Questions tagged [magnetics]
Important to inductors, transformers, generators, motors, magnetic fields, inductive heating, magnetic storage, permanent magnets
0
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2answers
33 views
Determining magnetic flux density of a closely wound toroidal coil
I am using David K. Chengs's Fundamentals of Engineering Electromagnetics book. In chapter 5/question 5.2, there is a given closely wound toroidal coil, and it asks what is the magnetic flux density ...
0
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0answers
31 views
Why does the receiver coil voltage of this WPT circuit decrease at varying rates as the distance between the transmitter and receiver coil changes
The circuit below is a circuit that wirelessly transfers power via inductive coupling. I used a digital oscilloscope and measured the output voltage of the receiver coil at varying distances between ...
1
vote
2answers
74 views
How does a hall effect wheel speed sensor work?
I have been researching how a wheel or crank speed sensor works in vehicles and am having a hard time finding a hard truth.
I think I understand how it works simply. That the sensor detects a change ...
1
vote
1answer
38 views
Difference series resonant and LLC DC/DC converter
What is the exact difference between a series LC resonant converter and an LLC converter. From a topological perspective, they seem to be exactly the same. I believe that for an LLC, also the ...
9
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3answers
2k views
Does this experiment show that Kirchhoff's Law hold when there's a changing magnetic field involved in a circuit?
In this video, the electrical engineer and youtuber Mehdi Sadaghdar (ElectroBOOM) disagrees with another video from professor Walter Lewin.
Basically, professor Lewin shows in an experiment that if ...
0
votes
1answer
41 views
Proper connection of choke coil in ethernet magnetics
I need to use the medical ethernet magnetics by Pulse HXU6200NL (it is the only 2MOPP medical-certified PoE magnetics I can find). These are of the rather common transformer/choke coil topology. My ...
1
vote
2answers
100 views
Double ethernet magnetics for a passive medical application
I am designing medical data acquisition equipment that requires moderately fast data transfer. As part of the design we are using a custom 100BASE-T PoE architecture (and cabling) to the data ...
1
vote
2answers
32 views
Optimizing magnetic field force of a coil
For a personal project, I've done a redesign of Samy Kamkar's MagSpoof project. Basically, it is possible to use an electromagnet, h-bridge, and microcontroller to trick a magnetic card reader into ...
2
votes
1answer
120 views
What is the purpose of perpendicular “smaller” magnets in between the main magnets in a rotor of a motor? had never seen this before. Do they help?
I am trying to build my own generator at home for fun, I saw on a video in youtube https://www.youtube.com/watch?v=YsSm65DAcCg where the guy placed smaller magnets in between the main magnets of the ...
0
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0answers
26 views
Measuring a magnetic field using a loop
I am trying to use a loop to measure oscillating and pulsing magnetic fields.
Using Faraday's Law
(N - number of coil turns, B - magnetic field, A - area of coil, t - time)
I should be able to ...
0
votes
3answers
197 views
Wireless power transfer - Inductive vs. resonant mode
When talking about how wireless power transfer is done, the standards (e.g Qi) distinguish between inductive and resonant mode. (Link)
They claim that when the units are in very close proximity it is ...
1
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0answers
53 views
Cable Side and Physical Side of a PoE Magnetics
I am reading the datasheet of PoE Magnetics. I am not able to understand which side belongs to cable side and which belongs to ...
1
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0answers
55 views
Dolby HX PRO implementation on existing tape recording deck
I'm experimenting the implementation of Dolby HX PRO's IC into an old stereo Fostex tape deck to improve high frequency and headroom capabilities.
HX PRO works as a dynamic processor with the BIAS ...
0
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0answers
49 views
Pulsed a magnetic field, what would be a suitable way to pulse a high current?
I would like to pulse a magnetic flux of up to 25 mT, for an experiment. I would like the pulses to be as short as possible 60-70 ns.
I have a solenoid, 10 cm in length, 5 cm diameter with 7 turns, ...
1
vote
0answers
50 views
How strong is the field of a magnetic strip on a credit card?
How strong is the field of a magnetic strip on a credit card? In other words, at the typical distance of a read head, say 0.001" how strong is the magnetic field from the stripe?
(Note this is NOT a ...
-1
votes
2answers
131 views
Detecting very small magnetic movements
I am looking for techniques and methods to detect very small linear magnetic movement caused by a bar magnet. Imagine a bar magnet that can produce yaw and pitch but with extremely low frequency and ...
1
vote
2answers
67 views
Is there a way to make an experimental magnetic head?
I recently had a magnetic stripe on my bank card fail and I was curious to find out the exact nature of the corruption which would require scanning the surface of the stripe and determining its ...
2
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0answers
116 views
In an induction cooktop, what happens to the coils resistance when there is no pot? Does it vary between pots? How does the appliance respond?
An induction cooktop (or an induction rice cooker) uses a copper coil with a high-frequency alternating current going though. The magnetic flux heats any iron-alloy pot placed above.
But what ...
1
vote
2answers
40 views
Can I create a continous gap in iron powder cores?
The iron powder core material, as you may know, has a continuous air gap in its structure. However, do you think it is possible to add a continuous air gap (for example 1mm) to the iron powder cores?
...
0
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1answer
60 views
Toroid coating got scratched
Will there be any performance effect if the torroid coating gets scratched?
2
votes
0answers
120 views
Magnetic field in the air gap of a transformer core
I am trying to calculate the magnetic field, Hg, and have been looking these formulas. I would like to know if I am on the right track, as something is not working out for me.
From these with a ...
1
vote
0answers
38 views
Alternate formulation for the Neumann formula
I'm currently learning about the Neumann formula for the calculation of the mutual inductance between thin current filaments. However, for future purposes I want to find an alternative formulation of ...
1
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0answers
40 views
Can a CM choke saturate due to the leakage inductance?
On a 3-phase common-mode choke, if the three currents sum to zero, then it will theoretically never saturate.
I understand that the leakage inductance stores energy in the core.
Can the three phases ...
0
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3answers
45 views
Magnetic field direction
How do I know the direction of magnetic field produced by a bar magnet, assume a electron present side to the magnet ?
0
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2answers
227 views
Increase the pulling force of a solenoid with a permanent magnet [duplicate]
I have a number of solenoids I would like to use in a project. The problem is that they're not quite powerful enough so I've been trying to come up with ways to increase the their pulling force ...
0
votes
1answer
48 views
Calculating the magnetic flux density in cylandrical coordinates near a neodymium disc magnet
I am looking for an analysis of a disc magnet, I have heard there are 2D analaysis and 3D. Could someone point me in the right direction of a paper or some academic text on the matter.
I don't mind ...
0
votes
1answer
32 views
90 degrees phase shifted magnetic fields
If we have a closed magnetic circuit with two primary coils and one secondary coil wound on it. The primary coils are wound such that unlike poles are adjacent. Both primary coils are using rectified ...
1
vote
2answers
61 views
Do MRI magnets oscillate due to parasitic capacitance?
Moved here from SE Physics.
Do MRI magnets oscillate during charging or even during persistant mode due to parasitic capacitance? What problems can this cause?
I am planning a low temp ...
2
votes
3answers
112 views
Why is the magnetic field around a bar magnet represented by iron filings?
Why would we use iron filings to display a magnetic field interaction and then teach this as the unaffected field of a magnet?
Iron affects the field itself. This is analogous to an observer ...
0
votes
1answer
57 views
Simple Stepper motor for my experiment?
To graduate (Grade 12 or Year 12), I need to do an self-thought experiment in Physics. I decided to do something about stepper motor because I learned that they use this type of motor for robot arms.
...
0
votes
3answers
122 views
Circuit approximation of Induction in guitar pickups
I was trying to learn the way basic guitar circuits work, the other day, and I stumbled upon a thing that I couldn't fully understand.
According to this site, a simple guitar circuit can be made as ...
1
vote
2answers
309 views
Metal detector coil SHIELDING?
Many designs of coils, of metal detectors, are shielded (Faraday shield).
Should this be used in a gravity-fed detector (like the sketched one)?
What's the shield for?
NOTE:
The coils are arranged ...
1
vote
0answers
46 views
Calculation of stray magnetic field from substation transformers
Say I want to assess the magnetic field attributed to some substation equipment and the cables in the substation area. Calculating the contribution from the cables and busbars are for my purposes done ...
0
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0answers
57 views
Toroidal Inductor magnetic field question
I need confirmation of my understanding of the magnetic field induced by a toroid inductor.
What think is:
The magnetic field B or H encircles the vector lines of A... A being the curl B.
A ...
2
votes
1answer
115 views
Tranformer Output waveform
If input to a transformer is square/triangular, draw its output voltage waveform.
This problem was asked in one of my recent interviews, please help me with this problem.
0
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0answers
161 views
Relationship between brushless coil inductance and back EMF as a function of phase angle
In general, does the inductance across the coils of a brushless motor have the same waveform as the back EMF? That is, if back EMF is sinusoidal, should I expect the inductance to be sinusoidal [with ...
0
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0answers
54 views
Falling Marble Sensor
I'm really building a sort of Rube Goldberg machine that students will assemble in order to guide a falling ball down through a series of gates/openings, where I need to detect when they're successful ...
1
vote
2answers
133 views
Saturating magnetic field in an inductor without heating
I am building an RL series circuit with a toroidal inductor that I am winding on my own. The toroid is made of steel (low carbon, I believe, but not 100% sure) and has about 280 turns of 22 gauge wire....
0
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0answers
48 views
Understanding maxwell's equations
I'm trying to use the fundamental maxwell's equations to see how this expression was derived:
∇⋅ (E⋅ E+ c^2 B⋅ B)
= − ∂/∂t(E⋅B-E⋅B)+ 1/ε
(B⋅J - J⋅B)
c is 1/sqrt(ue).
I have found the cross product ...
0
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1answer
53 views
Strong H fields: electronic items susceptible to thier damaging effects and how to shield them
This is another question related to magnetic fields. I'm trying to determine the thickness of copper foil that would be required to shield common electronic items from H fields of about 133 A/m over ...
2
votes
1answer
63 views
Energies of the fields in a plane wave, attenuated and unattenuated
This is a combination of two of my previous questions (question 1 and question 2) which are related.
I'm trying to learn both how energy is carried in the electric and magnetic components of a plane ...
0
votes
1answer
166 views
EMI difference between Ferrite (powdered iron) and Iron
In an EMI application where I'm applying a snap on style ferrite core around a cable. What's the difference / benefit of the typical powdered iron type and just using a similarly sized piece of iron ...
0
votes
2answers
84 views
Energies carried by electric and magnetic fields in plane waves
This is a newbie question. I'm trying to understand what I think must be a very basic concept with an obvious answer, but I want to be sure.
Do plane wave electric and magnetic fields of equal ...
0
votes
3answers
64 views
The electric and magnetic components of far field EMR and shielding thereof
This is a newbie question. I'm pretty sure of the answer, but I would like confirmation. I found this thread in this forum that came close to what I was looking for, but I think my question is ...
0
votes
2answers
85 views
Magnetic Locks mods [closed]
What about magnetic locks? Two questions..
Does armature plate need be exact size as magnetic mate? Id like to get a bigger one milled so i dont have to use lasers to check perfect alignment. ...
0
votes
1answer
61 views
magnetic hall effect sensor
I'm currently working on building a density based traffic light model. I want to use the magnetic hall effect sensor to detect the number of the cars passing, so the idea that I have is to place the ...
1
vote
0answers
34 views
Any deleterious effect from very strong, close magnets on NiMH cells over time?
This question probably isn't a perfect fit for this SE, but I did find this question: Will placing a strong magnet near my electric skateboard Li-Ion Battery pack damage or discharge it?
This is a ...
1
vote
1answer
558 views
Ethernet magnetics - PHY side center tap isolation
I am designing a PCB that will use a Microchip KSZ9896C 6-port Gigabit Ethernet Switch. In the datasheet (section 7.2) they state that :
"the four transformer center tap pins on the KSZ9896C chip ...
0
votes
1answer
80 views
Why transformers Secondary magnetizing inductnace and Secndary inductace are Not Considered while doing filter calculation for output ?
Why transformers Secondary magnetizing inductnace and Secndary leakage inductace are Not Considered while doing filter calculation for output ? Why most transformer datasheet only mention ...
1
vote
1answer
135 views
What is the relationship between field strength and efficiency in a DC motor?
This refers to a DC motor with permanent magnets.
What is the relationship between the efficiency of the motor and the magnet field strength?
