Questions tagged [magnetics]

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

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I am wondering if magnets can be safely used to connect power from one to the other? [closed]

I am thinking of trying to create a extension cord that can be taken apart or separated as needed. And rejoined at any length of cord but connected only through magnetic connections. So I'm wondering ...
HEO's user avatar
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3 votes
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Why are induction motor cores laminated to prevent eddy currents?

The permeable iron alloy cores of induction motor rotors are formed from thin laminated sheets, designed to prevent eddy current flow and thus "reduce losses", but isn't the whole point of ...
PersonWithName's user avatar
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Any information on magnetic braking with copper?

I have an engineering project where I have to design and build a model of a drop tower from a theme park. The tower itself can be no taller than 40cm. I plan to use magnetic braking with copper to ...
18jbrana's user avatar
2 votes
2 answers
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Does operating an iron core near its saturation field reduce performance?

I am sizing an iron core for an electromagnet, and I am uncertain if there are disadvantages to operating close to the saturation flux density. If the saturation field is X, would it be better (more ...
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How Far Should Mu Metal Be From An Inductor to Leave Its Internal Behavior Unchanged?

I have an air core inductor. Since its magnetic field will be large, and it will turn on and off rapidly, I assume it will make a lot of noise. I don't want that noise to disturb the PCB's nearby, so ...
James Strieter's user avatar
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Magnetics part with and without auto-transformer

I have 2 magnetics part. One magnetics is this (Circuit A configuration magnetics) & the other magnetics is this When I use the Halo part, the ethernet link is not up. But when I just replace the ...
Freshman's user avatar
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Why do metal finders not use any sensors other than search coils?

I was wondering why metal finders do not use any other sensors to recieve the magnetic signal instead of search coils. I have been looking at MEMS sensors used as digital compasses, for example. As ...
Ron Vaisman's user avatar
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Is there any practical purpose of placing read only memory (ROM) chip near a hard drive?

Premise: a PCB file has ROM chips (I think they are masked ROMs?) placed beside standard 3.5" HDDs, which has lead me to a few questions. While the product is off, I understand that the magnets ...
CodingFryCook's user avatar
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Calculate motor flux of a PMSM

I am struggling with the calculation of the motor flux for a RPX22-042V24 PMSM. I know back EMF, Torque constant and several other values from the datasheet. But I found different ways to calculate ...
hanss's user avatar
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Want someone to review my Helmholtz coil design to see if I am missing something obvious before I fabricate it?

I am planning to construct a Helmholtz coil and wanted electrical engineers to take a look just so I know I am not overlooking anything. The max field strength I am looking for is 200 Gauss. I ran ...
assasinchop7's user avatar
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Useing a PoE RJ45 ICM Magnetics but not using it for PoE?

I plan on using the Bel G27-122T-015 (PoE ICM RJ45) but I don't need it for PoE. Can I just leave these pins unconnected? The ICM already has an internal Bob Smith termination.
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Metal detector coil wire gauge [duplicate]

Many designs of metal detector coils use different gauges of wire for the TX and RX coils - why is that? Does the wire thickness influence other parameters rather then just the resistance and current ...
ron vais's user avatar
4 votes
1 answer
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What role does permanent magnet strength play in BLDC/PMSM performance?

It seems to me like stronger permanent magnets are preferred by motor designers, but my current understanding of what role they play in performance is fuzzy at best. I would assume that stronger ...
TheDarkSaint's user avatar
2 votes
1 answer
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What types of inductor cores exhibit magnetization?

My understanding of magnetization in core memories is as follows: a bit is written to an inductor's core by magnetizing it, by applying a large current. Later, the bit is read by observing the effect ...
personal_cloud's user avatar
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What is the best material for 200Hz power inductor?

I am looking for inductor core material working at about 200Hz. The inductor current is DC only, close to triangle with 5A average. I read for such purpose the amorphous alloys have a good performance,...
Michal Podmanický's user avatar
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3 answers
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How to calculate the maximum number of turns possible on a ferrite core?

I am designing a coupled inductor for a boost converter by following the step-by-step procedure for inductor design in Chapter 14 of the Fundamentals of Power Electronics. My specs are the following: ...
Hector's user avatar
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I want to make use of an Allegro A1324LUA-T Hall sensor to sense a very small magnetic field change. Would it be possible?

I am looking into using an Allegro A1324LUA-T for sensing very small magnetic field changes. The data sheet shows that the sensor gives a 5mV/G change in voltage so I can sense a 0.1 Gauss change if I ...
assasinchop7's user avatar
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Broadcom BCM54194 PHY Magnetics

I am designing an application board using a third party Ethernet Switch module. I am unable to get the Switch module manufacturer support on the recommended magnetics to use. I can see that the ...
TCP7532's user avatar
1 vote
1 answer
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Ethernet external magnetics layout

I am laying out a 10/100Mbps Ethernet PCB with discrete magnetics. From the magnetics to the PHY chip I have a system ground plane on the adjacent layer for the return path. From the connector to the ...
HV16's user avatar
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How can the magnetic field produced by the shading ring of a solenoid valve be 90° out of phase compared to the coil magnetic field?

I am trying to understand how the shading ring in solenoid valves is able to produce a 90° out phase magnetic field compared to the coil's magnetic field. The logic seems different from a shaded pole ...
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I want to find out the magnetic field strength of neodymium N35 grade magnet

I am making a horizontal axis wind turbine. I have neodymium N35 magnets. I want to find out the magnetic field strength of one. Its dimensions are 50mm x 25mm x 12mm.
Smrutiranjan's user avatar
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How do I create an AC electromagnet for a particular type of field generator?

I’m trying to generate a special sort of field in a spherical spinning iron core using two orthogonally oriented coils. One single-layer coil of 18 AWG magnet wire is wrapped directly onto most of the ...
magnetwhisperer's user avatar
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3 answers
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Should I use a step-up or step-down transformer to generate a magnetic field for a copper coil?

I want to generate a magnetic field from a coil made of copper. Let's consider a simple circuit with a power source (12VAC), a transformer and a coil. simulate this circuit – Schematic created ...
Jérémy Talbot-Pâquet's user avatar
1 vote
1 answer
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Parallel magnetic circuit with 2 air gaps

I have the following ferromagnetic core. N = 300 core thickness = 5 cm relative permeability = 2000 the air gap's efective area rises 5%. 1 A going through the coil I need to know the flux going ...
Aleat's user avatar
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EMF Sensors - Tri-axial Inductors vs Tri-axial Magnetometers

I took apart a bunch of EMF sensors (such as this one) and found that almost all of them instead of having a magnetometer inside, have usually three inductors. In the case I just shared, it has 3 33mH ...
Tom Hayden's user avatar
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2 answers
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Equation relating alternating magnetic field strength to induced voltage in search coil

I have a search coil (loop area A, N turns) placed normal to an alternating magnetic field with equation B(t)=Bp.sin(2.pi.f.t), B=field strength at time t, Bp=peak field strength, f=frequency, t=time. ...
user201341's user avatar
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0 answers
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Stepper motor stepping sequence analysis

I'm currently trying to educate myself on the stepper motor. The figure below is what I am trying to analyze. First I wanted to analyze the step angle for full step operation and half step. Which I ...
kam 's user avatar
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In an AC or DC motor, what force is causing the armature to rotate?

I read that when charge flows through a wire there is no north or south. So I assume the armature has no north or south, so depending on which direction charge is flowing through the armature windings ...
Sedumjoy's user avatar
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Why do we still need to calculate the equivalent exciting current \$I_{eq}\$ when we have the exciting current \$I_F\$ already?

Here is the compound DC machine schematic: The equivalent exciting current is \$I_{eq}=I_F+\frac{N_{SE}}{N_{SH}}I_A-\frac{F_{AR}}{N_{SH}}\$ \$F_{AR}\$: the equivalent magnetomotive force of armature-...
user16266657's user avatar
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Ethernet RJ45 Mg Jacks - CMC placement

Ethernet RJ45 Mg Jacks. Some have common mode chokes on the PHY side and some have chokes on the cable side. What's the difference? Some examples: https://www.sparkfun.com/datasheets/Prototyping/...
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1 answer
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Will a nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) impulse blind our signal response sensor?

After we send an impulse to the coil, when we start read the coil will have self oscillations. What influence will the self oscillations have on the read response? How can we deal with the self ...
Viacheslav Popika's user avatar
2 votes
0 answers
145 views

Flyback transformer design process review

I was hoping I could get some verification on my flyback design process, and some questions answered. The document I was following is from Fairchild, AN4137, and the steps below essentially outline ...
RogerDodger's user avatar
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1 answer
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Can magnetic levitation kits be stacked?

Hall-effect magnetic levitation kits are available (cheaply) and require manual assembly. You put electromagnets in the center and you have some board which controls the stability via a Hall sensor. ...
estinamir's user avatar
2 votes
1 answer
154 views

Does the orientation of the Ethernet magnetics matter?

I've this Ethernet magnetics transformer connected between the PHY and the Connector? Does the orientation of the magnetics with respect to the PHY matter? Meaning, should the common mode choke inside ...
user avatar
1 vote
2 answers
96 views

How to create rotating magnetic field using four electromagnets

How would you create a rotating magnetic field using 4 big electromagnets located equal distance around the DUT. The magnets are configured in pairs of two (magnets opposite each other), controlled by ...
super7800's user avatar
2 votes
1 answer
115 views

Ethernet communication on the same board : do I need a transformer? [duplicate]

I need to communicate between a microcontroller that has an integrated MAC (Datasheet) and a microprocessor that has an integrated MAC and PHY (Datasheet). The pins of the MAC on the processor are ...
uz3il's user avatar
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5 votes
2 answers
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Sampled 100 Hz sinusoidal signal from Hall sensor shows 10 Hz sidelobes when sampled at 500 Hz

I am working on a project where I need to measure an oscillating magnetic field that oscillates at a frequency of 100 Hz. For this reason, I am using a Hall sensor. I programmed the Hall sensor to ...
Mantabit's user avatar
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0 votes
1 answer
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What could be the reason behind the variation in coil size inside Apple's Magic Trackpad 2 haptic motor?

**Disclaimer: This is a speculative question looking for electromagnetic coil advice, using Apple construction decisions as the talking point. Looking through iFixit's teardown of the Apple Magic ...
ezra_vdj's user avatar
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13 votes
4 answers
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Why does this metallic magnetic core have so little core losses up until 100s of kHz?

I have a small signal transformer with values as in the below schematic (the simulate button works well to see the AC response). The values are measured and the simulated AC response agrees sort of ...
tobalt's user avatar
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How do we calculate the cross section area and EMF in a solenoid?

Case 1: Consider an air core solenoid \$S_0\$ with inner diameter \$(d_{in0})\$ = 10 cm and the cross section area of the wire = 0.1 cm, outer dia \$(d_{out0})\$ = 10.1 cm. The number of turns in the ...
student0's user avatar
1 vote
2 answers
59 views

Dowell 1-D Eddy Current Model

About this paper, I have a question; please see the yellow part. I don't understand why the current density distribution in the conductor is only related to the y-coordinate. Can someone tell me in a ...
Magnetic778's user avatar
0 votes
1 answer
93 views

Human body communication, magnetic vs capacitive coupling

I am reading a paper by Park and Mercier called Magnetic Human Body Communication (2015). They are looking into human body communication techniques and compare magnetic human body communication (mHBC) ...
Mart's user avatar
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3 votes
3 answers
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Intuition about inductor/transformer core shape nomenclature and performance impact

Due to some future projects, I feel I have to get more accustomed to winding my own transformers/inductors, so I have been reading about ferrite cores lately. One thing I can't really develop a ...
tobalt's user avatar
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-2 votes
1 answer
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Electronic Chess Board [closed]

I want to make a chess board that can detect where all of the pieces are and send this information to a computer (Chess.com). I looked into it, and it seems that the best way to do this would be with ...
Set's user avatar
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0 votes
1 answer
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Transformer MMF distribution

The below figure is referring to The Analysis and Comparison of Leakage Inductance in Different Winding Arrangements for Planar Transformer. It is a common method to use MMF distribution to estimate ...
Magnetic778's user avatar
3 votes
1 answer
237 views

Why am I getting Torque although stator and rotor fields are aligned?

I am working on a synchronous machine simulation project using FEMM. I am trying to find the rotor position that produces 0 torque. According to my understanding, this happens when both the rotor and ...
Zelreedy's user avatar
-1 votes
1 answer
38 views

What is the initial phase of the rotating magnetic field of a 2-pole stator?

How can one determine the starting phase of the rotating magnetic field? What I mean is, Are you able to determine the direction of the magnetic field, when knowing the values of the 3-phase stator ...
Zelreedy's user avatar
0 votes
2 answers
196 views

Can stronger consumer grade magnets affect solar cells?

Is there any evidence to suggest that stronger consumer grade magnets like the one in this magnetic phone holder can negatively impact the efficacy of consumer grade solar cells like the one in this ...
Byron Burdette's user avatar
4 votes
3 answers
686 views

If inductors opposes any change in electrical current, how can the magnetic field vary with time if the current is varying with time?

When I looked the definition of the inductors, I saw that: It opposes any change in electrical current. If the current is varying with time, the magnetic field is varying with time. So if 1. ...
XcellentEEE's user avatar
1 vote
2 answers
221 views

Full-Bridge DC-DC Converter Transformer

I try to design a full bridge DC-DC converter (hard switch) and I have some concerns about it's transformer design. As I know its transformer doesn't store energy and it doesn't have an air-gap? If ...
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