# Questions tagged [phase]

For questions about AC phases (e.g. three-phase systems) or phase in the context of waves, transfer functions, etc. Consider using in conjunction with related tags such as "three-phase", "transfer-function", etc., as applicable.

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### Why three-phase power? Why not a higher number of phases?

Is there a reason, beyond historical reasons, that three phases has become the dominant number of phases? I am aware of the advantages against one phase and two phase, namely the reduced amount of ...
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### Why 3 phase and not 1 phase power transmission?

Why does power transmission use three lines with three different phases? Why not three lines all in the same phase? Does it have to do with the alternators used for generating the power, or is there ...
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### Staying in Phase On The Grid

I have been an EE for over forty years and never did find out the right answer to this one.... How do power-stations and transformer switching stations ensure that the power they are feeding into the ...
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### Comparator: Noisy sine to square wave, how much phase noise?

In a circuit a comparator is used to convert a sinusoidal signal to a square wave. The input signal however is not a clean sine wave, but has some noise added to it. The comparator is supposed to be ...
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### How to find phase angle from transfer function

From the function: $$H(\omega) = \frac{1}{(1 + j\omega)(1 + j\omega/10)}$$ How is the phase angle obtained when it has multiple poles to get: $$\phi = -\tan^{-1}(\omega) - \tan^{-1}(\omega/10)$$ ...
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### Why do we use a diac for triggering a triac?

I mean, Wouldn't it be possible to give a gate pulse on triac directly? I have seen in many phase control application circuits like fan speed control,the usage of diacs to trigger a triac.
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### Transformer 220/380/440 V 24 V explanation

I have a circuit that uses three-phase electric power (without neutral). There is an old transformer in this circuit (see image). It converts 220-440 V to 24 V. The input has the handwritten numbers &...
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### Why doesn't the bypass capacitor cause phase shift in this oscillator circuit?

I am trying to understand oscillator basics. I thought I already understood how a capacitor works, but I still get confused about it. This circuit is an RC phase shift oscillator. I understand that we ...
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### Manual transformer winding - dots convention

I've already seen this and this. But I can't decide how to correctly wind a SMPS transformer. This is the transformer: I mantain the same turns direction (CCW if you look at transformer from the top)....
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### What does actually the "unravel branch wrap" option do to the phase plot in LTspice?

Below two Bode plots are identical just that in the second one the option "unravel branch wrap" is unticked for the phase plot: What does this option do to the phase plot?
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### Find the phase angle between two functions

Apologies if this is better suited for a mathematics forum, it's from my circuits textbook so I've decided to post here. Below is a practice problem from the textbook, with the provided solution. If ...
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### How is the gain/phase vs frequency measured for opamps?

Opamp manufacturers post graphs like these in datasheets: How is the data for this graph measured? Is it calculated using the mathematical model of an opamp?
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### Why do crystals have 0° phase shift at series resonance?

I am trying to understand the inner workings of crystal oscillators, but I do not understand why the current has 0° phase shift at series resonance. To my knowledge this is the equivalent circuit for ...
3k views

### How can current phase shift be 90 degrees behind voltage just "inside the capacitor" on an RC series circuit but be in phase in the resistor?

Imagine an AC source in series with an RC circuit. In this video, the instructor claims current will be 90 degrees behind voltage inside the capacitor but not inside the resistor or the whole circuit. ...
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### Why do some op amps' datasheet specify phase margin at open loop?

I am not able to understand what significance phase margin would hold in case of open loop. Shouldn't it be just phase? If it was loop gain I'd understand specifying phase margin to denote stability. ...
569 views

### About the torque-free charging operation

I and one of my friends are working on understanding the below context (paper link): The study provides an extensive overview of on-board integrated chargers for electric vehicles that are based on ...
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### Finding phase shift between the voltage and current

I am trying to find the phase shift $\phi$ of this circuit. I am using the formula: $$\phi = \arctan{\left(\frac{X_{L}-X_{C}}{R}\right)}$$ Substituting in the values: \phi = \arctan{\frac{2000\...
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### Can we short the neutral to earth (ground) at entry point of our home electrical supply?

Normally in our 230V power outlet, the voltages are as given below. Neutral to Earth - Less than 2V Neutral to Phase - 200V to 230V Earth to Phase - 200V to 230V But nowadays, after around 10 am, ...
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### Amplitude noise vs Phase noise

I've been reading that Phase Noise dominates in frequencies close to the carrier, while Amplitude Noise is more dominant in higher offsets. Could someone explain this?
11k views

### 240 V split phase and 240 V single phase

All right, I don't get it. I tried and tried, but I just don't understand. I have a dozen questions about this so somebody just pick one out all of these, I don't care. What's inside a North American ...
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### Why multiple series resistor on single phase metering reference design with HLW8012 and BL0937 IC

We need to implement energy monitoring in our smart plug. We are considering 2 ICs HLW8012 and BL0937 for this purpose and following are their reference designs in their data sheets. I am trying to ...
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### How to measure phase accurately using LTSpice?

I am trying, and failing, to measure phase in LTSpice. I've used the suggestion here ...
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### How can I create two ac signals with a voltage controlled phase offset?

Is there a fairly straightforward analog circuit (resistors, capacitors, transistors, etc) to generate two sine waves of the same frequency and introduce a relative phase offset between them? So I'm ...
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### Can a phase margin become bigger than 180° and is this bad?

I have a wrong mental model about phase margin in control theory. I see that a phase of -180° is bad. If my input is a sine wave and I have negative feedback, which has a -180° phase shift, the ...
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### Understanding Phase frequency detector logic

I have one of these common digital phase lock loops which compares the frequency and phase with a VCO (local oscillator) via a phase lock loop. I failed to understand why Figure (2) (A) and Figure (2)(...
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### Why does it work to connect between phase and ground, if the electrical circuit is not completed or closed?

Maybe it's a silly question about electrical installations. I'm not talking about rules, protections or if it is correct to do what I'm going to describe. I just want to understand why it works. For ...
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### Run heater on two powerlines, where the second line is switched according to the main line

I got a water heater which is rated 6kW. The "heating element" consists of 3 heating elements that are connected in series for 1-phase usage. I would like to run two of those heating elements on one ...
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### Is group delay the same as the delay of a certain frequency?

I know that group delay is the delay of the envelope, or the derivative of the phase with respect to $\omega$. What I want to know is what exactly happens in the time domain. For instance take the ...
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### Detect Phase Difference 360 Degrees

Let's say I have two sine waves that are both DC offset to have no negative values, the measurement I want is the phase difference between these waves. When researching I've only seen detectors that ...
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803 views

### 3-phase to single-phase power - motor

I have a circuit with a motor that uses 3 phase power supply. The circuit includes a control relay (like this ), (L1 L2 L3 NO A1 and T1 T2 T3 - A2) and a thermal relay (like this) the A indicator ...
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### Circuit To Measure Phase difference

Is there any classical analog circuit to measure the phase difference between two analog signals ( especially sinusoidal signals )? I want to measure the phase difference between two sinusoid signals ...
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### Snubber Circuit working

How does snubber circuit work in phase control circuit of Single Phase AC Motor? I have tried to know the causes but I was confused with RC circuit function with this phase control circuit.
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### Magnitude calculation of filter

I am working on a problem for a given transfer function given below and am having trouble calculating the magnitude and phase of it. The problem is specifically that I do not know what method to use ...
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### Suitability of standard-gain pyramidal horn for UWB signal

Objective I'm interested in evaluating the suitability of a standard-gain pyramidal horn for an ultrawideband (UWB) signal. However, I've had difficulty finding reliable information about the phase ...
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### Does guitar pickup absolute polarity matter?

I have a Telecaster which has a phase issue in the middle position, because the bridge pickup is wired backwards (the hot output to the ground). This hot grounded output is also used to ground the ...
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### Can I use any capacitor for a 2 phase AC motor?

So recently I got my hands on an old pump motor, unfortunately the connection diagram is missing. I have already determined this is a 2 phase motor, and that in order to make it work I need a motor-...
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### How are phase values able to capture motion from video?

I know that the phase spectrum contains most of the structural information about the image. But I want to know more about importance of phase spectrum related to video signals. I have read that ...
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### Phase relationship of multiple Fractional-N PLLs with same reference clock

I think I understand the general operation of PLLs in the case where a single reference clock generates a single output clock. Once the PLL is locked, there is a deterministic relationship between the ...
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I've got a signal that consists of 2 square waves at 2 different frequencies in the kHz range, about 10 Hz apart. I need to determine the relative amplitudes of 2 different known frequencies and I was ...
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### Approximation of a Non Ideal Differentiator

simulate this circuit – Schematic created using CircuitLab The above circuit is a differentiator, the op amp is assumed to be a single pole op amp, that is $A=\frac{wt}{s}$ The transfer ...
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### Triangulation with Single Tone FM TX and Three RX using Phase Detection [closed]

I'm looking for some IC and frequency suggestions to accomplish the following task. Modulate a tone onto a carrier and continuously broadcast this signal toward an array of three receiving antennas(...
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### Whether phase congruency and phase coherence terms are same or different?

I am studying the importance of phase in signal.Can anybody explain what is phase congruency ? Also,I am confused between terms i.e. phase congruency and phase coherence. Whether phase congruency and ...
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### About power dissipation of capacitors and inductors & I-V phase difference

For instance, The Art of Electronics (by Horowitz & Hill) states that ideal capacitors cannot dissipate power, even though current can flow through them, because the voltage and current are 90° ...
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### Phase modulation for binary data - higher frequency harmonics?

I've recently learned about PSK and QAM. I first came across it in this youtube video (timestamped), and my understanding for how it works has remained the same as what is shown in that video. (I also ...
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### The distribution of phase angle between identical zero mean Gaussian random signals?

I am trying to solve the 2013 paper set by ISRO for electrical engineers. I was hoping to get some clues on how to approach this problem - No 22. random signals which have gaussian distributions will ...
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### Make FTDI 2232D do SPI mode 1 properly? Data seems 1/2 clock cycle off

This capture by a Saleae Logic Pro 8 (v 1.2.18) shows the result of transmitting (MOSI data) 0x20 0x11. Unfortunately it is interpreted and shown as ...
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### Is there a way to measure the Phase Shift between the input and the output voltages related by the equation: $V_o = V_i(a+jb).$? [closed]

Say $V_i$ is an input voltage, and the output voltage is given by $V_o = V_i(a+jb).$ Is there a way to measure the Phase Shift between these input and output voltages?
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### Why does the tank circuit of a Colpitts oscillator produce 180° phase shift?

I would like to understand how a Colpitts oscillator works. This link says that the tank circuit of a Colpitts oscillator produces 180° phase shift. I don't understand how a combination of a coil and ...
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### How can I mathematically show that multiplication of j will cause a phase shift?

I have a simple question that I cannot seem to wrap my head around. let's say I have a function Asin(wt), if I multiply a '-j' by this function to get: -jAsin(w*t), I have been told that this is ...
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