how to calculate amperage from watts
The phase current I in amps (A) is equal to the power P in watts (W), divided by the power factor PF times the RMS voltage V in volts (V): I (A) = P (W) / (PF Ã V (V)). The power factor of resistive impedance load is equal to 1.alculation with line to neutral voltage. The phase current I in amps (A) is equal to the power P in watts (W), divided by 3 times the power factor PF times the line to neutral RMS voltage V L-N in volts (V): I (A) = P (W) / (3 Ã PF Ã V L-N(V)). The power factor of resistive impedance load is equal to 1.