Volts is not a unit of power, it is a unit of voltage (potential difference).
Three phase kvA is Root 3 times to its single phase kvA.
Its voltage and current rating depend on the type of winding arrangement.
There are generally two type of winding star(Y, also known as wye) and delta(Δ).
Line voltage in star connection is 1.73 times to its phase voltage whereas line current is same to phase current.
Just reverse the data for delta connection. Line voltage is same as phase voltage but line current is times of phase current.
Single phase voltage is 230 and 3 phase is 240(phase).