Questions tagged [phasor]
The phasor tag has no usage guidance.
147
questions
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1answer
48 views
Phasor angle calculation
In this example, for Vo it first says it is lagging by -134.8 degrees, however when then calculating actual Iin, the angle for Vo becomes -138.4.
I'm wondering if -134.8 is a typo, and if it isn't; ...
0
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1answer
57 views
Does Clarke transformation convert scalar quantity to vector quantity?
Current is a scalar quantity, is it converted to vector quantity using Clarke's transformation?
If it is correct, I would like to know how transformation converts from scalar to vector?
Thanks and ...
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2answers
35 views
Phasorial notation
In the phasorial notation (of a voltage or current, for example), should i use the peak value of a sinusoidal wave or its effective value (rms)?
I ask this, because i get confused after reading some ...
1
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2answers
47 views
KVL in the frequency domain - Why is the sum of phasors 0 and not just the real part of the sum?
In many proofs of Kirchhoff's voltage law for the frequency domain, the time-domain KVL is originally used and then the time-dependent part (\$e^{jwt}\$) is removed, leaving only the real part of the ...
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2answers
38 views
About simulating an ac circuit in Pspice
Firstly, It's not homework. I already know the answer. But I couldn't see sinusoidal waves to calculate phase of voltage(V0) across the capacitor. Response of capacitor is look like damping. However, ...
0
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1answer
49 views
Phase angle of sine wave (confusion)
Usually, phasors are represented by Acos(ωt + φ) where φ is the phase angle.
Using this convention, we need to convert sin(ωt) into cos(ωt - 90) to get its phase angle like this thumbnail on a YouTube ...
1
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1answer
69 views
Differential Equations vs Phasor vs Laplace
I've just read a book on basic circuit theory and I'd like to understand the pros and cons of each analysis method.
Time Domain
Usually ends up in differential equations for reactive circuits.
Gives ...
1
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1answer
71 views
Band stop filter RLC circuit frequency response
Assume we have an $ RLC $ circuit as described in the picture
This should be a Band-stop filter. But somethings bother me in my calculations. This is my calculations for the frequency response:
Using ...
1
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1answer
62 views
Explaination on phasor diagram for RL circuit?
This is the phasor diagram which I had drawn from the value of phase difference(deg) from MULTISIM. I'm a bit confuse here... shouldn't by theory, when inductance is increase, thus the degree for Vl ...
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1answer
78 views
Why voltage in capacitor lags behind the source voltage in RC circuit?
Voltage across the capacitor lags behind the current through capacitor as we know. But why the voltage across the capacitor lags behind the source voltage in this circuit ? Similarly it is found that ...
2
votes
1answer
679 views
Converting from time domain to phasor domain?
If I have a voltage source of a circuit
\$V_s(t) = 8\cos(24\pi*10^9t-60^{\circ})\$ (V)
and I want to convert it to the phasor domain would it be this?
\$8e^{-j60^{\circ}}\$?
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3answers
101 views
IQ modulation and phasors: which first?
Do we use IQ modulation because quadrature signals are a good physical implementation of phasors - or is it the other way around?
To elaborate a little:I'm having a hard time getting a clear ...
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2answers
43 views
Why is the phase angle in the summation of the phasors the negative arctan?
I was reading a textbook and came across the following
$$
\\I_1 = Ae^{j0} = A
\\I_2 = Be^{-j\frac{\pi}{2}}
\\\bf{I} = I_1 + I_2
\\If\ A=10\ and\ B=20
\\|I| = \sqrt{A^2 + B^2}
\\\angle I = -tan^{-1}(B/...
1
vote
1answer
36 views
Can AC harmonic quantities be expressed as a sum of phasors of different frequencies without confusion?
https://www.electronics-tutorials.ws/accircuits/harmonics.html
The problem with AC harmonics is that each term has a different frequency, being a integer factor of the first frequency. I was wondering ...
1
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1answer
58 views
What am I doing wrong in finding the phase angle of power?
Consider a voltage supply \$V\angle \phi_1\$ and a circut with impedance \$Z \angle \phi_2\$.
Now the Apparent power(\$S\$) is given by: $$\bar S =\frac{(\bar V)^2} {\bar Z}$$
Thus phase angle of \$S\$...
0
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0answers
47 views
is it possible for the phase difference between voltage and current to exceed pi/2 in a RL circuit?
I did an experiment where I made a RL circuit. My IV was resistance and DV was phase difference between voltage and current. To find the phase difference, I took the difference (Δt) between time when ...
0
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1answer
56 views
Phase-shift a Broadband Time-Domain Function
Suppose we have an operator \$A_\phi\$ which phase-shifts a sinusoid by \$\phi\$:
$$A_\phi[\cos(\omega t)] = \cos(\omega t + \phi)$$
In phasor domain, \$A_\phi = e^{+j\phi}\$ is a complex constant.
I ...
0
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3answers
165 views
Why can't circuit breakers close across a large phase angle difference?
In power systems I understand that breakers have mechanisms preventing their closing if they detect the phase angle (and voltage) across them to be too large. This is usually called a 'sync check'. ...
2
votes
1answer
67 views
RMS values and Phasors
I need to solve these two exercises but I really have no idea where to start.
How should I proceed to solve this kind of problems?
I tried to find something on my teacher's files but haven't ...
1
vote
1answer
28 views
How do I transform this sinusoid in phasor?
If it is a signal like this i(t)=5*sin(100t-pi/3)A, I know how to transform.
But how do I do this e(t)=2-√(2)*sin(10t+pi/4) ?
I meant I don't know what to do with "2-"
Thanks for the help!
3
votes
1answer
214 views
How to calculate rotor flux of the three phase squirrel cage induction motor?
I have a three phase squirrel cage induction motor with given parameters (stator winding connected in delta)
nominal power: \$P_n = 22.4\,\mathrm{kW}\$
nominal stator voltage: \$V_{sn} = 230\,\mathrm{...
0
votes
1answer
69 views
RC circuit - phase current
I have a simple RC circuit as below :
I'm trying to visualize current curve and voltage curve (Vout and I(R1)) vs Vin using LtSpice and I obtain the result below:
It's OK that the Vout is leading ...
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4answers
75 views
can I also use phasors/concept of impedances for non sinusodial signals?
I know that phasors are great to solve circuits driven by sinusodial input signals but I was wondering if I can incorporate phasor concepts(like impedance) to circuits driven by input signals not ...
1
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1answer
74 views
Complex impedances of capacitors/inductors in the phasor domain
I'm trying to verify the complex impedances of passive components in the phasor domain (not s-domain). Take for example the inductor, whose element law is \$ v = L \frac{di}{dt} \$. Assuming a complex ...
0
votes
2answers
53 views
Resonant frequency and maximum signal width
I've seen resonant frequency being defined as the point where the input signal is in phase with the output signal (So reactance/susceptance is 0).
However conceptually, teaching material seems to link ...
0
votes
1answer
81 views
Finding the total impedance and voltage across open terminals
The question that I'm trying to solve is the following:
In the circuit shown below, what is the total impedance in ohms across the open terminals? What is \$v_{T}\$ if \$v_{L}\$ is 80 vrms?
This is ...
0
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2answers
408 views
Calculating Phase angle from instantaneous voltage
For background info I am an EE/CE that is 10 years out of school and has since worked writing firmware and dealt mostly with digital communications and signals, so now I am having to reach back to my (...
0
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3answers
78 views
How can current be in different phases in the same wire at the same time?
We know that either in ideal or practical transformer in no-load condition, the exciting current has two components Ic(core loss component) and Im(magnetizing component). Now since the same current ...
1
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0answers
38 views
Rotating magnetic field discrepancy
This may be a noob question
Lets consider a balanced 3 phase supply namely
\begin{align}
R&= V \sin(x)\\
Y&= V \sin(x-120)\\
B&= V \sin(x+120)
\end{align}
At a neutral point we would ...
0
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1answer
217 views
How to calculate voltage across capacitor C1?
If the voltage
\$v_I = \frac{jωC1R3}{1 + jωC1R3}*Vs \$
does that mean the voltage across the capacitor would be equal to \$v_S - v_I\$ ?
2
votes
1answer
324 views
Integral of phasor
Say \$v(t) = V_m\cos(\omega t+\phi)=\Re[V_me^{j(\omega t +\phi)}] = \Re[Ve^{j\omega t}]\$,
where \$V_me^{j\phi} = V\$.
Integrating gives
\$\int\limits_0^t v(t)\,dt = \Re\int\limits_0^t Ve^{j\omega ...
2
votes
1answer
782 views
Polar form vs phasor form?
I know that polar form has two parts. Amplitude and angle but
What is difference between polar form and phasor form of complex numbers? Or phasor form just includes amplitude form of a complex number?...
1
vote
1answer
59 views
Current divider usage
I was solving this exercise where I have to find the current through each of the circuit branches. Sorry if the image is a bit confusing but after determining the current I I used the current divider ...
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2answers
60 views
Finding 70% Voltage Point
Let \$v_1\$ be the input AC voltage and \$v_2\$ be the output AC voltage such that gain \$\dfrac{v_2}{v_1} = \dfrac{A+jB}{D+jE}\$ where \$j = \sqrt{-1}\$. How should I find the 70% point (the point ...
0
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1answer
177 views
Help on (another) triphasic exercise
Second this week... But was it easy I wouldn't be here...
A problem asked me to identify the diagrams from this picture:
The following are the correct answers, acording to the test developers.
a. ...
0
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0answers
186 views
Relation between phase angle and current direction
In a triphasic system (any), is there a way to tell if the current is entering or leaving a phase/line/load just by the angle of the phasor of the source ?
In the following picture we can see the ...
2
votes
2answers
133 views
Derivation of telegrapher's equations
I'm currently going over the derivation of the telegrapher's equations shown here, but there's a step that I'm not fully grasping.
I think I can follow some of how you get from eq.3 to eq.5:
If the ...
2
votes
5answers
2k views
Does an oscilloscope subtract voltages as phasors?
I want to measure two voltages on an oscilloscope. They are not in phase. I want to know the magnitude of the voltage difference. The oscilloscope has an in-build math function to subtract the ...
0
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0answers
167 views
Superposition theorem with phasors [duplicate]
Can someone explain the superposition theorem step by step when applied with phasors (AC circuits)?
I think books and websites mostly include examples of how to solve something with superposition but ...
0
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1answer
51 views
Complex Amplitudes and Exp'l Increase/Decrease
The following are quotes from a textbook,
If S(t) is represented as a rotating phasor, the angular frequency
of the phasor can be thought of as velocity at the end of the phasor.
In particular ...
2
votes
4answers
161 views
Is the frequency response of a circuit only valid for steady state (phasors)?
This is my first post. I just finished a course about advanced circuit analysis techniques (the content was taken from textbooks by Sadiku, Hayt and Irwin.) As you know, phasors are used to solve ...
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vote
1answer
323 views
Transformer's Primary and Secondary Voltages
In general, which is the phase relationship between the primary and secondary voltages of an ideal transformer? Does it depends on the dot convention?
2
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1answer
1k 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
44 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
33 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
554 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} $$
Where Vc(t) is the capacitor's voltage at ...
0
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5answers
480 views
Why can phasors be used simplify getting instantaneous power from instantaneous curent and voltage?
If instantanoeus power is p(t) and instantaneous voltage and current saying for a resistor are v(t) and i(t), then p(t)=i(t)*v(t). But if you convert v(t) and i(t) to their respective phasors and ...
0
votes
1answer
76 views
Is my calculated capacitor sign correct?
I have the following circuit where I would like to obtain an analytic expressions for the value of \$Cs\$ and \$Rs\$ only kowning the phasors \$\bar Vina\$ and \$\bar Vinb\$ there displayed, I don't ...
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2answers
199 views
Phasors: why is my book using sines?
When I learned phasors I learned we passed from sinusoidal to phasor this way:
$$\sqrt{2} V\cos(\omega t+\phi) \rightarrow \sqrt{2} Ve^{j\phi}$$
However I'm now studying for a book that does this:
$...
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2answers
103 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 ...
