Questions tagged [phasor]

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Why is one current reading ~20% higher than the other two in a balanced high-leg delta load?

We are using eGuage watthourmeters to monitor the outdoor unit on five VRF systems powered by two different 3P4W 120/208V high-leg delta panels. The neutral is not connected to the outdoor units. We ...
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How can I solve the following phasor analysis question?

How can I solve part B? Obviously, since the two sources have different frequencies I started off by killing the voltage source (short-circuit) and then tried to apply KCL. My goal was to find the ...
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1 answer
77 views

Series RLC circuit - Phase difference between voltages across inductor and resistor is not exactly 180, why?

In phasor analysis we put inductor voltage along positive \$j\$ axis and capacitor voltage along negative \$j\$. So these two voltages are exactly \$180\$ degrees apart. But in simulation below, the ...
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3 votes
0 answers
121 views

How does a driving voltage affect an LC circuit?

I need help understanding how the drive voltage \$V_d\$ and the coupling capacitor \$C_d\$ in the circuit above affect the total energy of the LC circuit. The author arrives at the following equation ...
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2 answers
78 views

CT showing different reading at phase and neutral

simulate this circuit – Schematic created using CircuitLab I have attached a simplified version of my test circuit. When the current transformer is connected to the neutral side like in the ...
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1 answer
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Why use vector sum for calculating neutral current?

In a three phase system, we use a vector sum to calculate resulting neutral current. I don't understand why we use vector sum. The resulting neutral current is actually the sum of instantaneous values ...
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0 answers
47 views

Combined Space and Time Phasor Diagram of a Synchronous machine

Consider a synchronous generator with its electrical and mechanical angles between them In the left diagram δ is in mechanical domain but delta is also the electrical angle between Ef and Er in the ...
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1 answer
55 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; ...
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1 answer
74 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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2 answers
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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 ...
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1 vote
2 answers
97 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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2 answers
60 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, ...
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1 answer
100 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 ...
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1 answer
135 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 ...
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1 vote
1 answer
150 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 ...
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1 vote
1 answer
218 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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1 answer
255 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 ...
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2 votes
1 answer
3k 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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  • 301
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3 answers
164 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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2 answers
79 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/...
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1 vote
1 answer
39 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 ...
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1 vote
1 answer
71 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\$...
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0 answers
60 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 ...
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0 votes
1 answer
68 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 ...
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0 votes
3 answers
280 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'. ...
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  • 476
2 votes
1 answer
77 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 ...
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1 vote
1 answer
33 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!
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3 votes
1 answer
588 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{...
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  • 845
0 votes
1 answer
80 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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  • 187
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4 answers
96 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 ...
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1 vote
1 answer
104 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 ...
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  • 499
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2 answers
67 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 ...
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  • 3
0 votes
1 answer
164 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 ...
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  • 277
0 votes
2 answers
633 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 (...
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  • 111
0 votes
3 answers
86 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 ...
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1 vote
0 answers
41 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 ...
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0 votes
1 answer
290 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\$ ?
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2 votes
2 answers
522 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 ...
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2 votes
1 answer
1k 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?...
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  • 437
1 vote
1 answer
68 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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2 answers
63 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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  • 103
0 votes
1 answer
182 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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  • 125
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0 answers
276 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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  • 125
2 votes
2 answers
224 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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2 votes
5 answers
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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0 answers
183 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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0 votes
1 answer
52 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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2 votes
4 answers
237 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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1 vote
1 answer
411 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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2 votes
1 answer
2k 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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