Questions tagged [reactive-power]
Reactive power (measured in vars) is present in a system containing reactive (inductive or capacitive) components and can be either produced or consumed by different load/generation elements. Though "imaginary", the reactive power has great physical significance and is essential to the operation of the electrical system as a whole.
106
questions
0
votes
0
answers
36
views
Voltage magnitude estimation in DC power flow [closed]
I have a following engineering porblem. Consider a power flow problem for a power system and assume we have solved AC power flow for the whole network and obtained results. Now, imagine, I want to ...
0
votes
1
answer
20
views
Can reactive current in an AC circuit dissipate through another resistive load which is connected parallel in same circuit?
Two loads are connected in parallel to an AC circuit, one is inductive and the other is purely resistive. As per the nature of an inductive load, it will return the reactive power at end of each half ...
0
votes
2
answers
68
views
Where does the RF power go that is sent to a reactive portion of an antenna?
The impedance of an antenna can be lumped-represented as Rr (radiation resistance), Ro (ohmic resistance), XL (inductive reactance), and XC (capacitive reactance). The incident power from a generator ...
- 131
2
votes
2
answers
73
views
System of First Order ODEs for a Parallel RLC Circuit
I understand the behaviour of an RLC Circuit in Series can be modelled by the equation:
$$
L \frac{d^2Q}{dt^2}+R\frac{dQ}{dt}+\frac{Q}{C}=0
$$
Which can be represented by the system of First Order ...
0
votes
0
answers
50
views
How to find the active (real) power of source A of this circuit?
What is making difficult here for me is the fact that the two voltage sources are in series (or I think that they are). This is something which I did not face before. I am well aware of why Source A ...
- 121
1
vote
2
answers
64
views
Reversal of power through a electric transmission line
From my undergraduate classes I know that active power flows from the bus with the higher power angle \$\delta\$ to the bus with a lower power angle. If I want to reverse the direction of power flow I ...
- 13
0
votes
1
answer
59
views
Interpreting Changes in Software Energy Consumption During the Day: Seeking Insight on Patterned Peaks and Valleys
My group and I are currently studying the energy consumption of software as part of our master's degree in computer science. Specifically, we are looking at how to measure it accurately and interpret ...
0
votes
2
answers
76
views
How do we define which uses or supplies the power and reactive power?
There are two ideal voltage sources \$E_1= \angle 0°\$ and \$E_2=\angle 30°\$, \$E_1\$ and \$E_2\$ are not in phase, and there is an impedance \$z=5+0\mathrm{j~Ω}\$. The schematic is as below:
\$S_1=...
- 85
0
votes
1
answer
67
views
What is reactive power for a circuit at its resonance frequency?
Many sources I've read state that reactive power is important because it helps maintain voltage and magnetic fields in inductors, but in a circuit at its resonance frequency, the inductive and ...
2
votes
3
answers
128
views
Why does reactive power bounce back and forth between a source and load, while active power does not?
I am trying to understand the difference between active and reactive power. Reactive power is said to be "wasted" because it is constantly alternating between a source and load in AC power ...
- 197
0
votes
3
answers
177
views
Elliptic filter - implementation deviates from the design and simulation
I have designed a 7th-order elliptic filter using this online tool.
Cut off frequency - 15 MHz
Pass band ripple - 0.1 dB
Stop band attenuation - 70 dB
I've asked it to use tge standard inductor value ...
- 99
0
votes
0
answers
44
views
Calculating bus reactor efficiency in a high-voltage substation
Say I have time-series data-set containing the active power, reactive power, and voltage of a substation. I know the switching history of those bus reactors and obviously the MVAR capacity of the bus ...
- 101
1
vote
1
answer
89
views
Can I measure induction motor parameters with measurement tools?
I want to simulate a induction motor in ngspice so I need to model the induction motor as described here. I must calculate the model parameters as described here.
My questions are:
Can I measure the ...
- 11
0
votes
1
answer
55
views
Calculating the reactive current supplied to the grid by a generator
I have a calculation I don't really understand. Can someone help me to understand how this goes?
I have to calculate that I reactive power.
G = generator
M1 =tranformer
M2 = transformer2
johto = ...
- 1
-1
votes
1
answer
56
views
How can an ideal motor do any work when the average of instantaneous power over one cycle is zero? [closed]
The attached screenshot illustrates the instantaneous power delivered to a purely inductive load as a function of time. How does an ideal motor (or perhaps some other purely inductive load) do any ...
0
votes
0
answers
56
views
What happens if there is a reactive power imbalance in a large grid?
Consider the Continental Europe power grid.
Supposing there is a 1 GW of active power imbalance in the grid. This would lead to a frequency drop/rise in the whole grid at steady-state.
What happens ...
0
votes
0
answers
82
views
Reactive power fluctuation
We have 6 Caterpillar gas generators 3520c.
One of them when synches with the grid. Its kVAR fluctuates over wide range and the aux voltage too and the excitation volt and current. We checked AVR and ...
0
votes
3
answers
76
views
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 ...
- 445
-1
votes
1
answer
478
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 ...
- 3
1
vote
2
answers
163
views
How to calculate reactive power of a capacitor with a current waveform which consists of a sum of sinusoids?
Assume that there is a current which consists of a sum of sinusoids flowing through a capacitor with capacitance C.
How to calculate its reactive power?
It is quite simple with a pure sine wave but ...
- 1,547
4
votes
1
answer
423
views
Why does reactive power injection mitigate sagging grid voltage?
I understand that reactive power injection can be used by generators to support the grid voltage when sagging, but I’ve never understood why this works. I thought it could be charging transmission ...
- 298
2
votes
3
answers
267
views
Reactive power and eletro-mechanical analogy
Regarding this question, I will try to use the analogy of the differential equations $$F = m\frac{dv}{dt}$$ and $$V = L\frac{dI}{dt}$$ and $$w = \int Fv dt$$ with $$w = \int VI dt$$ to figure out the ...
2
votes
4
answers
78
views
Is the association of useful work to active power a convention?
I know that there are many questions about reactive power. What I am trying to understand is what is sometimes called useful work associated to active power, compared to no useful work for reactive ...
1
vote
3
answers
225
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 \$ \...
- 405
0
votes
1
answer
158
views
Short circuit analysis
Im given the next distribution line with a generator and a load
The generator is set at \$23\,kV\$ the line impedance is \$9.5\Omega +j19.055\Omega\$ and the aparent power is \$1.5MW+j2MVars\$ in the ...
- 495
1
vote
2
answers
430
views
What does mean if there is P+ and Q-?
If in a circuit there is real power positive and reactive power negative, what does mean in terms of power flow?
I undestand that the real power is produced in the generator/source and goes to the ...
- 495
0
votes
0
answers
51
views
What's the meaning of three-phase reactive power of a three-phase device in balanced sinusoidal conditions?
I'm trying to make physical sense of the three-phase reactive power (a.k.a. total reactive power) for a three-terminal or four-terminal three-phase device (e.g. an AC motor, an AC generator, a load) ...
- 969
6
votes
3
answers
471
views
Is reactive power periodic in nature? What is the exact difference between active power, average power, and real power?
Consider an RC circuit which is supplied by a sine source
$$v(t)=V_m\cdot \sin(\omega t)$$
The current through the circuit will be
$$i(t)=I_m\cdot \sin(\omega t+\phi) \\
\phi=\arctan \left(\dfrac{1}{\...
4
votes
6
answers
2k
views
Reactive power in AC circuit
What is meant by reactive power in AC circuits?
Power is joules per second.
Real power is the energy dissipated in the resistor per second.
What is meant by the reactive power? Does this mean the ...
- 1,070
5
votes
3
answers
2k
views
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 ...
3
votes
2
answers
112
views
Reducing reactive power by using a resistor
I have a school exercise that goes like this:
Voltage is 230V. Frequency is 50Hz. Inductor is 400mH.
How big of a resistor should be added with the inductor (in a series) to reduce reactive power by ...
1
vote
2
answers
255
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 ...
- 269
2
votes
3
answers
642
views
Using capacitors to reduce reactive power
I have been trying to understand the concept of reactive power in power systems. From what I have read so far, I understand that any inductive load like a motor needs some reactive power to function (...
1
vote
2
answers
675
views
Can battery inverters output reactive power?
This inverter manufacturer's Paper Bad Power Factor? – A reason to oversize your inverter mentions that "inverters can generate reactive power without using any active power."
Can battery inverters ...
- 11
0
votes
2
answers
46
views
In a transmission line, does the real current interact with reactive impedances?
simulate this circuit – Schematic created using CircuitLab
According to the diagram above, if real currents do not interact with reactive impedances, then reactive loads should not worry the ...
- 1
2
votes
3
answers
727
views
How does oscillation of reactive power take place between source and load?
I have come to read that reactive power is that power which is constantly oscillating between the source and the load.
Can anyone please explain this to me?
Suppose an AC source is connected with an ...
- 1,070
1
vote
4
answers
427
views
What is meant by average power in AC circuits?
I read that "The average power is the power averaged over a cycle or number of cycles."
I know that the average value of power for both active and reactive power is a constant number.
Buy I am ...
- 1,070
0
votes
2
answers
66
views
Instantaneous and active power in an ideal switch powered by real source and squared wave
This is a somewhat theoretical question, but one that has some impact on power theory.
The circuit in the figure is composed of a real DC source (with non-negligible internal resistance) and feeds a ...
0
votes
2
answers
287
views
What is the required VA rating of the transformer in this LTSpice power supply?
I have this circuit that I'm going to build, including the transformer. It is a simple power supply, with RC filters and one choke, I know all the voltages and currents.
Because I will design, wind ...
- 175
1
vote
4
answers
338
views
How does energy dissipates in a purely reactive circuit?
Suppose in a home, power factor drops to zero. It means that the circuit becomes purely inductive.
If the energy meter is connected at incoming power supply point,will the energy meter still keep on ...
- 153
2
votes
1
answer
328
views
Understanding equation for the quality factor of an RLC circuit?
In my textbook for a course on Circuit Analysis I came across an equation for the quality-factor of an RLC circuit. However, I don't quite understand their reasoning. The explanation that follows is a ...
- 209
2
votes
2
answers
526
views
Is there a mathematical proof that reactive power regulates voltage?
So after studying the power triangle and trying to conceptualize real power and reactive power, I seem to have come across a contradiction, at least in my own head. Most explanations disregard ...
- 143
0
votes
1
answer
63
views
Calculating reactive power on kVAr?
I think I understand how to answer this question but am missing how to do a certain part which stops me from getting their.
For this question this is all I know how to do.
cos-1(0.31) = 71.94°
...
- 19
0
votes
4
answers
595
views
What is the source of reactive power generated by the alternator?
We know an alternator or in general any source of energy does not generate energy but converts one type of energy into some other usable form.
An electric generator produces both real and reactive ...
- 21
1
vote
3
answers
3k
views
Why transformer is heating without load [closed]
I'm working as technician in computer store and I have a lot of scrap transformers . Most of them small and have 6-8 pins .I wonder, can I use them for my projects ?
If I remember correctly these ...
- 409
2
votes
1
answer
348
views
Adding an additional motor to a load
You have a 500kVA load with a power factor of 0.6 lag. You add an additional synchronous motor with an input of 80kW and max power factor of 0.8 leading.
Determine the reactive power and the overall ...
- 23
1
vote
1
answer
285
views
Example of Electrical Apparatus that draw leading VARS and Electrical Apparatus that draw lagging VARS [closed]
I understand that an AC inductive circuit will draw lagging vars while a capacitive AC circuit will draw leading vars (ELI the ICE man), but what are some examples of real-life electrical apparatus ...
- 11
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 ...
- 159
0
votes
1
answer
436
views
Reactive vs Real Power in DC-DC Converters
I don't understand which form of power, reactive or real, should be dominant in a maximally efficient DC-DC boost converter.
As the circuit charges the inductor, the current and voltage will be out ...
- 168
3
votes
2
answers
889
views
Simulate a motor with resistor and inductor
I want to simulate a motor with a resistor and inductor. It means I want to connect a resistor and inductor to 1-phase or 3-phase instead of a motor.
For achieving this goal I have to measure both ...
- 47