# 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 ...
43 views

### 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 ...
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 ...
33 views

### 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 ...
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 ...
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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 ...
• 325
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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 ...
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### 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 ...
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960 views

### 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 ...
285 views

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1 vote
772 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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1 vote
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 ...
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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 ...
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5k 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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### 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 ...
1 vote
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 ...
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### 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 ...
• 3,814
1 vote
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 ...
• 684
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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1 vote
404 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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