DC Power Calculator
Enter any 2 known values and press “Calculate” to solve for the others:
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DC Power Calculation
Voltage (V) calculation from current (I) and resistance (R):
V(V) = I(A) × R(Ω)
Power (P) calculation from voltage (V), current (I) and resistance (R):
P(W) = V(V) * I(A) = V 2(V) / R(Ω) = I 2(A) * R(Ω)
AC Power Calculator
Enter 2 magnitudes + 2 phase angles to get the other values and press the “Calculate” button:
AC Power Calculation
The voltage V in volts (V) is eqaul to the current I in amps (A) times the impedance Z in ohms (Ω):
Vrms(V) = Irms(A) × Z(Ω) ∠ (θI + θZ)
The angle (θV – θI) = θZ = φ is the phase angle of the load impedance and is often referred to as the power factor angle.
- θV is the voltage phase angle.
- θI is the current phase angle.
The load impedance Z may be written as:
Z = Vrms / Irms ∠ (θV – θI)
The complex power S in volt-amps (VA) is equal to the voltage V in volts (V) times the current I in amps (A):
S(VA) = P + jQ = Vrms(V) × Irms(A) ∠ (θV – θI)
The real power P in watts (W) is equal to the voltage V in volts (V) times current I in amps (A) times the power factor (cos φ):
P(W) = Vrms(V) × Irms(A) × cos (θV – θI) = Vrms(V) × Irms(A) × cos φ,
where φ = θV – θI is the phase angle between the current and voltage.
The product Vrms * Irms is referred to as the apparent power.
The reactive power Q in volt-amps reactive (VAR) is equal to the voltage V in volts (V) times the current I in amps (A) time the sine of the complex power phase angle (φ):
Q(VAR) = Vrms(V) × Irms(A) × sin (θV – θI) = Vrms(V) × Irms(A) × sin φ,
where φ = θV – θI is the phase angle between the current and voltage.
The power factor (PF) is equal to the absolute value of the cosine of the complex power phase angle (φ):
PF = |cos φ|
