Name: power factor and ac load behavior
Uploaded: 2024-07-08T13:19:54.000Z
Duration: 1 min 11 s
Channel: JoVE

O fator de potência é a razão entre a potência ativa e a potência aparente.
É determinado pela diferença de fase entre a tensão e a corrente, que surgem devido à presença de elementos reativos no circuito.
Uma analogia pode ser feita com um copo de café, onde o café simboliza a potência ativa útil, e a espuma representa a potência reativa, que, apesar de não realizar um trabalho real, é utilizada em determinados aparelhos.
O custo cobre todo o vidro. Para obter o valor máximo, a potência reativa deve ser reduzida para aproximar o fator de potência da unidade.
Para uma carga puramente resistiva, a tensão e a corrente em fase produzem um fator de potência unitário, onde a potência aparente é igual à potência ativa.
Para uma carga puramente reativa, o fator de potência é zero, o que implica que a potência ativa é zero.
Entre esses extremos, o fator de potência está à frente ou atrasado. Um fator de potência principal indica que a corrente lidera a tensão, implicando uma carga capacitiva.
Um fator de potência atrasado significa que a corrente está atrasada em relação à tensão, indicando uma carga indutiva.

fator de potência

O fator de potência é definido como a razão entre a potência média (ou ativa) e a potência aparente, conforme ilustrado pela relação

<img alt="Equation 1" src="/files/ftp_upload/15122/15122_Equation_1.svg" style="height: 30px;">

O termo entre parênteses, (θ_v - ​​θ_i), é referido como ângulo do fator de potência, pois representa o ângulo cujo cosseno produz o fator de potência. Se V representa a tensão na carga e Ⅰ significa a corrente que flui através dela, o ângulo do fator de potência é igual ao ângulo da impedância da carga. Essencialmente, o fator de potência é o cosseno da diferença de fase entre a tensão e a corrente, bem como o cosseno do ângulo da impedância de carga.

Da equação acima, pode-se inferir que o fator de potência é o multiplicador da potência aparente para produzir a potência real ou média. O valor do fator de potência varia entre zero e um. Ao lidar com uma carga puramente resistiva, a tensão e a corrente estão em fase, resultando num ângulo do fator de potência (θ_v - ​​θ_i) = 0 e um fator de potência = 1. Isto indica que a potência aparente é igual à potência média. Para uma carga puramente reativa, (θ_v - ​​θ_i) = ±90o e um fator de potência = 0, tornando a potência zero. Entre esses dois extremos, diz-se que o fator de potência é adiantado ou atrasado. Um fator de potência adiantado sugere que a corrente precede a tensão, indicando uma carga capacitiva, enquanto um fator de potência atrasado sugere que a corrente segue a tensão, indicando uma carga indutiva. O fator de potência impacta significativamente as contas de eletricidade que os consumidores pagam às suas concessionárias.

Fator de Potência

O fator de potência é a razão entre a potência ativa e a potência aparente.
É determinado pela diferença de fase entre a tensão e a corrente, que ...

Education

JoVE Core

Electrical Engineering

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Unit 1

Unidade 1

AC Steady State Power

Potência de Regime Permanente CA

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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 case, the power factor angle is 0 and the power factor is 1, so apparent power equals average power.

A purely reactive load gives the opposite extreme. The phase difference is ±90°, and the power factor is 0, so the power is zero. Between these limits, the power factor can be leading or lagging. A leading power factor means current leads voltage, which points to a capacitive load. A lagging power factor means current follows voltage, which points to an inductive load.

Power factor also matters in everyday electricity use. It affects the electricity bills customers pay to utility companies. Understanding it helps explain why the phase relationship between voltage and current is important in AC circuits.

Power Factor and AC Load Behavior

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...

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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...

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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 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 power factor links voltage, current, and AC load behavior. Explore phase difference, leading and lagging loads, and why it affects electricity bills.

Power Factor and AC Load Behavior | 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

Power Factor and AC Load Behavior

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