Questions tagged [magnetic-flux]

The sum normal component of a magnetic field passing through a surface.

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686 views

What exactly carries energy in a transformer from primary to secondary? [duplicate]

Suppose we have applied a voltage to a transformer with an open secondary, we will get a certain flux in the core and a certain voltage at the secondary depending upon the turns ratio. Now, suppose we ...
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Flyback power supply - 132 kHz radiated magnetic field issue

I request your expertise on a radiated magnetic field around 132 kHz (low frequency) on a Flyback power supply. I'm using the LNK3694 driver with a switching frequency around 66 kHz. Using a circular ...
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3answers
64 views

Why is the magnitude of mutual flux in a transformer independent of the current in primary?

Consider a transformer with no load, Given \$\phi= \phi_m \sin (\omega t)\$ \$e_1 = N_1 \dfrac{d \phi}{dt} = N_1\omega \phi_m \cos (\omega t)\$ \$E_1 = e_{1rms} = N_1\omega \phi_m \ \frac{1}{\sqrt{2}}...
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Why does peak torque increase on increasing air gap in induction motor?

I have been trying for a while to summarize the effects of increasing air gap in an induction motor with constant load. I understand that increasing air gap with constant supply voltage demands high ...
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14 views

Is the field distortion due to armature reaction constant in a series motor?

In a series motor the current in the field and armature windings are always equal. I'd expect that to mean that their respective fluxes always keep the same proportion. So, if this is true, does the ...
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2answers
108 views

In absence of leakage, what creates the angle between stator and rotor flux in an induction machine?

As per my understanding to produce torque from a machine, we need an angle between stator and rotor flux. In an induction machine rotor flux is created in response to stator flux, why is there an ...
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54 views

What is the Relationship between Magnetic Flux density and electric field intensity

I was given this question by a teacher and I have scoured the internet for a formula or solution to this question, all to no avail, the question says "in a certain region of space, the magnetic ...
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1answer
53 views

What is the standard procedure to design a Synchronous Machine?

I have Modelled an IPMSM based on the innovative idea i got. I have also decided on the rating of the machine, torque to be produced, Required Rated RPM, but after this i have so much doubt. whether ...
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27 views

Coil and PM Dimensional Ratios (BLDC)

I am in the process of laying out coils for a Axial Brush less Motor. My question is - without taking turns or power into consideration. Are there any design ratios - which should be attempted. When ...
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2answers
57 views

Confusion - ideal transformer on load

When there is no load connected to the secondary, E is equal to U, and no current flows in an ideal transformer. Now if we connect a load on the secondary of a transformer, the primary will draw a ...
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32 views

RF ferrite core inductor airgap magnetic field calculation

I was interested which formula I could apply to calculate the maximum field strength in an airgap located within an ferrite core, in my particular case I am looking at a "binocular" type ...
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4answers
329 views

Assigning a notion of voltage even when there is a changing magnetic field

In Walter Lewin's lecture, he finds depending on how you keep the lead of the voltmeter for a circuit in a changing magnetic field, you will measure different values]. This experiment is discussed ...
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2answers
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Solenoid : how dimensions ratio affects the magnetic field?

For a constant length of copper wire (with constant diameter), how can I calculate the most efficient solenoid diameter/length ratio ? (i.e. what ratio produces the strongest magnetic field, if the ...
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76 views

Kirchhoff's law for magnetic circuit

I have been working on this problem: The way I approached this problem is given (I used Kirchhoff's laws on Electrical equivalent of magnetic circuit) : I have two doubts here: My working does not ...
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1answer
37 views

Should the magnetic field outside a conductor be considered?

I've simulated a circular disc where a magnetic field is moving out of the page. The arrows in the picture represents the direction of its current density. I'm wondering, will the induced current ...
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Are there other quantities besides voltage and current that can be expressed as instantaneous values in AC circuits?

https://www.electrical4u.com/emf-equation-of-transformer-turns-voltage-transformation-ratio-of-transformer/ I got really confused when all of a sudden they treated flux with the time domain equation ...
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3answers
116 views

Why are Halbach Arrays useful in PM motors?

I understand how Halbach arrays strengthen the magnetic field on one side of the array. I also know that, in a permanent magnet (PM) motor, there is already a limit on the air gap flux you can design ...
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1answer
85 views

Slow solution of LTSPICE electric-magnetic model for transformers

I am trying to model a transformer using coupled electrical and magnetic circuits. SPICE has many advantages in assembling these circuits. I was able to model properly for an transformer with no load, ...
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3answers
155 views

Where to purchase the iron core for an electromagnet?

I want to build a strong elctromagnet. The design is very intuitive and simple, shown in the above figure. The metal core is in a cylindrical shape. The current design is 100 turns and 30 Ampere, with ...
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2answers
118 views

Behaviour of flux in DC motor

In given figure if we assume both sides (up and down) with equal number of coil turns (N each). And we wound(which generally we do in DC motor) coils such that they create flux and form a North-South ...
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0answers
25 views

Concept of a concentric-double-slotted axial flux permanent magnet machine (motor)

I am after a design of a permanent magnet machine which is very constrained in the axial direction, but basically unrestricted in radial one. I also need significant space for the shaft hole. The ...
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2answers
59 views

Basic question related to relay operation

Electromechanical relays are generally based on the principle​ that electromagnets(due to supply current ) attracts armature of relay which is made up of ferromagnetic material (because ferromagnetic ...
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2answers
70 views

derivative of current confusion

Say you have some B field from an alternating current, B(t)=B0cosωt. And using Faradays law, e.m.f. ε = turns of a coil × the time derivative of the flux of the B field going through the coil area. \$\...
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2answers
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The results of my magnetic flux data from voltage recorded

For my electrical engineering senior design I created an experiment to test magnetic flux (more voltage) through a receiving coil. There is a large sending coil with A.C. voltage and a small receiving ...
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1answer
143 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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Is mmf the same as the magnetic force?

In the following system, I created the following equation in terms of what I assumed to be the force acting on the movable object with a mass M. The reluctance of the core is neglected, so the total ...
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1answer
40 views

Transverse Flux Machine

For research, I want to build a levitation system that can levitate an aluminum sheet. With traditional 3 phase Induction engines you off course get levitation, but it isn't as stable as I want to. I'...
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1answer
35 views

What will be the graph of flux of coil 2?

In the following picture current is flowing through coil 1. Let's assume that current is increasing linearly in coil 1. Then emf induced in 2nd coil be will constant and having some negative value. ...
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Are bound current and eddy current independent of each other

I know that bound currents are due to magnetization of any material while eddy current is due to rate of change of flux through a metal so I wanted to know whether both currents are are independent of ...
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5answers
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Why does the current in a transformer's primary coil change when a load is attached to the secondary coil?

I don't really know if the question is suitable to be submitted here or in the Physics StackExchange. The problem is I don't quite understand this sentence from "Practical Electronics for ...
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2answers
317 views

What does the m symbol for magnetic flux mean? Why is it needed when the phi symbol exists?

For reference, I have read the Textbook of Electrical Technology by Theraja and I don't understand how it just uses the mass symbol as a symbol of magnetic flux in poles. Why is it any different from ...
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5answers
118 views

Power output of a transformer with many secondary coils, each coil of turn exactly equal to that of primary?

I am not a full fledged electrical engineer, and I couldn't find it on google, may be because I couldn't think of better combination of keywords. My question is, if we have a simple transformer with a ...
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1answer
66 views

Logic gate circuit to close when sensor signal turns ON and then OFF, but must ignore another ON?

I am trying to put a permanent magnet in a transformer between both coils, so that the transformer can utilize the flux from the permanent magnet by guiding its flux periodically. We have one primary ...
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1answer
49 views

EMP Halbach Array

Let's say I have a horizontal facing halbach array with equal north and south poles aligned one after the other, and a large circular gap in between them. If I fire an EMP gun through it, wouldn't the ...
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0answers
62 views

Bi polar pulse magnetizer controlled by arduino

Hello, I am trying to make a bipolar pulse magnetiser based on the pulse magnetizer design on instructables. I attached my circuit design as image. g1 and g2 terminals of the thyristors will be ...
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2answers
128 views

DC through an inductor

I get that the frequency is zero hence the voltage is consequently zero according to the the equations, but any current through a conductor should produce a magnetic field. I also understand that ...
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3answers
2k views

What happens if the secondary of an ordinary transformer is left open?

Let's consider a transformer. The ideal transformer equation is: $$\frac{V_1}{V_2} = \frac{I_2}{I_1}$$ Suppose the secondary is open (that means \$I_2 = 0\$): it will result \$I_1 = 0\$. How is this ...
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2answers
49 views

Does transformer's flux (due to load) need to obey Faraday's law

I believe I have a good understanding of a transformer. But I may have a misunderstanding somewhere that is leading to absurd conclusions. My overall understanding If we ignore all losses and look at ...
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2answers
93 views

Electromanetics question

Question : An infinitely long, very thin cylindrical conducting tube of radius b carries a uniform surface current Js = azJs(A/m). Find B everywhere. When r<b, it says that "In condition flux ...
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1answer
45 views

Why am I getting different flux densities?

I am trying to find the flux density at the top of the core. The current is known to be 2.5 A, the relative permeability of the core is known to be 800 H/m, and the flux is known to be 0.005 Wb. ...
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1answer
419 views

Do I need a diode to protect my ESP32 from a connected relay?

My ESP32 is controlling a relay which I switch on for 500ms (controlled through the internet). Do I need a diode to protect my ESP32 from voltage spikes when the magnetic flux collapses? I'm using ...
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0answers
36 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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2answers
327 views

why should we define "the magnetic flux is the dot product of the magnetic field and the plane area , instead of perimeter of the plane

When a uniform magnetic field \$\mathbf B\$ passes a plane at any angle, the magnetic flux \$\phi_B\$ is the dot product of the magnetic field \$\mathbf B\$ and the plane area \$\mathbf{a}\$,that is ,\...
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2answers
252 views

What is meant by AT/cm in transformer?

In a problem related to transformer loss I have found a line "AT/cm for a flux density of 1.2 Wb/m^2 in iron to be 5" I've searched in google for 30 minutes about what is AT and how it is related to ...
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2answers
304 views

How does magnetic flux affects the speed of a DC motor

I'm doing a high school physics project where we need to investigate the relationship between the speed and magnetic flux of a DC motor. We built a simple DC motor which basically looks like this, ...
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4answers
232 views

What happens to parts of induction cooker magnetic field not covered with the pan?

An induction cooker works like this. There's a flat coil of wire under the cooker surface which is connected to a source of high frequency AC and it produces an oscillating magnetic field with field ...
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1answer
2k views

Variable field magnet motor?

See the video in the following link: https://www.youtube.com/watch?v=olnXy-J48SY "Variable field magnet motor" How does this work and is it actually efficient?
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1answer
88 views

Why exactly does peaking of magnetization current occur in a transformer?

Initially assuming that the input current is sinusoidal. In a practical transformer, flux \$\phi\$ produced in the primary is not linearly proportional to the current \$I\$ through it. Due to ...
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3answers
190 views

Magnetic flux induced in toroidal core and conductor position

I was just reading Electric Power Engineering by Elgerd when I came across these statements about flux I couldn't fully understand: "By experiment, we can confirm a most interesting ...
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1answer
57 views

Is it possible to get Flux in a magnetic circuit with zero mmf?

From an Example that I stumbled upon on A.E. Fitzgerald's book on electric Machines. He assumed that there is flux in a circuit with zero mmf. Which I find very confusing. I would appreciate it if ...