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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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2
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2answers
901 views

Danger of Saturation of Primary Coil in a Flyback

I was reading a book, "switching power supply design - Abraham Pressman", specifically the section about flyback converters. One part I'm not quite sure I understand is where he says that the ...
0
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1answer
62 views

Externally toggle relay

Is it possible to force a relay to toggle without changing the input to the coil? i.e. if the relay (a sealed SPDT, say) has 0V on the coil such that NC is connected, it is theoretically possible that ...
1
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1answer
3k views

Will plastic influence a magnetic field?

First of all sorry for my English. If, for example I will "create" magnet by passing current through a coil. And than I will "wrap" this piece with plastic or some other material, will the "magnet ...
14
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12answers
4k views

Tracking rotation with extremely high accuracy

I would like to track the angular position of a fairly slow motorized rotating arm (direct-drive; see illustration below) -- but require angular accuracy of under 0.05°, and similar resolution. As @...
1
vote
1answer
950 views

neodymium magnet - how it affects a circuit

I am trying to develop a connector which can join both sides by a magnet. I got the idea of using a neodymium magnet , but I was thinking that if this could in one way or another affect circuit ...
0
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0answers
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 ...
1
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0answers
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 ...
2
votes
1answer
457 views

Why don't Inductors have voltage ratings, but transformers do?

Inductors don't have voltage rating, but transformers do... why is that? Why not just put a current, frequency, and turns ratio for transformers and be done?
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2answers
632 views

How is the current induced in this circuit?

Rectangle FBCE is the conducting wire. The circle is where magnetic field exists.The perimeter of the circle is NOT a conducting wire. R1,R2,...are different resistances. If the magnetic field(B) is ...
2
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3answers
153 views

why cannot use permanent magnets for large electricity production

Why cannot use permanent magnets for large electricity generation as they donot require power to produce strong magnneticfield
0
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1answer
63 views

Opposing EMF's with an odd change…?

A conductor in case 1 has two separate uniform magnetic fields \$B_1\$ & \$B_2\$: The magnetic fields(the blue rectangles are the field regions parallel to the conductor, while X's are the ...
2
votes
1answer
2k views

Hall effect sensor operational distance from magnet

I want to use a this hall effect sensor to detect the presence of magnet. I'm pretty sure I understand how to use the hall effect sensor, but I'm not sure how to calculate the distance the sensor can ...
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0answers
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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1answer
129 views

DC MMF and flux density variation in space

If flux density produced by DC current is sinusoidally distributed in space why do we say that DC MMF is space invariant?
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1answer
101 views

Long Term effects of saturating isolation txfr

I have a 1:1 isolation transformer that's rated for 25VA. I'm consuming 30VA, 20W. I've noticed because I'm saturating it, the txfr is no longer 1:1, it's more like 1:1.1. Other than this issue, for ...
12
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5answers
3k views

Can a transformer work if the core is not circular?

I am trying to build a transformer to convert 12V AC power to 5V AC. Here is what I have right now: I haven't adjusted the coil ratio yet but I tried it just to see if there would be any output and ...
-1
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3answers
199 views

Magnetic Field vs E-M Field

I have got some questions on this topic based on the best answers I get to these: -1- If magnetic fields arise due to electric currents in conductors, we say they are not E-M waves in nature; it is ...
0
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1answer
64 views

magnetic flux cut by a magnet

I have two magnets A and B: Magnet A is movable, Magnet B is fixed. Magnet A is smaller and weaker (surface area of 1 Square cm) , where as magnet B is stronger and bigger (surface area of 4 Square ...
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2answers
1k views

Clamp Meter Working Principle

Basic theory of clamp meter to measure rms of current wave. What I have in mind is that wire creates the changing flux that induces voltage in the meter.This voltage is calibrated ? Also how does the ...
1
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1answer
793 views

Bricked IMU using a magnet?

I think I may have bricked my IMU or seriously damaged it earlier this week. I have the Adafruit 9-DOF IMU Breakout - L3GD20H + LSM303 (link: http://www.adafruit.com/products/1714) which has an ...
1
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1answer
159 views

Where can I find correct documentation of old floppy drive formats?

I have an old drum machine with an ancient proprietary 3.5" SONY floppy disk drive with no information on the device itself that I have seen. The performance is spotty and it's very picky about disks. ...
0
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2answers
29 views

Potential lose of time-dependent currents in presence of static magnetic fields

A time-dependent current (either DC or AC) that creates a changing magnetic field around the wire, in absence of other materials, only lose current in heat proportional to ohmic resistance of wire ...
2
votes
2answers
295 views

Can a planar transformer replace a laminated transformer for 50Hz AC conversion?

I have seen planar magnetics transformers even with isolation up to 20 kV. However those devices seem to be designed for DC/DC conversion in 100 kHz range. I am wondering whether low frequency ...
1
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1answer
558 views

Hall-sensor replacement for reed switch

I have a device in which a reed switch is encased in potting compound. (So impossible to identify.) My problem is, that for my application the switch is too slow. I am considering replacing it with a ...
1
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1answer
146 views

questions on shielding static magnetic field

It seems that using ferromagnetic materials is the easiest way to shield static magnetic field. But is it still working in strong field strength(up to 5T)? Another question is that are mu-metal (iron-...
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2answers
1k views

Flux in transformers

I have found it very difficult to find what actually happens with primary and secondary generated flux in transformers, I understand the normal transformer theory but it doesn't add up in reality! I ...
1
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1answer
4k views

How do electric and magnetic fields affect electronic circuits?

I have come across those requirements: "The equipment shall not be susceptible to DC magnetic fields of up to 60 μT." "The equipment shall not be susceptible to electric fields of up to 140dBuV/m ...
2
votes
1answer
2k views

POE external Magnetics Alternative to magnetic RJ45 jack ieee803af

I can't use a magnetic jack for this POE PD (ieee803af), because we use another connector (M12). Looking for components to replace the internal magnetics, I found that almost all components and ...
0
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1answer
274 views

Inductor Core Loss: Volt-uS vs. Irms vs. Switcher Frequency

For DC to DC application, I see these charts often for inductors, but I don't understand what they actually mean. What does this chart mean, and how does it relate Volt-uS, Irms, & Freq? Edit: ...
5
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4answers
2k views

How does a transformer transmit power from the primary to the secondary?

I'm trying to get my head wrapped around transformer operation and in the process regretting the times I snoozed in my Electromagnetics class as a EE student back when I was a lad :) I'm looking for ...
1
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2answers
9k views

Why is HV kept open in OC test of transformer?

Why is HV kept open in OC test of transformer? Also, why is LV shorted in SC test of the transformer? (Generally this is preferred - why?)
2
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1answer
299 views

Create a vest to detect contact

I want to make a laser hunt type game with my son using Nerf Guns. I can modify the Nerf bullet to put some sort of device on the top of the bullet (obviously something not too heavy). It would be ...
1
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1answer
160 views

Magnetic contact circuit

Which is the best circuit for using a magnetic contact for turning on a LED strip? I would like to turn on a strip led with 12V 7A battery, but: 1 - if I use only the magnetic contact it will be ...
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2answers
197 views

Extend an rj45 Jack

I want to extend the Ethernet port (of my raspberry pi) using a short bit of cable plugges in into the Ethernet Port and solider to another rj45-jack. In the jack I have here, are some built-in coils ...
0
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1answer
391 views

Which is the best material to create a magnetic field?

I'm trying to create a magnetic field and I'm also trying to induct electricity wirelessly to a light bulb. What I have to do is create a round coil but I'm not sure what is the most conductive ...
1
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1answer
134 views

3 axis magnetometer issue in one axis

I have several 3-axis magnetometers mounted on breadboards, and they all read correctly in the x and z directions. The Y direction is very strange; when turned to read ...
-1
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1answer
108 views

Motor without magnetism [duplicate]

Every electric motor I know, takes electricity and converts it over a magnetic field, for generating movement. Is it possible to generate significant movement, based only only on electrons movement?
12
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3answers
822 views

Electrical Machines based on Electric Fields

Our teacher asked us this question during the lecture for Power Electromagnetics. We know that Electric Fields and Magnetic Fields are easily transformable into one another. And they are used greatly ...
2
votes
2answers
323 views

How build coil for respiratory magnetometer or find a better option (hall effect)?

I am trying to build an respiratory magnetometer. This device is no longer widely used even thought it was well liked. The reason it is no longer used is due to the fact that the coils used in it were ...
1
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1answer
73 views

How to determine the minimum proximity of magnet to an AC line for no electrical impedance?

As the title says, I am wanting to calculate the minimum proximity for a magnet to be near a AC line for no electrical impedance. My scenario is this: I have a theoretical device like MagSafe (Apple'...
0
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1answer
166 views

Mitigate the effects of magnetic induction heating in a three phase AC system

To mitigate the effects of magnetic induction heating in a three phase AC system, it is common practice to group the conductors and to keep them in the same raceway. Also, three phase power is ...
2
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2answers
3k views

Magnetic equivalent circuit with permanent magnets

I am fighting to understand how permanent magnets are inserted in magnetic equivalent circuits. In the image below is an example, at the left, the physical representation of an Iron core with a ...
0
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1answer
90 views

Bit persistence on a Hard Disk Drive

I was wondering if there was a time limit to the "persistence" of bits on a hard drive, a classical SATA for example. If I'm correct, bits are written by a magnetizing head in some cells on the hard ...
0
votes
1answer
167 views

Magnetic flux outside a solenoid perpendicular to the direction of axis of solenoid

I know that using straight forward Biot-Svart law it is possible to calculate field inside a solenoid or at a point on an axis away from the circular coil. Now is it possible to calculate the Flux ...
4
votes
1answer
859 views

Maximizing force of magnetic mass accelerator

I am planning to build a coil gun to fire small neodymium magnets out of a pipe. For this I am planning to use a large 400 Farad 2.7 Volt capacitor. I am wondering how many coils of wire I should ...
4
votes
2answers
202 views

Thickness of low frequency Mu shield calculation

I am dealing with a low frequency varying magnetic field, say 10 - 100Hz with a magnitude of 0.8T. It seems shielding at this frequency gets tricky. Even though Mu is capable of doing it, there should ...
1
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1answer
250 views

Would proximity to water affect a magnetometer

I'm using an InvenSense MPU9150 as a tilt-compensated compass in an autonomous sailboat. I'm trying to decide where to put the the control board, with options being in a dry box on top of the "deck," ...
1
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1answer
460 views

Can I increase inductance using permanent magnet ?

I know that when I insert a ferromagnetic core inside an air-cored coil, the inductance increases. What if I inserted a permanent magnet with a cylindrical shape into an air-cored coil, does the ...
2
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1answer
2k views

Why is the Litz Wire twisted?

I understand that dividing a wire into multiple insulated pieces reduce the Eddy Currents, and that reduces the magnetic field inside the wire, which leads to increased skin depth. But why do they ...
0
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2answers
263 views

Super fast magnetic field by an electromagnet?

Was wondering about the possibility of creating a magnetic field in milliseconds or less? I know it's possible based on certain labs achieving 60-100 Tesla and more. But what about creating a 2 - 5 ...