Questions tagged [magnetics]

Important to inductors, transformers, generators, motors, magnetic fields, inductive heating, magnetic storage, permanent magnets

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Why is the magnetic field inside a coaxial cable the same as it would be near a current-carrying wire?

Why is the magnetic field inside a coaxial cable the same as it would be near a current-carrying wire? Each side of the cable is conducting so shouldn't it be \$ \frac{I*μ0}{\pi*r} \$ because both ...
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3 answers
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Ethernet transformer

Can someone tell me what is the meaning of Open circuit inductance and why we need to take care while choosing magnetics? Also I have seen that, the turns ratio for selecting magnetics is 1:1 and must ...
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Phase Shifted Full bridge converter transformer design

I am designing a transformer for a phase shifted full bridge converter for voltage up conversion. My main concern is the efficiency, I am trying to reduce transformer loss to less than 5%. The total ...
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2 votes
1 answer
173 views

What are the differences between these ferrite cores?

The ER, EC, and ETD ferrite cores are presented in a datasheet but visually I don't see any difference between them. The search results also say the same thing.
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Calculating audio amp output impedance and other general questions [closed]

I'm 3rd year EE student and I am now doing a project where I'm basically making a supersensitive metal detector using solenoids. Solenoid has about 9 ohm resistance with inductance about 13 mH. ...
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1 vote
1 answer
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Types of air gaps

I read the Transformer and Inductor Design Handbook and I have some question would like to ask you guys. Why are the EE or EC cores shown in Figure 1-30B the bested suited? Why is only Figure 1-30B ...
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Voltage mode Ethernet PHY and Current mode Ethernet PHY

In the Ethernet PHY, we have two types. Voltage mode PHY and current mode PHY. Can anyone tell me the reason why the center taps of magnetics are shorted in case of connection to a current mode PHY ...
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Capacitors on center tap

This is a follow up to a previous question that I asked here Why do we add capacitors on center taps to the magnetics when connecting to an Ethernet PHY? Also what is the reason on why we terminate ...
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Inductance depends on the number of turns in a solenoid. Is this the case with reluctance as well?

The total flux (\$\Phi\$) through an solenoidal inductor of length \$l\$ and \$N\$ turns is proportional to the current through the inductor and the inductance \$L\$ of the inductor according to $$\...
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1 answer
19 views

GMR Sensor voltage output into magnetic field

I used a GMR sensor (Model AA003-02) inside a electricly adjustable homogenous magnetic field generated by a long coil. In other words the current is proportional to the magnetic field strength. ...
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1 vote
2 answers
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Is there any advantage if the PFC inductor is split in between +ve and -ve input line?

While doing the reverse engineering this is what I observed. The PFC inductor is having 8 set of pins , out of which 4 are shorted to input (+) and 4 are shorted to GND (input return). Obviously , ...
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Does skin effect increase the eddy current losses inside magnetic core?

From wikipedia -Ref1 The skin effect also reduces the effective thickness of laminations in power transformers, increasing their losses. From eddy current article in wikipedia-Ref2 "Eddy ...
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-1 votes
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Direction of vectors B and H - magnetic circuit

Does anyone know how to determine the direction of magnetic induction (B in the photo) and the direction of the magnetic field strength (H in the photo)? Is it taken as arbitrary or is there a rule? ...
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-1 votes
2 answers
47 views

Creating AC magnetic field with DAQ card [closed]

I'm a second year student in electrical engineering. For my project, I am working with magnetic nanoparticles and I need to set up an AC magnetic field. My plan is to build a solenoid (~1200 turns, 10 ...
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0 votes
2 answers
95 views

H-Bridge with highly inductive load

I am trying to understand the H-bridge, I have edited the circuit and followed the advice in this thread. Is this a good H-bridge design for excitation of the magnetic core which is highly inductive ...
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1 answer
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Difficulties in tuning magnetic levitation system on Arduino and MATLAB?

So I am dealing with a project that revolves around magnetically levitating an object below an electromagnet. I created a transfer function of it after making a mathematical model of it, and got this ...
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1 answer
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Construction of coupled inductors with lesser coupling factor

Most SMPS use coupled magnetics of various kinds. While designing buck/boost and their isolated versions, construction of the coupled magnetic element is straight forward. In many of these converters ...
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1 answer
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Which parameter determines the transformer size in a forward converter?

Upon enquiring for a 100W forward converter transformer, the vendor quickly suggested an EFD30 core. Does the size EFD30 represent the size of core as well as window area? As far as I remember from ...
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What is meant by EFD core?

What does EFD stand for in an EFD30 core size? Reference
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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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8 votes
5 answers
2k views

How do I build an electromagnet?

I want to make an electromagnet that can lift a paper clip off of the ground from a short distance (probably 7 to 8 inches). I naively thought of making an electromagnet as a simple task (because of ...
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Ethernet connection with discrete magnetics

I'm in the process of designing a carrier board for a raspberry pi cm4. Since I want to get everything as small as possible, I'm planning to use discrete magnetics for the ethernet connection. Looking ...
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Determining the type of magnet used in a hand-crank torchlight

I'm trying to design a DIY dynamo that recharges a 5V battery used to power some sensors. However, I am having some trouble with deciding on the arrangement of coils and magnets. Currently, I am ...
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0 answers
39 views

Jiles Atherton magnetic model for iron powder cores

I am currently designing several SMPS in LTspice. I am using the excellent work of Mr Bordodynov to model ferrite transformers. The Bordodynov Ltspice examples include a dataset for the JA model for ...
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Correct drift from IMU with magnetic sensor

Is it possible to correct the drift from the IMU by setting an external magnetic sensor as the reference point (zero) of the magnetometer in the IMU. For example, tracking the position of the wrist, ...
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0 votes
4 answers
111 views

Force on an Aluminium plate in a 1T field?

I am thinking of using a magnetic field to damp mechanical oscillations/noise in an Aluminium swing arm. The problem is that I do not even know how to calculate ballpark numbers for the effects I am ...
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0 answers
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Possibility of achieving magnetic levitation(Arduino) with just one solenoid and a ring magnet?

I am currently working on a magnetic levitation project and have been looking into all types of magnetic levitation. One particular video I found around the subject was this: https://www.youtube.com/...
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1 answer
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What is the meaning of below notations in flyback/forward transformer datasheets?

Flyback / Forward transformer datasheet How can I decipher the above diagrams? Does the inductance value represent magnetizing inductance? Why are there 2 windings (1-3 and 2-4) at primary side of ...
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1 answer
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Microwave Turntable Absorption

Do microwaves turntables absorb some microwave radiation when being used? I heard that they can act as a minimum load on the magnetron. If this is true, can I interchange microwave turntables? Edit: ...
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2 answers
119 views

Calculating number of turns an electromagnet has

The title, but can one calculate the amount of turns on a coil or find that out somehow? Because I purchased a 120m copper coil (originally intended on using it on another coil former before giving up ...
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5 votes
3 answers
836 views

Does a shielded inductor store less energy than an unshielded one?

As you can see in the image above, the magnetic field of the shielded inductor looks smaller, but does this mean the unshielded inductor can store more energy? (This all assuming the inductors are ...
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3 votes
2 answers
123 views

Does same pole magnetic field flow past each other in a iron core

In a textbook transformer design like the one in the image, if I put DC current on both coils making sure that they both have the same poles on the same side, for example, they both have north poles ...
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2 votes
1 answer
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Why doesn't magnetic power transfer use ferromagnetic cores in the coils?

One well-known fact is that putting a ferromagnetic material in an inductor will increase the magnetic flux and thus the inductance value. Wireless power transfer (WPT) happens through the magnetic ...
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4 votes
2 answers
618 views

Is it possible that north and south poles of a disc-shaped magnet change position over time?

[See update at the bottom] We build brushless DC motors of about 1 kW power at 48 volts. In order to drive the motor, we need to know the rotor position and, to do that, we fit a disc-shaped magnet on ...
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0 answers
42 views

What kind of inductor is used in the SMD pi-filter? Air core or ferromagnetic core?

What kind of inductor is used in an SMD pi-filter (LC) such as the LFCN-80? Air core or ferromagnetic core? Is it affected by external high magnetic fields (4 Tesla)?
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2 votes
2 answers
95 views

Loopy Artifacts in B-H Curves

Does anyone know the term for these artifacts in a B-H curve and their cause? I have no idea what to use to look up anything about them. These were obtained from the terminals of running a generator ...
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0 votes
1 answer
84 views

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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0 votes
2 answers
127 views

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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2 votes
1 answer
107 views

Why is the coupling coefficient constant for different airgaps in a coupled inductor on an EE core?

I recently made a coupled inductor on an EE core and wanted to calculate the coupling coefficient at different airgaps. The windings were each on their own outer leg and the airgap was inserted in all ...
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3 votes
1 answer
124 views

How lossy is a ferrite bead in its "capacitive" regime?

When using ferrite beads in spice, I often have the impression that they are not lossy enough compared to the real thing. In particular, the conventional model of RLC all in parallel is basically a ...
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2 votes
1 answer
68 views

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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0 answers
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Minimum Distance between two magnetic rotary encoders in an array : AMS [AS5048B]

I am planning to prototype with multiple AS5048B sensors. (Very basic: Magnets are horizontally placed over the IC that the IC can detect and give an angular reading). I plan to create an array of ...
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2 votes
1 answer
162 views

How to choose a common mode choke for ethernet?

I'm currently working on a design which contains gigabit ethernet. Due to some weird size constraints, I can't use a magjack or one of those transformer ICs, so I'm using discrete magnetics. I've ...
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1 vote
1 answer
210 views

Ethernet Magnetics, Discrete vs Integrated: Inductance Value

I recently made a change to an EtherCAT-over-Ethernet design, where I moved from using an RJ45 with integrated magnetics, to a low profile connector with discrete magnetics, due to size constraints. ...
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0 votes
1 answer
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Is there a way to know which magnet pole is facing the circuit?

I am not that much into magnetism, but I am facing the problem of defining the pole of the closest outer magnet it faces the circuit with. The magnet is completely out of control and might as well ...
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1 answer
78 views

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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1 vote
2 answers
139 views

How to solve magnetic circuits with windings in series?

Given the circuit in Figure 1, how would one go about finding V_EF? For me it is clear that V_AB + V_DC = 200 and that the current through windings AB and CD is the same. In addition, Φ_1 = Φ_2 + Φ_3....
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0 votes
0 answers
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BLDC waterproofing for submergance

I have modified a number of brushless DC motors to make them work underwater. The motors are the type with hall effect sensors. I did the following procedure on several motors, but the results have ...
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1 vote
1 answer
111 views

How to use Gigabit Ethernet Jacks with integrated magnetics for Fast Ethernet only

If have a Fast Ethernet PHY (LAN8720 for example) and want to use an Gigabit type of Ethernet Jack with integrated magnetics (RJMG201GMU1208R for example). Is it even possible/allowed and what would ...
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0 votes
2 answers
316 views

How do skin-effect and proximity-effect behave for flat-conductor power inductors?

Here is a Digikey search showing flat-conductor power inductors. And here is a picture of three power inductors found there: In this answer, by Rohat Kılıç, towards the end of his answer he explains ...
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