Questions tagged [phasor]

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48 views

What is the current in this circuit? (Using Phasors)

simulate this circuit – Schematic created using CircuitLab I have attempted the question with the following working although the answer does not match the real answer, are there mistakes in my ...
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1answer
54 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
57 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 ...
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33 views

Phasor voltage drop clarification?

Upon reading this pdf about voltage drop calculations : https://pdhonline.com/courses/e426/e426content.pdf I came across page 30 which shows the image down below. I am a bit puzzled on their ...
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1answer
171 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. ...
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0answers
57 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 ...
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2answers
90 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 ...
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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 ...
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0answers
67 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 ...
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1answer
49 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 ...
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0answers
42 views

Phase voltage of a three-phase source with impedances knowing the line voltage

How can we determine the phase voltage of a balanced triangle three-phase source when impedances are present in that source and knowing the line voltage? When we only have voltage sources, the line ...
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4answers
76 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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1answer
133 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?
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1answer
237 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 ...
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1answer
42 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
29 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 ...
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3answers
211 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 ...
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3answers
107 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 ...
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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 ...
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2answers
146 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
75 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 ...
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0answers
64 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 ...
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1answer
126 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 ...
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4answers
463 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 ...
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2answers
65 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
127 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 ...
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1answer
51 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 ...
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1answer
345 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/...
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1answer
87 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....
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1answer
357 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 ...
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2answers
114 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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1answer
50 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 ...
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3answers
179 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 ...
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1answer
890 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 ...
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1answer
94 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 ...
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2answers
2k 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
71 views

Phasor representation

How did we separated/broke down this phasor expression?
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2answers
96 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 ...
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1answer
550 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 ...
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1answer
254 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 ...
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1answer
111 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 ...
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2answers
158 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
147 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 ...
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3answers
77 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. ...
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1answer
104 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 ...
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0answers
47 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,...
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2answers
171 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 ...
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1answer
103 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"
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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 ...
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1answer
324 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 ...