Using redundant DIN rail power supplies for system reliability
With a redundant system design, in the unlikely event that a power supply fails, the remaining unit will continue to power the load. The faulty power supply can then be replaced during scheduled maintenance without having to shut down a production line.
TDK Lambda has highlighted how the its DRM40 series of 20-40A DIN rail redundancy module can be used in three configurations:
1) As a redundant system requiring a maximum load current of 20A. In this configuration, two 20A power supplies are connected to the DRM40 and in the event that either power supply loses its output the other unit will continue to supply the 20A load. Internally, the OR’ing FETs will block reverse currents, if one of the power supplies fails short circuit; this allows the load to continue receiving power
2) Alternatively, two power supplies can be connected in parallel and, using the current balance function, the outputs can be adjusted to provide equal current to supply a load up to 40A. Balancing the currents avoids one power supply from providing the majority of the load, running hotter and reducing its field life.
3) The third option is to use two DRM40 modules to support a 40A redundant load. Here, two 40A power supplies are each connected to a separate DRM40, with the two 20A inputs connected in parallel. If either power supply loses its output, the other units will continue to supply the 40A load. Again, internally, the OR’ing FETs will block reverse currents if one of the power supplies fails short circuit, allowing the load to continue receiving power.
The DRM40 series can be used in N+1 redundancy applications or to parallel two power supplies for additional power. A current balancing LED indicator which is illuminated when both power supplies have been adjusted to deliver the same current, and two isolated alarm signals indicate the output voltage status of each power supply. Internally the DRM40 has a low 200mV voltage drop.
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