Name: ac power in series and parallel circuits
Uploaded: 2024-07-08T13:19:51.000Z
Duration: 1 min 15 s
Channel: JoVE

Le principe de conservation de l’énergie CA stipule que les puissances complexes, réelles et réactives générées par la source sont équivalentes aux puissances complexes, réelles et réactives totales consommées par les charges.
Ce principe peut être illustré par un modèle de circuit simplifié.
L'impédance totale du circuit est calculée en premier, puis déterminée le courant total de la source.
La puissance complexe de la source est ensuite calculée à l’aide du conjugué complexe de ce courant et de la tension de la source.
En séparant les parties réelles et imaginaires, il est possible d’obtenir la puissance active et réactive de la source.
Ensuite, la chute de tension aux bornes de chaque charge est calculée.
La puissance complexe est déterminée en prenant le produit du courant conjugué et de la chute de tension aux bornes de chaque section. De là, les puissances réelles et réactives sont déduites.
En comparant toutes les puissances calculées, il devient évident que la puissance de la source est égale à la somme de la puissance des sections individuelles, confirmant ainsi le principe de conservation de l’énergie.
Ce principe s’applique indépendamment des charges connectées en série ou en parallèle.

conservation de l'alimentation secteur

Conservation of AC Power

Le principe de préservation de l’énergie s’applique aux circuits alternatifs et continus. Ce principe, appliqué au courant alternatif, affirme que les puissances complexes, réelles et réactives produites par la source sont égales aux puissances complexes, réelles et réactives totales absorbées par les charges. Lorsque deux impédances de charge sont connectées en parallèle à une source alternative V, la puissance complexe fournie par la source peut être calculée à l'aide de la relation

<img alt="Equation 1" src="/files/ftp_upload/15121/15121_Equation_1.svg" style="height: 18px;">

où S1 et S2représentent respectivement les puissances complexes délivrées aux charges Z1 et Z2. Si ces charges sont connectées en série avec la source de tension, la puissance complexe fournie par la source reste inchangée. Cela suggère que peu importe si les charges sont connectées en série ou en parallèle (ou dans toute autre configuration), la puissance totale fournie par la source est égale à la puissance totale reçue par la charge. En général, pour une source connectée à N charges, la puissance complexe est donnée par

<img alt="Equation 2" src="/files/ftp_upload/15121/15121_Equation_2.svg" style="height: 15px;">

Cela implique que la puissance complexe totale d’un réseau est la somme des puissances complexes de ses composants individuels. Cela est vrai pour la puissance réelle et la puissance réactive, mais pas pour la puissance apparente. Cela exprime le principe de conservation de l’énergie CA. De là, on peut en déduire que le flux de puissance réelle (ou réactive) provenant des sources d’un réseau est égal au flux de puissance réelle (ou réactive) vers les autres composants du réseau.

Conservation de l'alimentation secteur

Le principe de conservation de l’énergie AC stipule que les puissances complexes, réelles et réactives générées par la source sont équivalentes au complexe total, ...

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ac power in series and parallel circuits

AC power in series and parallel circuits follows a power preservation rule. In AC circuits, the complex power, real power, and reactive power produced by the source are equal to the total complex, real, and reactive powers absorbed by the loads.

When two load impedances are connected in parallel to an AC source V, the source power can be written as the sum of the complex powers delivered to loads Z1 and Z2. If those same loads are connected in series with the voltage source, the complex power supplied by the source stays the same. This shows that the total power from the source does not depend on the load arrangement.

The same idea extends to a network with N loads. The total complex power is the sum of the complex powers of the individual components. The rule also applies to real power and reactive power, but not to apparent power. This is the principle of AC power conservation, and it means the real or reactive power leaving sources in a network equals the real or reactive power absorbed by the other components.

AC Power in Series and Parallel Circuits

instantaneous power

AC Power and Phase Shift

Instantaneous power in an electrical circuit comes from the voltage across an element and the current through it. It is written as p(t) and follows the passive sign convention. For sinusoidal input, this product helps show how power changes at each moment. When instantaneous power is expanded, it has two parts. One part is constant and depends on the phase difference between voltage and current. The other part is a sinusoidal term that varies at twice the frequency of the voltage or current. <br...

average power

Power Consumption in AC Circuits

Power consumption in AC circuits is often described with average power. In practical electrical work, the changing value of instantaneous power is less useful than the average over a time period. Average power is found by integrating instantaneous power over that time and then dividing by the duration. The time-domain expression for average power comes from simplifying the equation for instantaneous power. In that form, one cosine term averages to zero over a complete cycle. The result does...

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RMS Value for AC Power Measurement

The RMS value, or effective value, helps measure how much power a periodic voltage or current can deliver. It is the direct current, or DC, value that gives the same average power to a resistor as the periodic signal does. This idea is especially important in AC circuits. To find the effective value of current, calculate the root mean square, or RMS, current. First square the instantaneous current values over one period. Then find the mean of those squared values and take the square root. The...

complex power

Power Triangle in AC Circuits

Power triangle and complex power help describe how an AC load uses energy. Engineers use complex power to capture the combined effect of parallel loads. It gives a full picture of the power consumed by a specific load. Complex power is found by multiplying voltage by the complex conjugate of current. Using rms values, it is written with the rms voltage phasor and the complex conjugate of the rms current phasor. It can also be written in terms of load impedance. The magnitude of complex power...

conservation of ac power

AC power in series and parallel circuits follows a power preservation rule. In AC circuits, the complex power, real power, and reactive power produced by the source are equal to the total complex, real, and reactive powers absorbed by the loads. When two load impedances are connected in parallel to an AC source V, the source power can be written as the sum of the complex powers delivered to loads Z1 and Z2. If those same loads are connected in series with the voltage source, the complex power...

power factor

Power Factor and AC Load Behavior

Power factor describes how voltage and current behave in an AC load. It is the ratio of average, or active, power to apparent power. The power factor angle is the phase difference between voltage and current, and the cosine of that angle gives the power factor. It also matches the angle of the load impedance. Power factor shows how much apparent power becomes real, or average, power. Its value ranges from zero to one. When a load is purely resistive, voltage and current are in phase. In that...

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Reducing Reactive Power in AC Loads

Power factor correction helps AC systems use electrical power more efficiently. In a factory circuit, transmitted power includes apparent power, which is made of active power and reactive power. Power factor is the ratio of real power, measured in kW, to apparent power, measured in kVA. It shows how much of the supplied power becomes useful work. A low power factor often happens when an inductive load draws too much reactive power. This creates a lagging power factor. It can also cause large...

the power superposition principle

Power from Multiple AC Sources

Power from multiple AC sources is found by adding the effects of each source separately. In a circuit with two sinusoidal voltage sources, each source acts independently. The superposition principle says the total current is the sum of the currents produced by each source alone. If those currents are labeled i1 and i2, they combine to give the total current. Instantaneous power is the power at one moment in time. In this circuit, it equals the square of the instantaneous current times the...

the maximum power transfer theorem

Matching Load Impedance for Maximum Power

Maximum power transfer in an AC circuit depends on matching the load impedance to the Thevenin equivalent of the source network. The load draws current, and the circuit delivers power to that load. To analyze the current, the voltages, currents, network impedance, and load impedance are written in rectangular form. The average power delivered to the load comes from the square of the current multiplied by the load resistance. To find the condition for maximum power, the power is differentiated...

key terms and concepts

Learn how AC power is shared in series and parallel circuits, and why total complex, real, and reactive power stay conserved across a network.

AC Power in Series and Parallel Circuits | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

AC Power in Series and Parallel Circuits

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