Why does the voltage across the DC-link capacitor in a boost PFC circuit usually equals 400 Volt?

In a boost PFC circuit connected to the grid (230Vrms,Europe) the DC-link voltage is usually regulated to 400 Volt. Why is that? Is that because it is efficient to boost it to that particular voltage? If so, why then?

Answer

As it works as a boost converter, output should be higher than input. For Europe grid voltages, maximum value is 265Vrms. So the output should be higher than 265 × 1.414 = 375Vdc. 400V is well above this and a good rounded number.

One more thing: Generally an isolated DC/DC converter follows PFC pre reg, so a higher voltage will increase the stress on the switching transistors (both PFC pre reg's and DC/DC converter's), and also increase the number of turns of the power transformer.