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Control voltage load monitoring and distribution made easy

17 July 2017

Conventional solutions for 24 V DC circuits are time consuming and take up a lot of space in the control panel, but now there’s a better way: maxGuard from Weidmüller.

Providing control voltage supplies to field-mounted devices is a headache for every panel builder, especially when the overcurrent and short-circuit protection are also needed. 

Even in these days of fieldbus systems, most control panels still need to deliver control voltage supplies to numerous field-mounted devices. The usual solution is simply to provide a terminal rail within the control panel and, if this is well designed and implemented, using versatile modern terminals like those in Weidmüller’s Klippon Connect application range, this is a perfectly satisfactory approach.

Things get more complicated, however, when overcurrent and short-circuit protection are needed, either on a circuit-by-circuit basis or for groups of circuits. In principle there’s no problem in providing such protection – any number of protection devices are available on the market, and some can even be mounted on terminal rails alongside the terminals. Using these modules, however, creates a range of practical problems: they take up a lot of space – and space in control panels is always at a premium –their use often involves time-consuming additional wiring – and using conventional circuit breakers in 24V dc systems requires more complex product selection, as well as a more expensive high spec power supplies to offer reliable tripping.

To provide a more practical and more convenient solution, Weidmüller has developed the innovative maxGUARD system, which is now available as part of the Klippon Connect product portfolio. Like all good ideas, the idea behind maxGUARD is very simple – it combines load monitoring and power distribution in the same device.

At the heart of the maxGUARD system, which has been developed specifically for use with 24 V DC control supplies, are modules that feature integrated load monitoring and protection. Weidmüller has combined the functions of power distribution and circuit protection in remarkably compact devices – for loads of up to 6 A, for example, maxGUARD modules are just 6.1mm wide.

In typical control panels, Weidmüller has found that 50 percent less space is needed to provide protected control voltage supplies for field devices using maxGUARD than would be needed with the usual combination of terminals and separate protection devices. Another major benefit is that wiring between the terminals and the protection devices is no longer needed, which significantly reduces panel wiring time and costs.

To ensure that they offer economical solutions for every application, maxGUARD modules are available in a wide range of types. The range includes single-channel modules with tamperproof fixed overcurrent ratings from 1 A to 10 A, and types with user-adjustable overcurrent settings up to 12 A. Four-channel modules, with ratings up to 6 A per channel, are also available. 

To facilitate commissioning and fault finding, the modules have integrated test points and further modules are offered with disconnect levers to provide convenient galvanic isolation.

Including both single- and four-channel modules in the maxGUARD range means that solutions can be cost-effectively matched to the application. If five channels are needed, for example, it is not necessary to buy two four-channel modules, as is the case with many other protection solutions, all that’s needed is one four-channel module and one single-channel module.

maxGUARD load monitoring modules provide instant visual confirmation of status using a green/red LED indicator. If the LED is steady green, load monitoring is enabled and operating normally. Flashing green indicates that the load current is 90 percent or more of the trip value. 

If the LED shows steady red, load monitoring has been disabled and, if it shows flashing red, the overcurrent or short-circuit protection has operated and the protected circuit has been disconnected. The maxGUARD range includes an optional alarm module that allows status information to be sent direct to a PLC or other control device.

For applications where several circuits in the field need to be connected to the same protected supply channel, and to reduce wiring time to an absolute minimum, the maxGUARD system includes a comprehensive range of cross-connectors, complemented by terminal-only modules without integral protection. Also available in the range are power-feed modules to accommodate the connections between the control voltage power supply and the maxGUARD system.

The maxGUARD system uses PUSH IN technology for connections, ensuring fast reliable wiring. The system has a maximum overall current rating of 40 A and can operate from -25 to +55ºC without derating. Power feed modules can accommodate cables up to 16mm2, and the electronic load monitoring modules can accommodate cables up to 2.5mm2.

With maxGUARD from Weidmüller, panel builders can now easily implement fail-safe maintenance-friendly control voltage distribution systems that incorporate comprehensive overcurrent and short-circuit protection. Important additional benefits include large savings in the panel space needed, compared with conventional solutions, and a significant reduction in wiring time. And, of course, maxGUARD users benefit from Weidmüller’s renowned product quality and outstanding technical support.


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