ECN Forum Forums General Topics of the Trade General Discussion Area 3 Phase Power (490 volts on a 480 volt system)

Doing the math isn't that bad.

1% is 1/100, i.e. 1% of 460V is 460/100=4.6.

So 10% is 4.6*10=46.

460V -10% is 460-46=414.
460V +10% is 460+46=506.

That's not the shortest way, but the easiest to explain and remember.

iwires figures confuse me a bit though, since 432 is 480 - 10% and 508 is close to 460V + 10%, but only close.