead onto the control point where it should be, resulting in a far superior control on each loop while reducing the size of the required PLC. This results in major cost savings. OEMs have hailed this new concept a blessing long awaited.

Programming is easy

Set-up, programming and operator interface is via a PC or the new Chatty range of man-machine interfaces or the DigiStar industrial PCs from Gefran. The Winstrum software is similar to the popular version used for the panel mounted controllers and digital indicators from Gefran and allow quick and easy timing.

Geflex GFX master modules carry a fieldbus interface, slave modules are without and are available in ratings between 25 A and 120 A switching capacity. Geflex can handle single and three-phase loads up to 480 V a.c. and offers all modern PID functions (14 control algorithms), up to three relay outputs for cooling and six configurable alarms, digital input for dual setpoint selection and auto-manual switching or resetting of latched alarm functions.

The new Geflex PID-SSR has more functions for automation than conventional PID controllers and the on-board current transformer monitors the load and reports on load failure immediately. In addition an optional voltage transformer allows monitoring of the mains voltage, power and energy levels.

For more information contact Neil Coetzer, UniTemp, 011 392 5989.

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PLCs, DCSs & Controllers

All-in-one PID-SSR, a super building block

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