Watts to VA calculation formula
S(VA) = P(W) / PF
The apparent power S in volt-amps (VA) is equal to the real power P in watts (W), divided by the power factor PF.
VA = W / PF
volt-amp = watt / PF
Power (P) = 350W
PF = 0,7
Apparent power (S) = 350W / 0,7 = 500VA