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Questions tagged [apparent-power]

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

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Calculating Real Power Dissipation in a Series RC Circuit

Given circuit: simulate this circuit – Schematic created using CircuitLab Question: What is the real power dissipated in the resistor of the given circuit? My Solution: Note: I am calculating ...
Marco Moldenhauer's user avatar
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How do we calculate the current through two impedances in series by knowing the voltage of one and the impedance of the other?

I have a problem where I know the apparent power consumed by a Y-connected load and the line impedances, which I already reduced to work just with the line power (300kVA): the source and two ...
K. Rincon's user avatar
3 votes
3 answers
581 views

Why does reactive power lead to (I^2)R losses?

I read that reducing the power factor increases the current required in the lines (to deliver the same amount of useful work) and therefore increases the (I^2)R losses. Shouldn't the active component ...
gksingh.01's user avatar
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1 answer
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Troubleshooting for Power Delivery with Shunt Capacitor

I have been trying to derive an equation to find the power delivered to R(load) for the following circuit In order to do so I used voltage division Which simplified equated tp Then using the fact ...
Fernando Harley's user avatar
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2 answers
341 views

Why does the power factor of my fluorescent ballast seem to be impossible?

I have a ballast that's rated to run two 32 watt bulbs, which means (I think) that the working power is 64 watts. The line rating of the ballast is 0.5A at 120V, which means the apparent power (the ...
Robert M.'s user avatar
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2 answers
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What is the correct relationship between active, reactive and apparent power in non-linear AC systems?

I am somewhat troubled by the 'basic' formula that describes the relationship between apparent power (S), active power (P) and reactive power (Q) in AC systems. This formula is ...
JeromeBu1982's user avatar
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3 answers
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What is the real and apparent power of these steel cutters?

The US market model of this steel cutter is 120 VAC, 13.0 Amp. The NZ market model is 230 VAC, 1,100 W. I am trying to wrap my head around whether 1,100 W is the real power and so whether the apparent ...
Greendrake's user avatar
2 votes
4 answers
403 views

Toroidal core winding limitations

For traditional laminated EI mains frequency power transformer cores, the core dimensions and core material determine, for a given primary voltage and frequency, a minimum number of primary turns ...
Math Keeps Me Busy's user avatar
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1 answer
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How does negative (or export) kVAR and kW affect maximum demand charges?

I am trying to calculate enegy costs using data from an energy meter that provides me with halfhourly data points for the following 4 channels: Import kW Export kW Import kVAr Export kVAr and in ...
164_user's user avatar
2 votes
3 answers
285 views

Why is apparent power more important\relevant than maximum instantaneous power?

Given an AC circuit, the instantaneous power in the circuit can be determined by the formula $$P(t)=\frac {VmIm}2cos(\theta)+\frac {VmIm}2cos(\theta)cos(wt)-\frac {VmIm}2sin(\theta)sin(wt)$$ where \$ \...
Gary Allen's user avatar
17 votes
8 answers
6k views

Do circuit breakers trip on Apparent or True Power?

The thermal and magnetic protection for AC circuit breakers take into account both the timing and the magnitude of the AC current passing through. Does a standard circuit breaker trip on the current ...
Brethlosze's user avatar
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What is the significance of UPS output power factor?

A UPS's output rating is shown as 2000VA/1800W. I understand that the power factor here is 0.9, but the device or load I will connect to the UPS might have pf<0.9 or pf=1 (for light bulb.) From my ...
Md. Toufik Zaman's user avatar
1 vote
2 answers
750 views

What are the exact meanings of reactive and apparent powers? Do we say they are supplied or consumed?

(The following doubt is from the topic of Sinusoidal Steady-State Analysis of electrical circuits) I understand the meaning of real power - it is the average power consumed (or delivered) by an ...
Aditya's user avatar
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2 answers
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Relationship between power angle and real and apparent in ECO dataset

I am trying to parse the ECO dataset, which includes 1-second electric data collected from residential houses. Link to dataset: http://vs.inf.ethz.ch/res/show.html?what=eco-data But the relationship ...
alexander zak's user avatar
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Calculate 3 phases VA apparent power from DC load after bridge rectifier

In a tomatoes greehouse I try to power some high bay led light with 3 phases (400V between each phase: 230VAC*SQRT(3)). After 3 phases rectifier bridge i use the average DC line about 540V. All the ...
Teddol's user avatar
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6 votes
4 answers
1k views

Importance of the apparent power

It is said that, though only active power can actually do work, we have to consider apparent power to dimension the source. But what would seem important to me for that would be to know the maximum ...
Jonas Daverio's user avatar
2 votes
2 answers
2k 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 ...
N. Berg's user avatar
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1 vote
4 answers
5k 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 ...
DimP's user avatar
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1 vote
3 answers
625 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 ...
thece's user avatar
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1 answer
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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 ...
Pedro's user avatar
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1 vote
1 answer
832 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 ...
SeowZH's user avatar
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1 answer
64 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 ...
Oli's user avatar
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2 votes
2 answers
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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?
Kestis's user avatar
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3 answers
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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 ...
TryingToLearnMath's user avatar
1 vote
0 answers
132 views

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 ...
Brian Dohler's user avatar
0 votes
2 answers
777 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 ...
Michael George's user avatar
1 vote
3 answers
2k 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 ...
Jack's user avatar
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1 answer
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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.. √...
jNerd's user avatar
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1 answer
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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. ...
ejjman1's user avatar
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3 answers
247 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 ...
Michael George's user avatar