Questions tagged [magnetics]
Important to inductors, transformers, generators, motors, magnetic fields, inductive heating, magnetic storage, permanent magnets
4
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2answers
80 views
Why is the the permeability of a ferromagnetic material given as B/H not it's slope dB/dH?
I was going through my Electromagentics book by Sadiku where it was mentioned as a point that permeability of ferromagnetic material is given by the ratio of B(magnetic flux density) to H(magnetic ...
-1
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0answers
48 views
Magnetic lens supplier [on hold]
What companies sell magnetic lenses?
Google searching yielded no results for magnetic lens suppliers.
My application is pricing out a TEM.
3
votes
1answer
49 views
Should Ethernet MDI Pairs all be Length Matched (Inter-Pair) before going into magnetics?
I've been trying to find information for the above question and I can't seem to find anything. I have 1000 BASE-T lines coming from an Ethernet cable to a PCB mounted connector. I'm pretty much ...
1
vote
0answers
39 views
Are magnetically tunable surface acoustic wave devices commercially produced?
I have been reading up on studies of magnetically tunable surface acoustic wave devices, in general they note the relative velocity change or in some cases a frequency shift if it is part of an ...
2
votes
1answer
23 views
GbE Phy(88E1543) with POE+ PSE(LTC4266) design (POE+ magnetics? RJ45 with Integrated magnetics?)
I'm trying to understand how i can inject power to a 4 bank RJ45. I want to use these parts :
- LTC 4266 4 ports PSE (802.3 at compliant for GbE, in type1 class3 for 13W at each port)
- Marvell ...
1
vote
3answers
115 views
How can an induction motor be “self starting”
I read that all you need to start an induction motor is to apply the AC voltage, and with time the slippage decreases. How does this happen magnetically?
If a rotor, connected to a moderate sized ...
0
votes
1answer
28 views
Field geometry of external magnetic core?
If there is a coil with an external core, would the polarization of the magnetic field inside it be the opposite of an internal core?
For example, in the image:
If DC current were applied to the ...
3
votes
1answer
63 views
At what frequency is a transformers rated impedance measured
Where transformers have a specific impedance rating for the the primary/secondary, what frequency is this measured at?
For example, this transformer is rated at 40MHz - 860MHz with an impedance of 50/...
0
votes
2answers
67 views
Wireless Electricity Transmission model not working. Why?
I made wireless electricity transmission model using the principle of magnetic inductive coupling to transfer electricity between two separate coils. The model is very simple, known to everyone and ...
1
vote
2answers
75 views
Electrical model of a transformer
I would like to know what is the inductance (circled in red) of this part of this model? Is the value infinite? And only the inductance (circled in blue) is the value of the inductance of the ...
0
votes
0answers
48 views
Tuning antennas
I am working in a biomedical implant. I have to design an antenna for the wireless power transmission. The frequency that I am using is 13.56 MHz. I used some antennas found in some articles but when ...
1
vote
0answers
80 views
Can an inductor lose its characteristics permanently after short saturation?
I was testing a SMPS (boost) where I had an overcurrent due to overload for a few seconds.
The inductor saturation current is 2A.
Although I could not measure the current, I am quite sure that the ...
0
votes
0answers
38 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 ...
0
votes
0answers
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 ...
1
vote
1answer
37 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. ...
3
votes
0answers
56 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 ...
1
vote
1answer
80 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 ...
2
votes
2answers
96 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 ...
16
votes
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 ...
0
votes
2answers
71 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 ...
1
vote
0answers
31 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 ...
1
vote
1answer
65 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 ...
0
votes
2answers
69 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 ...
0
votes
1answer
60 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 ...
2
votes
2answers
102 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 ...
0
votes
1answer
35 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 ...
3
votes
1answer
127 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, ...
0
votes
1answer
36 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 ...
0
votes
2answers
70 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 ...
1
vote
2answers
551 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
81 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
votes
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
122 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
123 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
45 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
124 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
votes
3answers
266 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
vote
1answer
129 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
vote
2answers
178 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 ...
1
vote
0answers
53 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
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 ...
1
vote
2answers
78 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
votes
0answers
184 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
45 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
votes
1answer
72 views
Toroid coating got scratched
Will there be any performance effect if the torroid coating gets scratched?
3
votes
1answer
492 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
71 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
59 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
votes
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 ?
0
votes
2answers
710 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 ...
