Questions tagged [magnetic-flux]

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

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Disconnected wire still lit Tester turns on

I have multiple wires going through an electrical PVC conduit. Two phase wire carrying 220v AC of 1.5mm gauge. Two neutral wire carrying of 1.5 mm gauge. One wire for earthing (grounding) of 1 mm ...
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How does balancing currents within a cable or conduit cancel its magnetic fields?

I know the NEC requires all current carrying conductors of the same circuit to be included in the same cable or conduit [300.3(B)], but why? I think it is because the magnetic field generated by ...
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Does coil winding impact current direction? (Lenz Law)

When a magnet is moving toward a wire loop north-side first, the current goes counterclockwise according to the magnet's perspective, as shown in the image below from Wikipedia. Now, consider a ...
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Why can we say \$F=\phi R=NI=HL\$ according to \$V=IR\$?

Magnetomotive force is a quantity appearing in the equation for the magnetic flux in a magnetic circuit,this is the explanation of Magnetomotive force from WIKI : https://en.wikipedia.org/wiki/...
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Why is a DC motor's back EMF constant for a given RPM

I was trying to prove this mathematically from the definition of EMF being the change in magnetic flux over time. Starting with $$ \Phi=BAcos(\theta)$$ Then differentiate w.r.t time (assuming B field ...
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What happens to the permanent magnet flux of this synchronous motor?

Considering a synchronous motor with permanent magnets (1 pair) If there is a synchronous motor with permanent magnets and I was given the initial permanent magnet flux Y_mp = e0(at 15 rps) / w (at 15 ...
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Automatic metal detector using an Arduino

I did a project on automated metal detector, but I am not clear on the circuit. I built the circuit connecting a resistor to pin A4 on the Arduino, and a diode capacitor setup in series too. I don't ...
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Confused about the core flux waveform (and by extension the magnetising current waveform) of a current-fed push-pull DC-DC converter

I was going through the above converter and cannot understand how the flux in the transformer core changes (and by extension the magnetizing current). According to the text I'm reading, there are ...
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Electromagnet force and magnetic permeability

In a cylindrical core electromagnet, Magneto-motive force (MMF) = 613 At Magnetic strength (H) = 15345 At/m I am using an iron core with 10% silicon in it, so the saturation magnetic flux density of ...
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Audio Engineer needed to read 14-track magnetic tape

I have a 20 mm magnetic tape, with 14 channels. The data tape does not have any sound and format in which data has been stored on tracks is as follows. The picture of tape head is as follows. The ...
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Shielding AC magnetic field using cable shield connected to two grounds

I am currently reading a book about electromagnetic compatibility but I am confused about a section that talks about reducing the coupling between an external magnetic field \$ B_{ext}\$ and a circuit ...
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Does a certain cable arrangement that reduces the generated magnetic field improve shielding properties as well?

If I arrange a three phase cable via phase-split into an arrangement that reduces the generated magentic field, does this affect shielding properties as well? To reduce the generated magnetic field of ...
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Direction of magnetic flux of mutual inductance where coupling coefficient is almost 1

I've drawn the below diagram of the circuit. We will handle the system as the switch is closed . The coupling coefficient of the system is almost 1 I assumed \$~ L_{1} ,L_{2},M ~\$ are all positive ...
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Ampere's Law with dielectric

I am asked to calculate the magnetic-field-strength and magnetic-flux-density for different regions inside a coaxial-cable. I found Ampere's Law for that, but it uses \$\mu_0\$ , and the coaxial-cable ...
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Using a signal generator and power amp to supply >>240VAC to a coil

On Lenz's law, Wikipedia says: Faraday's law states that the EMF is also given by the rate of change of the magnetic flux where epsilon is the electromotive force (EMF) and \$\phi_B\$ is the magnetic ...
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Transformer Zero Flux Approximation

I have a question about a standard approximation made about the magnetic flux in transformer analysis. Using the magnetic circuit model, the sum of the magnetomotive forces in a transformer are: $$ \...
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How does mutual flux in a synchronous generator remain constant like in a transformer?

Given is the flux per pole of of a synchronous generator 1)Is it field/rotor flux per pole ? 2)The generated emf per phase is given by E=4.44Nfφ where φ is the flux per pole But from transformers, we ...
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Why does inductor core saturation depend on the temperature?

For example at room temperature (20ºC) the saturation current is 450mA and with 100ºC the saturation current is 350mA. What causes this? (Edit) The higher inductance with higher temperatures and lower ...
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Physics behind current direction in a transformer on HF

Let's consider the following schematics: According to the model, the current in the secondary winding always flows in the opposite direction than in the primary anywhere in 1-30 MHz range: Could you ...
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Why does the rotor magnetic field lag the rotor current by 90° in a 3 phase induction motor?

I was trying to understand load angle in electrical machines, generally denoted by delta, and I found out that while delta needs to be less than 90° in synchronous machine for steady state stability, ...
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What effect in the current will have the change of the diameter of coil but same length of coil and same magnetic flux?

First image is one coil with the large diameter and a magnet rotating to create current in the coil. Second image is the same set but the diameter of coil is smaller.
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Magnetic flux density in a point

This is a single phase copper line in the next configuration So its asked to find the magnetic flux density internal and external due \$I_{A}\$ and \$I_{B}\$ affecting the A cable and measured in ...
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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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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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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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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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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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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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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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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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4 answers
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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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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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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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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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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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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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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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2 answers
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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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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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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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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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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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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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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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1 answer
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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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5 answers
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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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