![]() ![]() You will find more information about AC power in our AC Power Calculator, VA to W Calculator, and Three-Phase AC Power Calculator.ĭit artikel is geschreven door Anatoly Zolotkovĭit deel van de Omrekentool bevat een aantal rekenmachines die kunnen worden gebruikt bij de verschillende aspecten van elektrotechniek, elektronica en RFT. Where I rms and U rms are the RMS current and RMS voltage, and φ u is the phase shift between the voltage and current. ![]() This, in turn, allows generating less power and use conductors with a smaller cross-section in power lines. This reduces the amount of energy that is required to be produced at the power plant and transmit by the power lines. Because of this fact, shunt capacitors connected in parallel to inductive loads can supply reactive power needed by inductances, and thus it is not necessary to transmit this reactive power over power lines. Note that this is merely a convention because the majority of electricity consumers (for example, electric motors) are resistive-inductive loads. Inductors absorb reactive power whereas capacitors supply reactive power. Reactive power is associated with reactive components of the circuit. Both units are not part of the SI system. The apparent power is measured in volt-amperes (VA) and the reactive power is measured in volt-amperes reactive. The instantaneous and active power is measured in watts, which is the SI unit for power. The power triangle P is the active power, Q is the reactive power, | S| is the apparent power, which is the absolute value of the complex power S, and φ is the phase difference angle between the voltage and the current. For an inductive load with the lagging current, the complex power vector will be in the I quadrant. For a capacitive load, the current is leading the voltage and the complex power vector will be in the IV quadrant of a rectangular coordinate system. The angle φ in the power triangle is the phase difference in degrees or radians between the current and the voltage. The relationship between active power in watts, reactive power in vars, and apparent power in volt-amperes in an AC circuit can be represented by the three sides of a right-angled triangle, which is called the power triangle. Reactive power Q measured in reactive volt-amperes (var).Apparent power |S| measured in volt-amperes (VA).Complex power S measured in volt-amperes (VA).Instantaneous power p measured in watts (W).The following terms are used to describe the power, which is the rate of energy flow in AC circuits: ![]() Active, Reactive, Apparent and Complex Power The equipment used for energy generating and transmission (generators, conductors, transformers, and switches) must have a greater size and be more powerful to carry not only the current that is used to give the active energy, but all current that is necessary to provide the active and reactive power.Īnimation of instantaneous AC voltage u(t), current i(t) and power p(t) with the load changing from inductive (the current lags the voltage) through active ( φ = 0, the current and voltage are in phase, the power is positive) to capacitive load (the current leads the voltage).Īll practical loads have resistance, capacitance, and inductance therefore, they consume both active and reactive power. In this situation, no energy is consumed, but at the same time, the current heats the wires. The voltage and current in a purely reactive (inductive or capacitive) load are 90° (π/2 rad) out of phase and the energy goes back and forth between the source and the load. In a purely resistive load, the current and voltage reach their peaks and reverse their polarity at the same time, therefore, at every moment their product is positive or zero and the energy flows only in one direction or does not flow at all if both the voltage and the current is zero. Where i p is the peak current, u p is the peak voltage, ω is the angular frequency, t is the time and φ u is the phase shift between the voltage and current. For a sinusoidal alternating current, the instantaneous power is the product of instantaneous current and instantaneous voltage (see the animation below): Active, Reactive, Apparent and Complex PowerĬonsider a simple AC circuit consists of a power source generating a sinusoidal voltage and a linear load. ![]()
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