A “Beginner’s Guide” to Fault Tolerant Power Supplies

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The effectiveness of getting a fault tolerant power strategy was demonstrated after hurricane Katrina hit the Gulf Coast in 2005. A monetary news tv station interviewed the heads of two telecom carriers to discover out when their phone companies could be operational once more. The interview was very quick – “we by no means misplaced service” they replied.

The phone methods we take with no consideration have costly and sophisticated again up methods. Fault tolerant power provides are supported by battery banks, mills and uninterruptible power provides. Giant Industrial complexes have additionally carried out comparable methods - having an oil refinery cease manufacturing may end up in monumental sums of cash being misplaced!

For these with much less in depth budgets, this temporary article will clarify the advantages, terminology and ideas on how to implement a comparatively low price, however efficient system.

Why have redundant power provides?
Think about a 24VDC 10A power provide driving motors and sensors on a conveyor based mostly manufacturing line. For 2 or three years every thing works nice, then one Friday (all the time on the finish of the month), the power provide fails inflicting the conveyor to cease. Even when a spare half is in inventory, it might nonetheless end in 30 minutes of pricy misplaced manufacturing.

If two equivalent power provides had been put in in a fault tolerant, redundant mode, the remaining (good) unit would have continued to power the manufacturing line. The failed power provide might then get replaced at a extra handy time throughout routine upkeep.

Continuously Used Terminology

An expression the place N is the variety of power provides wanted to run the system. The straightforward two power provide system talked about above could be thought of 1+1. A triple redundant system (the place two failures would have to happen to shut the system down) could be designated 1+2.

Some tools is operated 24 hours a day, 7 days per week, permitting no time to convey the system down for upkeep. On this case the failed power provide have to be “swapped” out and a new one inserted with out disruption to tools operation.

ORing diodes
Within the uncommon occasion of a power provide failing with a shorted output, low voltage-drop ORing diodes block that quick from bringing down the system power.

Present share
Some power methods make use of a way of balancing the present between the power provides to enhance discipline life. This may be an digital sign wire that hyperlinks the power provides collectively or a change* on the power provide that initiates a slight drop within the output voltage as extra present is drawn. (*Widespread on high power DIN rail models)

Two Methods of Implementing Fault Tolerance

DIN Rail mount
For the instance listed above, the only off-the-shelf resolution is to use a diode “ORing” module and two power provides. Right here we're utilizing Lambda’s DIN rail mount DLP-PU module and two 24V 10A DLP240-24-1/E power provides.

Tip: When wiring the system, make sure that the cable lengths from the output of the power provides to the ORing module are equal. This can assist optimize the efficiency and lifetime of the power provides.
Contained in the diode ORing module are two diodes and two alarm relays. Even within the occasion of 1 power provide failing with an internal quick circuit, the remaining unit will proceed to ship power. See under.

Tip: - It is necessary to determine power provide failure utilizing the relay alarms to flag the necessity for upkeep. Engineers generally overlook this which may end up in a second failure unexpectedly bringing the system down!

Rack MountSystem Engineers requiring extra power are turning to the communications type racks. These subtle low price methods permit power provides to be hot-swapped and are available utterly self contained. An instance of such a product is Lambda’s FPS sequence.
Benefits of this resolution embrace:

  • Straightforward mounting into an ordinary 19” rack
  • Multi function resolution
  • Hotswap succesful (ORing diodes or MOSFET switches built-in)
  • No instruments are required for alternative of a provide
  • Excessive density, low profile (1.75”)
  • Off the shelf components
  • Absolutely security accredited
  • All vital warning alerts included
  • 12V, 24V, 32-36V and 48V outputs

Click on on http://www.lambdapower.com/products/fps-series.htm for an animated instance.

Lastly, one vital note
A firm needed to make sure that within the occasion of a power provide failure their system would proceed to function. A battery was put in throughout the power provide output to give 24 hours uptime within the occasion of a power provide failure.

Sadly no thought was given to how anybody would know that the system wanted upkeep! The power provide did finally fail and the battery saved the system up for 24 hours earlier than it discharged leading to a system shutdown. A easy alarm circuit might have prevented that.

In case you take Lambda’s suggestion to make investments slightly extra cash up front to make your power system safer, take a look at your system to be sure to have it proper!