A DC UPS and You.

Adding a DC UPS to a PLC system is a wise investment in redundancy allowing 24vdc control systems to continue to function for hours without power. This becomes doubly important when a PLC with alarms and network connectivity is in use. Having the PLC stay online to allow a technician to connect to the unit remotely to diagnose a power failure or head off a much larger problem before it occurs.

With the range of power supplies and UPS modules available a designer can incorporate redundant power supplies and UPS modules easily into a panel.Redundancy modules can couple and decouple units wired in parallel as required to maintain output voltages. A UPS in parallel can “top-up” a power supply with an under-voltage output averting damage to sensitive electronic equipment.

DC-UPS units take up less space and generate much less heat than an AC UPS making them ideal for control panel environments. Their small form factor and DIN rail mounting allow a UPS to be included along side a power supply in any medium to large control panel.

Modern DC-UPS’s have smart features making them exceedingly reliable:

  • State of Charge (SOC): indicates the remaining back-up time and level of charge on the battery.  This gives you the ability to see the amount of available time left at a quick glance.
  • State of Health (SOH): indicates the remaining service life of the battery module.  The history of the battery module is recorded and then provides an indication of when the battery needs to be replaced, before it becomes a concern.
  • State of Function (SOF): indicates the capacity of the battery module.  The available capacity of the battery is provided, indicating how well the battery is accepting the charge and if the full capacity is still available.


Using 24VDC control is convenient for use with common solenoids, keeping a panel low voltage, and the redundant options available using a DC-UPS. Its an option worth considering in your next control panel design.


Leave a comment

Comments will be approved before showing up.