Continous diagnostics in the control circuit
The control circuit is an important part contributing to the proper functioning of a system so that it can operate as planned. If the 24 V supply in the control panel should drop for whatever reason, this will result in the halting of the application and thus in costs due to the production stoppage. To avoid this, an eye should be kept on the 24 V supply using end-to-end and simple diagnostics. This applies to both the power supply and the protection of the individual 24 V load feeders. With the help of diagnostics and monitoring, an overload, short circuit in the control circuit, and failure of the DC power supply can be correctly reported and responded to. This tip shows you how this can be implemented quickly and easily.
Tips for you!
A power supply is at the heart of automation, which is why it is all the more important to know the status of the DC power supply in the control panel, in particular this means the capacity of the device – are there still reserves or is the device already being operated close to or even in overload. With the standard power supply SITOP PSU6200, all important data is transmitted to the controller: More information about this:
To easily and clearly read in, evaluate, and display on an operator device the signals of the SITOP PSU6200 diagnostics interface, function blocks and faceplates are available for SIMATIC S7.
Selectivity modules distribute the load current across several 24 V DC load feeders and monitor them reliably for overload and short-circuit conditions. The electronics permit brief current peaks caused, for example, by high inrush currents, but load feeders are disconnected in the event of an extended overload. This is ensured even on high-resistance lines. Even if the power supply unit could deliver the required tripping current, in such cases, miniature circuit breakers fail to trip or trip too late. The selectivity modules continue to reliably supply the intact feeders with 24 V DC, which can prevent a total system failure – further information can be found here:
Selective monitoring of 24 V load feeders
If a system is intended for use in the North American market in accordance with UL standards, other norms and standards must be used as the basis when used in accordance with IEC. For the control circuit, this primarily concerns the correct dimensioning and protection. What has to be paid attention to can be found in the following white paper.
Especially for SIMATIC IPCs, a dropping power supply can lead to problems, since in addition to data loss, the failure can damage the hard drive or SSD requiring replacement. The IPC should thus always be protected by a matching DC UPS. In the event of a fault, the IPC will be shut down safely and properly – with data remaining secure. Which UPS fits which IPC can be found here:
With the help of the free engineering & monitoring software “SITOP Manager,” the communication-capable DC UPS solutions from SITOP are put into operation. The SITOP Manager monitors and shuts down multiple PCs in a targeted manner via the SITOP Shutdown Service in the event of a power failure; it also provides important information during operation, e.g., about the status of the buffer components.
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