Questions tagged [phasor]
The phasor tag has no usage guidance.
1
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1answer
51 views
Phasors and Fourier Transform
I have always been told that for a sinusoidal variable (for instance a voltage signal), the fourier transform coincides with the phasor definition, and this is the reason why the analysis of ...
0
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1answer
32 views
AC signal analysis: Voltage dip (amplitude dip) at time = 0
I'm working on a series RLC problem where the input voltage is a sinusoidal function for all time. The catch is, for t < 0, the sinusoidal function is of greater magnitude than t >= 0. There is no ...
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0answers
27 views
What is the DC component of the sum of phasors?
I am preparing for the written test conducted by IISc Bangalore for admission into their graduate program. I happened to come across a sample paper from 2016, I think.
I am struggling to understand ...
0
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3answers
97 views
How does one relate an RC circuit's time domain solution to phasors?
It seems to be a given for phasor analysis that the voltage across a capacitor can be defined as follows:
$$ V_{C}(t) = V_{A}\cos(\omega t + \phi)\tag{1} $$
Where Vc(t) is the capacitor's voltage at ...
0
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3answers
70 views
Why can phasors be used simplify getting instantaneous power from instantaneous curent and voltage?
If instantanoeus power is p(t) and instantaneous voltage and current saying for a resistor are v(t) and i(t), then p(t)=i(t)*v(t). But if you convert v(t) and i(t) to their respective phasors and ...
0
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1answer
74 views
Is my calculated capacitor sign correct?
I have the following circuit where I would like to obtain an analytic expressions for the value of \$Cs\$ and \$Rs\$ only kowning the phasors \$\bar Vina\$ and \$\bar Vinb\$ there displayed, I don't ...
1
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2answers
139 views
Phasors: why is my book using sines?
When I learned phasors I learned we passed from sinusoidal to phasor this way:
$$\sqrt{2} V\cos(\omega t+\phi) \rightarrow \sqrt{2} Ve^{j\phi}$$
However I'm now studying for a book that does this:
$...
0
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2answers
64 views
Output of AC op amp circuit has unknown superimposed signal on top of expected output signal
I am trying to find the voltage gain of a certain ideal op amp circuit with a sinusoidal input. However, when I simulate the circuit, the output shown seems to be my calculated output but with a ...
0
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0answers
33 views
Actual direction of phasor current - Power Calculation
I am trying to calculate the complex power in this circuit.
I used nodal analysis to find Vc, and the voltage at the top of the 2H inductor (=3.13<177.8 V_RMS). I did the math for all elements in ...
0
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1answer
98 views
Determine the power dissipated in W in the 5 Ω resistor [closed]
simulate this circuit – Schematic created using CircuitLab
Excuse me for my really bad use of the schematic feature I just didn't know how to switch to the phasor domain. Anyway, I'm asked to ...
3
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4answers
167 views
Phasor vs Vector vs Space Vector
I wonder what is the difference between a Phasor, a Vector and a Space Vector? A phasor is also a rotating vector in space then it means that a space vector is same as a phasor? Also by definition a ...
1
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2answers
58 views
Time to Frequency Transform - Where are the Initial Conditions?
In a circuit with sinusoidal source and charged capacitors and inductors we have initial conditions:
$$u_{C}=u(0)+\frac{1}{C}
\int_{t_{0}}^{t}i(\tau)d\tau$$
$$i_{L}=i(0)+\frac{1}{L}
\int_{t_{0}}^{t}...
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4answers
104 views
Sinusoids represented using Euler's formula notation, confusion
EM plane waves are represented using the equation (ignoring amplitude) $$E(x,t) = e^{j (wt - kx)}$$
They are also represented in this form: $$E(x,t) = \cos(wt - kx)$$
I want to get the electric ...
0
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1answer
39 views
Synchronous Generator EMI
In the attached image below, I don't understand the text and phasor diagram that I have highlighted in yellow.
Why does the induced emf on the armature winding lag the magnetic flux of the ...
0
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1answer
123 views
How to calculate current from a phasor?
I'm just working through some textbook exercises and have been stuck on this one for a while.
The question is:
The current in an AC circuit is represented by the phasor \$I = I_0 e^{j(120\pi t + \pi/...
1
vote
1answer
43 views
Odd step in derivation of phasor Telegrapher's equations
In the derivation of the phasor form of the Telegrapher's equations (in "Fundamentals of Applied Electromagentics" by Ulaby), there is a step I'm not following:
When going between eq. 2.16 and eq. 2....
2
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1answer
251 views
Working of a Doubly-Fed Induction generator (DFIG) in wind turbines
I am unable to understand how a Doubly-Fed Induction generator works (in Wind Energy conversion system)? I do not understand how the reactive power fed into the stator interacts with the rotor so as ...
0
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2answers
84 views
Simple phasor problem with AC
Simple problem that I can't solve.
On this AC circuit, find the current read by ammeter \$ A_3 \$ (the one in series with the resistor) given that \$A_1\$ reads 4A and \$A_2\$ reads 3A, assuming ...
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0answers
21 views
Topological observibility in OPP problem
I have a short question about observability analyzing constraint in optimal PMU placement problem in power system. Observability analyzing has two method: numerical and topological. Most of papers use ...
0
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1answer
44 views
State estimation in power system [closed]
Regarding state estimation in electrical power grid, does the voltage phasor magnitude at each bus(P-Q bus and P-V bus) considered as a static state variable or a dynamic state? I am a little bit ...
0
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3answers
77 views
For an ideal Capacitor, when is the current leading and when is the voltage leading by 90?
Say I have a purely restive load as a reference in parrallel with an ideal capacitive load. I know that the current through the capacitor is said to be leading by 90 degrees. Specifically though, what ...
0
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1answer
520 views
Confusion with interpreting leading and lagging concepts for given electrical quantities
I have a confusion interpreting the lagging leading concept when it comes to time plots.
I think in phasors I can see which one is leading or lagging. For example in the below phasor diagram:
How I ...
1
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1answer
82 views
Why can't phasors be equated to a sinusoid?
I'm having trouble understanding why a phasor for an AC sinusoid, let's say voltage (represented as Vrms/_50° for Vsin(ωt + 50°) to a current, for example) cannot be equated to the sinusoid in ...
2
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2answers
1k views
Voltage drops are greater than source voltage. How is it possible?
This circuit was given in my textbook. The source voltage is only 10 Volts, but the individual voltage drop across resistor and inductor are 6 Volts and 8 Volts respectively, which is greater than the ...
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1answer
60 views
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2answers
82 views
ac phasor voltage between capacitor and inductor higher than source voltage?
I've just learned about phasors and I am very confused about this. Take this circuit as an example:
simulate this circuit – Schematic created using CircuitLab
So by what I've learned, All I ...
6
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1answer
403 views
Fourier series of output voltage
I've been practicing some Fourier series questions and then verifying my answers by generating an equivalent graph on MATLAB and comparing it with the graph generated by PSpice in simulating the same ...
0
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1answer
186 views
dq transformation using phasor quantities
3 phase AC quantities can be either represented in the Time domain or the phasor domain. It is also possible to transform 3 phase quantity to alpha-beta or d-q-0 reference frame using Clarke's ...
0
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1answer
97 views
Can someone show this problem for this example step by step
Plot the magnitude and phase of the following complex functions:
G(w) = 1/(1+jw)
We never went over this in lecture but apparently I have homework on it. Looks pretty simple but just don't know ...
2
votes
2answers
145 views
How to use phasor algebra to solve for capacitive reactance?
I have an RLC series circuit.
Voltage supplied by volatage source as a function of time: \$V(t) = 230 \sin(\omega t+\pi/4)A\$.
Current in circuit as a function of time: \$I(t)=10\sin(\omega t - \pi/...
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0answers
130 views
Phase difference between two waves from wave equation
I need to calculate phase angle between
$$i_1 = -4\sin(377t + 55) \hspace{0.2cm}\quad \mathrm{and}\quad \hspace{0.2cm} i_2 = 5\cos(377t - 65)$$
I need to determine which one is leading too.
My ...
1
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3answers
75 views
Determining V and I from limited data
I am the recipient of an incomplete set of data for several 120 volt, single phase, AC drive systems driving induction motors under various loads. The measurements were taken at the AC voltage source. ...
0
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1answer
85 views
Criteria for considering transmission line effects due to phase delay
Below drawing illustrates a transmission line where the source voltage is:
Vs(t) = V0 x sin(ωt)
After reading some texts about the subject, I concluded how to decide whether one must consider ...
1
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0answers
45 views
Calculate current on tri-phase circuit with parallel resonance
I'm struggling with the following circuit.
data are:
E1=10V (three phase 120°)
\$\omega\$=20 rad/s
XC=-10
R=10
XL=10
About VGO I calculate the tri-phase voltage as
$$E=\frac{10}{\sqrt{3}}=5,...
1
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2answers
157 views
Intuitive meaning of setting determinant = 0 in oscillator analysis
I'm reading a book on oscillators at the moment and the author is explaining a method of analysis based on the system determinant.
Given the following generic FET tuned oscillator arrangement:
and ...
0
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1answer
80 views
constant independent of time, meaning of this line?
can someone please explain last paragraph in the Picture that i have uploaded, in layman's term specially this phrase "constant independent of time"
0
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1answer
57 views
Clarification needed regarding average power through a load
The question for the following circuit was to find the average power through the load \$ Z_{L} \$.
The first and second image shows that \$ I_{2} \$ and \$ V_{2} \$ were found. I assumed that the ...
0
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1answer
253 views
Reference phasor(or quantity)
So I learnt about phasors and phasor representation this week in college. I noticed that in every example problem that we did, one phasor was chosen as reference and the angle was taken as 0°. My ...
1
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1answer
75 views
Other than Voltage, Current and Power, what else can a Phasor describe?
I've always thought of just these 3 things that a Phasor can describe -- the magnitude and phase of the sine function of these 3, vertically centered at 0 and of the same frequency.
Are there more?
0
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1answer
52 views
Nodal Analysis of Circuit
Given this circuit, we want to find V(t) or the equivalent D node circled.
I set up the nodal analysis equations in the phasor domain as follows, with a super node at the dependent source.
However,...
1
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1answer
64 views
Phasor with source
220 muF stands for \$220\cdot10^{-6} F\$. Sorry for putting it that way.
The question is to find the equivalent impedance Z with a frequency = 50 Hz. I know how to find all the Z of the capacitor and ...
0
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2answers
209 views
Finding voltage across an RL circuit
Given the following circuit diagram
I know that in order to find either values, I can apply...
or ...
But I am having some trouble understanding how I can get rid of the imaginary term j in ...
0
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2answers
54 views
Modelling a power supply system
I understand that for a RL based circuit connected to an AC supply, the impedance for the inductor is jωL and also I need to find the net resistance of the load model which I have derived to be (R*jωL)...
0
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1answer
588 views
Negative voltage regulation in transformers
If a capacitive load is connected at the secondary coil of a transformer, a leading current flows and in turn, the secondary voltage is higher than the referred primary voltage. I learned that partial ...
0
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2answers
151 views
Drawing phasors using waveform
I have the question "Using the waveform given, draw a phasor for the following point"
So here is the waveform:
Here is the answer to the question, however I am not sure how this is achieved. I have ...
0
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1answer
42 views
Phase of this AC circuit
What will be the phase of the current trough the coil:
I think that I can find it using:
$$\arg\left(\underline{\text{I}}_\text{L}\right)=\arg\left\{\frac{230\sqrt{2}e^{\frac{\pi\text{j}}{2}}}{\left(...
0
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1answer
113 views
Determining whether a load is reactive and its reactance type by the phasor (phase angles)
I have been given the following question:
A single-phase load is supplied by a single-phase voltage source. If the current flowing from the load to the source is 15∠-135° A and if the voltage at ...
2
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3answers
790 views
Why do phasors work with s-domain transfer functions?
In as few words as possible, here is my question:
Why can we get the output phasor by multiplying the input phasor by the s-domain transfer function evaluated at the (complex?) frequency we're ...
1
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1answer
65 views
Motor and Phasor
A group of induction motors with a total of 480 kW and a power factor of 0.8 lagging is to be partially replaced with synchronous motors of the same efficiency but leading power factor of 0.7. As the ...
2
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4answers
307 views
Art Of Electronics - How does the phasor diagram explain away 3db verses 6db confusion
simulate this circuit – Schematic created using CircuitLab
Hi,
In the follwoing two images, I am having a problem seeing the confusion the author is talking about and more importantly how he ...
