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Questions tagged [magnetics]

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

46 questions with no upvoted or accepted answers
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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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1answer
72 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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217 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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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 ...
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41 views

What to do with unused Ethernet magnetic center taps on POE?

I'm using a MAGJACK GIG PDJACK 1X1 CLASS 4 (Molex # 0857914020 - Link: https://www.digikey.com/products/en?keywords=WM9656-ND) to run POE on a 100MBit network connection. I thought this was a nice ...
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49 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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0answers
43 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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82 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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1answer
49 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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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
298 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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70 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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61 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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40 views

Any deleterious effect from very strong, close magnets on NiMH cells over time?

This question probably isn't a perfect fit for this SE, but I did find this question: Will placing a strong magnet near my electric skateboard Li-Ion Battery pack damage or discharge it? This is a ...
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1answer
119 views

Short range wireless pulse transmission in wind anemometer

I have an old windmil-type anemometer, something like this: (Illustrative image, the real unit is 40+ year old soviet-made device with presumably no operational active components inside) My project ...
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94 views

Why are chokes nonlinear around 0A ? What inductors do not exhibit this behaviour?

I want to demonstrate that I can control the current in the winding of my single phase motor (a limited angle torquer) with a bandwidth greater than 3kHz. The phase resistance of the motor is 20Ohm, ...
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184 views

FSPL formula for near magnetic field?

I would like to know the precise formula for the Free Space Path Loss in case of a Magnetic Field in the Near Field region. We all know the popular FSPL formula, but this is only for the far field, ...
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1answer
831 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 ...
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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 ...
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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 ...
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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 ...
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71 views

Is there a way to shield the fluidics of a solenoid valve from its magnetic field?

Are there any solenoid valves on the market that specifically shield the fluidics from the magnetic field of the solenoid actuation? Either by physically redirecting the fluidics around the coils or ...
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1k views

Building an electromagnet to work over an air gap

I am currently working on a project where I am building an electromagnet that works over an air gap. Specifically a gap of about 0.3 inches. The electromagnet type was selected because I need to be ...
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169 views

Ground plane and magnets

I am making a wheel encoder out of a Hall Effect sensor with magnets in a concentric circle on the wheel. The Hall effect sensor is on a 2-layer 9x5mm pcb. I usually fill in the layers by drawing a ...
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1answer
30 views

Magnetometer moving along a line with different measurement?

I am testing on a magnetometer and found that moving the magnetometer along a straight line within the range around 1m, and the measurement varies. From what I understand, moving magnetometer along a ...
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39 views

How do I determine what magnet to use at a specific distance for a reed switch?

I have a reed switch that shows a 10AT to 15AT operate range on the data sheet. I need to determine if specific magnets will fire the switch, and at what distance. The magnets I'm looking at though, ...
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1answer
32 views

Is it possible to influence the working behaviour of a simple dc motor with an outside electromagnet?

I am using a simple DC-Motor 9V like this one. Now, I am curious about what influence an outside magnet / magnetic field would have on the working behavior of this motor? I would like to use the ...
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28 views

HR911105A or similar integrated magnetics for POE

Is it ok to use this RJ-45 socket for low power POE application (just to power the uC)? The only available datasheet : https://www.google.com/url?sa=t&source=web&rct=j&url=http://www....
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36 views

Magnetic Linear Positioning with no magnetic disturbances at all

I recently saw a machine where it used a hall sensor or a magnetometer for linear positioning (the sensor is wrapped in some opaque protection so I don't know what it actually is which is the real ...
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21 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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56 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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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

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
40 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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311 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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69 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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57 views

Can I create a uniform magnetic field with an n52 magnet?

I want to build a ribbon speaker and I've read that one of the greatest sources of distortion in these types of speakers is the non uniform magnetic field along the length of the magnet. I've also ...
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1answer
62 views

Net-Zero Magnetic Fields in a Three-Phase Motor

When a three phase motor in running and you clamp an amp-meter around all three of the phase wires, you should expect to read zero because the magnetic fields cancel each other out. I'm having ...
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1answer
65 views

acquiring conductivity through curl of magnetic field density and Ampere's circuital law

I have some question. I want to acquire conductivity and I used Ampere's circuital law. The problem is A solid conductor of circular cross section with a radius of 5mm has a conductivity that ...
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1answer
387 views

Appropriate models to model magnetic components in LTspice and what are the pros and cons?

I'm looking for appropriate models to model magnetic components, mostly transformers and perhaps for chokes as well, for use in LTspice. I've heard briefly of some models, like Jiles-Atherton-model (...
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210 views

unstable magnetometer readings

I did the magnetic calibration here on the LSM303DLHC for a field roughly 48 uT. The method seems to have worked in that the combined bias (b) values went from ...
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1answer
77 views

Why isn't solid permalloy used for common mode chokes?

When reverse engineering a common mode choke from a line filter I found a wrap of very thin metallic foil inside the plastic housing of the toroid core. A little research on magnetic materials ...
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315 views

Ferrite core characterization

I need to make a dc dc converter and have some ferrite toroids but I don't have the datasheet of the cores so I need to know how much energy are capable do store the core and what current can they ...
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1answer
71 views

Can cellphone magnetic holders affect the CPU?

My concern is mostly related to the various IC components such as CPU. I know that one of the problems of miniaturization is that electons jump to neighbouring lanes. Given how tight things are in an ...