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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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5
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1answer
843 views

Winding method of a toroid core

I find some text about the winding of a toroid core as below: But what's the math and physics behind these? BTW: Can someone suggest some good books about the design of an inductor/transformer not ...
2
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2answers
524 views

Turns for saturating a toroid at a particular frequency

I need to know the winding turns required to saturate a toroid for a particular drive frequency. The toroid I have is having the following dimensions OD = 19 mm Thickness = 8 mm Effective Area (Ae) =...
0
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1answer
186 views

Double magnetics for ethernet?

I have a main board with a 10/100 MAC and PHY. This board also includes a discrete magnetics. The board is connected via a suitable high speed board-to-board connector to another board, that contains ...
10
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2answers
2k views

Very small transformer powering a microwave oven

I have recently cannibalized a 6 year old microwave oven. I was very surprised to find the following beast at the electrical entry of the oven: The reason: this small 1:1 isolation transformer was ...
0
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1answer
84 views

saturation level of Kool Mu material

I have a toroidal core which has effective area of .656 cm^2 from magnetics , in magnetics page they say it has 10,500 gauss saturation level (about 1 tesla!). so.. when designing a flyback "...
1
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1answer
832 views

Modeling A Current Transformer in FEMM

I would like to accurately design and model a current transformer in FEMM. I'm hoping this will enable me to accurately estimate the secondary current in a current transformer, including it's phase ...
2
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2answers
1k views

Are ferrite beads supposed to be magnetic?

I have replaced the ferrite bead on my audio cable with new ones that I just bought. But I have tested them and they aren't magnetic, it's just like a cylindric metal inside it, but I thought it has ...
1
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3answers
2k views

Good layout for Ethernet magnetics

I'm laying out a PCB with 100Mbps Ethernet (SMSC LAN8710 Phy), a Pulse 1102FNL magnetics transformer plus the RJ45 [a MagJack isn't an option]. The transformer - probably as with most? - is 16 pin, ...
0
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2answers
535 views

Current from Hall effect sensor

We are working on a project. Our goal is to measure the DC current of a cable ranging to 1A-50A. However the hall meter doesn't seem to react at all when putting a cable with 2A close to it. We get a ...
0
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1answer
4k views

Calculating the mean path length of a core

I have the following magnetic circuit problem: For the left hand core, the mean path length calculated in the solution manual is 1.11m. However what I don't understand is, why is the length of the ...
0
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1answer
521 views

Ethernet PoE Magnetics Pin swap

I have the following circuit right now Is it possible to connect PHY_TRXP0 on TD1- and PHY_TRXN0 on TD1+ and taking ETH_MX1_P from MX1- and ETH_MX1_N on MX1+ respectively? Signals on RJ45 will go as ...
3
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1answer
161 views

Approaching an ideal inductor

It is common to see capacitors in parallel, with smaller and smaller capacitance, in order to reduce the parasitic ESR (and the equivalent series inductance). This allows obtaining relatively big ...
0
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1answer
124 views

Wireless power transmission system

Would introducing a magnetic amplifier to a wireless power transmission system made of two lc circuits increase efficiency? Would the diode system shown on the website also increase efficiency?
0
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3answers
183 views

Shouldnt the magnetic field at a certain angle be minimum in center of current loop?

Magnetic field is strongest at the center of current loop. But if it is calculated along a single magnetic field line like this: A and B are magnetic lines. Shouldnt it minimum in the center since ...
3
votes
2answers
460 views

why is the outside of an electromagnet not magnetic?

On the electromagnet (5 Volts DC, built upon a transformer core) setup pictured below , only the core part is magnetic (when powered, it attracts a piece of steel) but not the 2 "wings" outside that ...
9
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1answer
2k views

Ethernet: distance from PHY to magnetics

I am confused as to the preferred placement of Ethernet PHY and magnetics. I thought that in general, the closer the better. But then SMSC/Microchip app note (http://ww1.microchip.com/downloads/en/...
0
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4answers
2k views

Should I use a permanent magnet inside a solenoid for an electromagnet shuttle?

I'd like to make some kind of actuator/vibrator but much stronger. I thought of using a static, tubular solenoid, driven with AC current. Inside it would be a mobile permanent magnet cylinder (...
9
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2answers
3k views

How can this layout be improved? (Gigabit Ethernet with discrete magnetics and POE)

Answer: No there is nothing majorly wrong with the layout, it turns out that the ethernet transformer was out of spec by 0.2dB on Insertion loss, when paired with the PHY IC we are using. Question ...
1
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0answers
74 views

Is it possible to redesign a magnetron to be a receiving device?

Magnetron- As a transmitter A magentron is used to produce microwaves, by oscillating a magnetic field, and an electric field at a specific frequency. Magnetron- As a receiver Is it possible to ...
5
votes
4answers
2k views

How is the degaussing feature in the HMC5883L 3-Axis Digital Compass chip correctly used?

edit/tl;dr: The set/reset strap driver is an H-bridge circuit to deliver 10 mA of DC current to a strap which temporarily produces about a 1.1 gauss magnetic field offset. A change in the measurement ...
1
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1answer
73 views

Electromagnetic coupling structure of a generator?

I was referring to this paper (pg. 7) for designing my own small-scale permanent magnet generator. I came across this electromagnetic coupling structure of the proposed APMM: I am not able to ...
1
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3answers
99 views

Is it possible to use a coil to create sustained displacement/preasure? without a permanent magnet?

So, as far as I understand, speakers are basically coils coupled with permanent magnets, then when a current is run through the coil it creates a magnetic field, pushing out against the permanent ...
1
vote
1answer
101 views

How ignition coil in automobile works..?? what are the winding count for ignition coil..?

I just want to make ignition coil on my own. can you please help to done primary and secondary winding for same..? 40KV output required from 12v input supply.
0
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1answer
214 views

Trying to understand the working principle of a weird transformer driver / oscillator

I'm trying to fix the high-voltage power supply of an old scope. The HV transformer is burnt, and I'm trying to replace it with a similar one (EPC19 core), but I'm failing. I already know how to wind ...
0
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2answers
235 views

why are pm (permanent magnet) machines synchronous? and how do I start them?

Let's consider just one pole pair. I know from reading my book that a pm machine will have the angular speed of its rotor equal to the speed of the rotating magnet field that the three phase winding ...
0
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1answer
69 views

Transformer secondary wired to primary and secondary of second transformer

simulate this circuit – Schematic created using CircuitLab I see something like this for ethernet, and it confuses me. What is it for? What does it do? Could I remove that from the schematic?
2
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1answer
885 views

Influence of a magnetic field on coil impedance

If you take a coil and make a current flow through it, the coil creates a magnetic field. This field induces a voltage into the coil that produces a counter current that weakens the primary current ...
1
vote
1answer
358 views

How does inductance change with presence of different directional magnetic fields?

If I design a coil driver for a certain application, I assume there is a fixed load right? It may have drive any inductance between an interval but you can not drive any coil, because the driver is ...
0
votes
1answer
290 views

Ferromagnetic core with air gap

N=200 I=N*8A l=20cm=2*10^-1 d(delta)=1mm=10^-3 M=? M=(B/μ)-H How can I get the vector of magnetization? The relative permeability is not known. Everything I ...
0
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1answer
532 views

electromagnet repelling permanent magnet [closed]

I have an electromagnet (turned off) with an iron core in front of a permanent magnet. At this stage they attract each other. Will any current do if I want them to repel each other, or is there a ...
2
votes
3answers
1k views

low frequency 1-10Hz transformer

I have a 20V, 2 Amp Max, 10Hz sine wave generator, I would like to be able to connect a transformer to step up and down the voltage. How would I go about finding a transformer that I could connect to ...
-2
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1answer
46 views

In electromagnetic inductance, which one is more efficient, to focus all power to move one part or split it to move both at the same time?

Assuming equal force is used, which one would be more efficient when it comes to generating current through electromagnetic induction: to use 100% of available force to move the permanent magnet only ...
4
votes
2answers
4k views

How to properly wind a high frequency / high voltage transformer?

Please, is there any practical tip / caveat I should be aware, when winding a high-frequency transformer? I'm used to wind 50/60Hz transformers and they do work ok, but now I'm trying to make a high ...
0
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1answer
852 views

Magnets in Transformers Design

What is the advantages, and disadvantages of using neodymium magnets instead of ferrite cores in transformers? How would the magnetic flux density vary of such a transformer utilizing a neodymium ...
1
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0answers
156 views

Why compass module is affected by its x,y position, if my phone's compass work in the same environment?

I am using hmc5883L on an autonomus robot. It shall remain in a 1 meter squared area. I have recently discovered that its reading changes up to 20 degrees on different positions even when it is facing ...
0
votes
1answer
2k views

using a magnet to trigger a traffic light

Here is the link to the Traffic Detector Handbook from the Federal Highway Administration: http://www.fhwa.dot.gov/publications/research/operations/its/06108/02.cfm This will explain more about ...
0
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1answer
72 views

Effects on the exterior magnetic field from a field induced by a wire?

I have an experimental set-up where I place a conductive wire in a magnetic field created by an electromagnet like so: There is current flowing in a wire as well(aside from the electromagnet) ...
6
votes
1answer
261 views

Where are Ćuk converters

According to "the art of electronics" (p 651) and other internet sources, the ćuk switch converter has the most desirable properties: continuous input and output current waveforms, boosting and ...
1
vote
1answer
990 views

Reed switch sensitivity

I've built a setup where I've placed a reed switch near the water meter in my house. Every 0.5 litre the switch gets triggered and my Raspberry Pi does the rest of the work. My gas meter also outputs ...
2
votes
0answers
106 views

Closed loop shapes with zero mutual inductance?

I have done numerous searches trying to find any mention of theory or experimentation done on determining closed current loop shapes that have zero mutual inductance and...no dice! Of course you can ...
0
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1answer
46 views

Magnetically shielding an actuator

We need to magnetically shield a solenoid that activates this valve (shown below) Just slipping a mild steel cap over the end does not do the job, nor appears to have any screening effect at all. Any ...
1
vote
1answer
2k views

How to increase an electromagnet's magnetic field size?

I made this electromagnet out of a microwave oven transformer by taking out the secondary coil. It very strong but it can only attract the metals if I bring it really close. How do increase the ...
0
votes
2answers
507 views

Ways to use electromagnets to pick up metal shavings at a distance

I work at a rotor machining plant and there is an issue for shutting a line down to clean up metal shavings, causes too much down time. I was thinking of using a strong electromagnet to have a "pick ...
0
votes
1answer
287 views

Formula for electromagnet strength parallel, outside the coil

I am working on a electromagnet project to collect metal shavings off the floor after machining. I have a formula for the magnetic strength at a distance from the ends, but not parallel to the coil. ...
0
votes
1answer
512 views

Magnetic switch with no moving parts

Is there a magnetic switch (like a reed switch) but with no moving parts? I need a switch that can be turned on by a magnetic field but won't move around due to tremendous shock absorption.
2
votes
3answers
529 views

Core loss appearing in buck converter ripple current

I have been told (and have also seen experimentally) that an inductor with a high core loss will introduce "glitches" to the ripple current in a switch mode power supply. I have tried researching this,...
2
votes
4answers
1k views

Hall effect device for circa 1 tesla gaussmeter

I'm thinking about building an unsophisticated bench instrument for measuring magnetic field density, just to support my learning about electromagnetism and building magnetics for power electronics ...
1
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4answers
237 views

Suggestions for moldable ferromagnetic material?

I'm trying to build a sort of three-axis stepper motor that consists of a sphere with a permanent bar magnet embedded in it surrounded by a cube (slightly smaller than the sphere, so that the sides of ...
14
votes
5answers
3k views

Why are reed switches made in glass tubes?

Why are reed switches made in glass tubes? Reed switches sense magnetic fields, and glass is not the only material not affected by a magnetic field. They can use plastic for example. Why are most of ...
1
vote
3answers
153 views

Magnetic modulation/ induction

I've been looking for a viable means of communication under water (other than sonars), be it short or mid-ranged, and I have come across MM and MI. I am no engineer, so I need help with this, and I ...