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Questions tagged [apparent-power]

Total power in an AC circuit, both dissipated and absorbed/returned

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68 views

What is the direction of negative reactive power

In a R+1/(jwC) load (AC)voltage lags current with θ degrees. Reactive power Q is negative because sin(θ) is negative. My question is how can a capacitive load deliver power to the source wich is ...
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4answers
187 views

Active Energy, Reactive Energy or just Energy?

I understand the concepts of active power, reactive power and apparent power. I am not sure I am getting the complete concept about the respective energies. I am using an energy monitor to record ...
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3answers
140 views

Active (P), Reactive (Q, D) and Apparent (S) Power from Instantaneous Power (p)

I am having a difficultly with producing \$S, P, Q \$ and \$D\$ from Instantaneous Power \$p(t)\$. Let's say that both voltage and current are clear sine waves. Then: \$p(t) = Vsin(ωt+φ_V) \cdot ...
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289 views

Why does line current equals the total apparent power divided by 3 times the phase voltage?

In this circuit with frequency of 50hz and line to line voltage of 400 V why is the current \$ I_A = S_t/3V_P\$ I don't understand the logic behind since there is one Delta connection, I understand ...
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1answer
345 views

Apparent power calculation of different loads for transformer sizing

Let's say we have two electrical loads and we would want to calculate the total apparent power in order to size the transformer to supply the demand. I'm currently confused between which two ...
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59 views

Power reading in different places

Currently, I have a software which able to read voltage, current, active power, apparent power and reactive power from appliances which I assume the readings should be approximately same even though I ...
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2answers
2k views

Does reactive power of induction motor vary with load?

I know that the power factor of an induction motor varies with load and is very low at no load and high at full load, but does the reactive power vary as well? If so, how much can it vary?
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3answers
219 views

Is the average of instanteous power equal to real power?

simulate this circuit – Schematic created using CircuitLab I'm trying to understand if the average of instantaneous power is equal to real power. My reasoning is that the reactive components ...
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0answers
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Measure 3-phase Power with Lecroy Waverunner

Please note that experience with a Lecroy Waverunner Oscilliscope is most likely required to answer this question. I'm attempting to measure the power draw of a brushless 3-phase motor with a Lecroy ...
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2answers
233 views

Why do these equations prove that power factor is constant for all circuits in case of sine wave?

I know that I'm missing something but I don't know what I'm missing. Power factor is the ratio between real power and apparent power. So, I will get the equations of real power and apparent power ...
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3answers
1k views

calculating the average power using the oscilloscope

I am trying to measure the real power of an inductor, and in the manual it is said that I have to connect a resistor with low resistance to the inductor and then see the voltage difference between the ...
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1answer
1k views

How to derive apparent power formula for three phase AC system?

I know that the total power output of a three phase system is √3 EI cosØ Where E and I are the line voltage and line current. Now my question is how can one derive the apparent power equation i.e.. √...
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1answer
224 views

Power In does not Equal Power Out

I have the following setup: 480V, 200A service fed into PWM Drive, Drive output going to 1000kVA step up transformer (8.4 ratio) feeding a 2380V/53A 3phase induction motor. The motor is UNLOADED. ...
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136 views

Why are Watt's more common than VA's?

I know that VA is the unit of apparent power (combination of real and reactive power) and Watt is the unit of real power only. So, I think it is more precise and accurate to express electrical power ...