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Power supplies often accept an input range of 90-264Vac. I am wondering where the 264 comes from.

A couple of random examples from power supplies available:

  • 85 - 264 Vac input range (100 - 240 Vac nominal)
  • Takes universal inputs (90-264 Vac, 47/63 Hz)
  • External Power Supply 90 to 264 VAC
  • Input voltage 90-264Vac

I understand that large parts of the world are 220-230V. I also understand that 277V may be available, as well as 208V.

But where exactly is the 264Vac limit from?

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Just for a bit of background on why 240V is often used you can see here: en.wikipedia.org/wiki/Mains_electricity#Voltage_levels – PeterJ Jul 4 '14 at 4:09

264/240 = 1.1

In other words, the power supply is allowed to fluctuate by ~10% over nominal and the supply will still work as designed.

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10% tolerance on AC mains is a very reasonable value. In fact EU allows a +/- 10% tolerance on the 230VAC mains grid. That leaves the question: which country uses 240VAC and does it indeed allow a +10% tolerance? – jippie Jul 4 '14 at 6:10
The UK used to use 240VAC – Andy aka Jul 4 '14 at 7:50
If I'm not mistaken, it is possible to get 240V in the US because most 120V outlets are created by spliting this in the breaker box. – helloworld922 Jul 4 '14 at 13:47

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