Convert current to apparent power
VA = Apparent power
W = Real power
W = VA × PF
For resistive loads, VA = W
VA (volt-amperes) is the unit of apparent power in AC circuits. Converting amps to VA requires knowing the voltage. This calculation is essential for sizing UPS systems, transformers, and generators.
VA = Amps × Volts. A 10A load at 120V = 1200 VA.
VA = Amps × Volts × √3. A 10A load at 480V 3-phase = 10 × 480 × 1.732 = 8314 VA.
Single-phase: VA = Amps × Volts. Three-phase: VA = Amps × Volts × 1.732. You must know the voltage to convert.
VA is the unit of apparent power - the total power flowing in an AC circuit. It includes both real power (watts) and reactive power (VAR). Transformers and UPS are rated in VA.
No. Watts = VA × Power Factor. For purely resistive loads (heaters, incandescent bulbs), PF=1 so VA=W. For motors and electronics, VA is typically 20-40% higher than watts.
UPS must handle the total current (apparent power), not just real power. Computer power supplies have poor power factor, so their VA rating is higher than watt consumption.