Questions tagged [magnetics]

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

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14 views

High speed switching electromagnet control circuit

I am not very familiar with high speed switching magnets, and need help finding a control circuit that has adjustable frequency and duration for High Rate Switching Electromagnets, with a digital ...
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23 views

Active short circuit of motor phases to prevent higher voltages, what actually happens here?

So we have been using this technique called 'Active Short Circuit(ASC)' whenever the battery is disconnected or the inverter is being run from external bodies. So what actually happens in the coil ...
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1answer
41 views

Increase emf received from a coil without changing flux source

I have a situation where I'm trying to increase the amount of power received by a coil. To my understanding, I can increase the emf (voltage) by doing one of 4 things: Increase the number of coils (\$...
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48 views

What defines the maximum primary current of a (sensor-only) current transformer?

Take the Coilcraft CS1200L for example, which states the sensed current maximum is 35 A. This limit doesn't seem to be defined by the wire size which can fit through the hole (5 mm) as you can pass > ...
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2answers
76 views

Stacking M.O.T. to create an E-E core

I just came across this site looking for answers on some questions I have concerning microwave oven transformers (M.O.T.). I am currently going into my third year as an E.E. student and I am trying to ...
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46 views

Question about Biot Savart Law using vectors

This is a Biot savart law question using vectors and I tried this question and I want to check my answer is correct or not. And please show me the correct answer if wrong. I uploaded my Answer. ...
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1answer
50 views

Sending flyback current to another inductor using crossed diodes

So, here is the context. We have two electromagnets (modeled as R1 and L1, and R2 and L2), their state is dictated by a microcontroller which sends PWM to Q1 and Q2. The signal sent to Q1 and Q2 is a ...
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2answers
94 views

Bob Smith termination for Ethernet magnetics

I know that Bob Smith termination is recommended for Ethernet differential pairs. Please refer the below image for Bob Smith termination resistor placement. As far as I know, Bob Smith terminations ...
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2answers
100 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 ...
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1answer
81 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 ...
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42 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 ...
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1answer
27 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 ...
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3answers
126 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 ...
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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 ...
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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/...
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2answers
83 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 ...
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2answers
85 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 ...
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53 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 ...
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81 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 ...
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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 ...
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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
40 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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59 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
90 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
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 ...
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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
73 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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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 ...
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1answer
74 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
74 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
68 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
120 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
37 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
152 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
45 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
86 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
792 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
88 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
176 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
135 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
48 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
128 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
298 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
157 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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1answer
237 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
54 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
141 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
80 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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200 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 ...