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Questions tagged [magnetics]

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

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37 views

Is there risk to using magnets on an enclosure that would have 1-2A wire assemblies leaving the enclosure

Would there be a reasonable risk to using magnets to close a large enclosure panel which has 3 motor drivers with wire assemblies that leave the enclosure to drive stepper motors? The motor drivers ...
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25 views

Confusion regarding the right hand thumb rule

I am confused regarding the use of the right hand thumb rule . There is two use cases for this rule : 1- The first when the thumb points in the direction of the current the fingers points in the ...
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1answer
36 views

Shape of a core for use in a solenoid

I am currently designing an electromagnetic accelerator meant to accelerate a spherical nickel-plated NdFeB (neodymium) projectile along a circular tube, in a similar manner to a particle accelerator. ...
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50 views

Detrimental impact of magnetic field on PCB and battery?

We are developing a small consumer electronics product consisting of a small 4-layer PCB along with a few PDM microphones and BLE chip/ an antenna, as well as a LiPo battery. We are locating a small ...
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1answer
77 views

Replacing a magnetic speaker with a non-magnetic one

I need to mount a speaker next to a magnetic compass. Any suggestions? I have a becker radio which comes with a traditional 4 ohm moving coil magnetic speaker. Due to space limitations I don't really ...
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2answers
95 views

Does this coil topology work at high frequencies?

I have a cast iron wok and an induction hob. My understanding is that a ~24kHz AC in the hob's coil causes heating in the wok due to eddy currents from the varying magnetic field. Sadly, the iron ...
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4answers
4k views

Why does magnet wire need to be insulated?

What is it about having multiple coils that enables the magnetic field? Why can't I just have one big wire or threaded wire on a motor? Sorry, it's kind of a baby question but I couldn't find the ...
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2answers
68 views

How do I convert the units of a moving magnetic field to volts?

Copper wire wrapped around an iron core produces current when a strong magnet is moved in its vicinity. I gather the "magnet movement" part is expressed in units of "weber" (kg⋅m2⋅s−2⋅A−1) or perhaps ...
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30 views

Magnetic Field Strength Measurement at Extreme Temperatures

Hi I have just been given a project at work and we are magnetically stress testing DUTs at extreme temperatures going from -40 Degrees Celsius to 200 Degrees Celsius, I need to come up with a way that ...
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1answer
63 views

Questions on Inductor Selection guide from TI [closed]

I have been researching on Selecting inductors for Buck Application and came across an Application report from TI. I have few questions which are listed below: On ...
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2answers
68 views

A contradiction regarding flux conservation

Consider a simple circuit Initially switch S was opened till steady state is reached and then it was closed. My understanding regarding inductors is that you can't have a SUDDEN change in current ...
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1answer
56 views

Ethernet magnetics [duplicate]

I am working on a system prototype which includes two ethernet switches (KSZ9896) to provide Ethernet Gigabit connectivity between several devices (let's call them slaves, from now on); every slave ...
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2answers
88 views

“Electromagnet 5kg DC 3V 5V 6V 12V” - what do these multiple voltages mean?

I wanna buy an electromagnet from aliexpress and many of them are lifter magnets and have 6V, 12V, 24V and 5kg. So if i choose the 6V option does that mean the magnet can lift 5kg at 6V? Why would ...
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1answer
32 views

Does waveform shape affect transformer eddy current loss as frequency changes but peak voltage is fixed?

I'm trying to figure out how eddy currents change with frequency. While learning about this its occurred to me that eddy currents might be impacted differently as frequency changes, if the voltage is ...
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1answer
108 views

What impact does winding tightly versus loosely have on transformer performance?

To make it simple (and actually, directly relevant to what I am working on): what impact does winding tightness have on transformer performance? Lets assume typical laminated EI / EE 60hz transformer, ...
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1answer
31 views

Measuring a magnetic pulse using a coil, and circuit adjustments

I have the following circuit, I am using it to create a pulsed magnetic field, in the coil. I am trying to measure and verify the magnetic field in the coil. I am testing it with 40 V to drive the ...
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2answers
54 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 ...
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2answers
363 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 ...
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1answer
74 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 ...
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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 ...
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1answer
88 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 ...
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2answers
120 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 ...
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2answers
42 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 ...
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1answer
123 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 ...
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3answers
244 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 ...
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1answer
113 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 ...
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0answers
141 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 ...
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0answers
52 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 ...
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2answers
136 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 ...
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2answers
74 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 ...
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0answers
170 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 ...
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2answers
44 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? ...
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1answer
70 views

Toroid coating got scratched

Will there be any performance effect if the torroid coating gets scratched?
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1answer
382 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 ...
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0answers
51 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 ...
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0answers
52 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 ...
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3answers
48 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 ?
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2answers
559 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 ...
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1answer
51 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 ...
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1answer
34 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 ...
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2answers
63 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 ...
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3answers
122 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 ...
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1answer
65 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. ...
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3answers
176 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 ...
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2answers
467 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 ...
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0answers
56 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 ...
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1answer
138 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.
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0answers
213 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 ...
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0answers
61 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 ...
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2answers
175 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....