Power protection devices like UPS systems are typically referred to in terms of VA, kVA or even MVA. This measurement refers to the Apparent Power drawn by a load and is calculated as follows:
Apparent Power (VA) = Supply Voltage (V) x Amps (A)
In the formula (V) is the Root Mean Square (RMS) of the supply voltage and the Amps is the current drawn by the load. Ideally it is important to measure the current drawn at start-up and after the start-up process has settled down to the a running load current. To measure the Apparent Power drawn by a three phase load the formula is applied per phase and then the individual VA results are added together to give a final total.