In an AC (alternating current) circuit, reactive power is the power that flows back and forth between the source and reactive elements (inductors and capacitors) without doing any actual work. It is necessary to maintain the voltage and current phase relationship in the circuit.
Reactive power is measured in volt-amperes reactive (VAR) and is represented by the symbol "Q."
To calculate the reactive power in an AC circuit, you need to know the voltage, current, and the phase angle difference between them. Here's the formula for calculating reactive power:
Reactive Power (Q) = V à I à sin(θ)
Where:
V is the RMS voltage (root mean square voltage) in volts.
I is the RMS current (root mean square current) in amperes.
θ is the phase angle difference between the voltage and current in radians.
Keep in mind that for accurate calculations, both the voltage and current values should be in RMS values, which represent the effective or average power in an AC circuit.
The phase angle (θ) between voltage and current can be positive or negative depending on the circuit elements. For inductive elements (e.g., inductors), the current lags behind the voltage, so the phase angle is positive. For capacitive elements (e.g., capacitors), the current leads the voltage, so the phase angle is negative.
Once you have the values for voltage, current, and the phase angle, plug them into the formula to calculate the reactive power (Q) in the circuit.