Single-Phase AC Power

$$ P = V \times I \times PF $$

$$ I = \frac{P}{V \times PF} $$

Where: P = Power (Watts), V = Voltage (Volts), I = Current (Amperes), PF = Power Factor (typically 0.8 for AC)

Three-Phase AC Power

$$ P = \sqrt{3} \times V_{LL} \times I \times PF $$

$$ I = \frac{P}{\sqrt{3} \times V_{LL} \times PF} $$

Where: $V_{LL}$ = Line-to-Line Voltage (Volts)

Battery Sizing (AH)

$$ AH = \frac{Total\,Wattage \times Backup\,Time}{Battery\,Voltage} $$

Where: AH = Ampere-Hours, Backup Time is in Hours

AC to DC Conversions

$$ P_{DC} = P_{AC} \times \eta $$

$$ I_{DC} = \frac{P_{AC} \times \eta}{V_{DC}} $$

Where: $P_{DC}$ = DC Power (Watts), $P_{AC}$ = AC Power (Watts), $\eta$ = Efficiency, $I_{DC}$ = DC Current (Amperes), $V_{DC}$ = DC Voltage (Volts)

Ohm's Law & Power Conversions

$$ P = V \times I $$

$$ V = \frac{P}{I} $$

$$ I = \frac{P}{V} $$

Where: P = Power (Watts), V = Voltage (Volts), I = Current (Amperes)