Questions tagged [magnetic-flux]
The sum normal component of a magnetic field passing through a surface.
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Why are induction motor cores laminated to prevent eddy currents?
The permeable iron alloy cores of induction motor rotors are formed from thin laminated sheets, designed to prevent eddy current flow and thus "reduce losses", but isn't the whole point of ...
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Does operating an iron core near its saturation field reduce performance?
I am sizing an iron core for an electromagnet, and I am uncertain if there are disadvantages to operating close to the saturation flux density. If the saturation field is X, would it be better (more ...
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Why we use constant value of magnetic flux in transformers
I have a confusion regarding the formulas of the transformer. I have seen in many places people using a constant value of the flux B in the transformer equation:
turns per volt=1/(1.44 x Bmax x A x f)...
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How Far Should Mu Metal Be From An Inductor to Leave Its Internal Behavior Unchanged?
I have an air core inductor.
Since its magnetic field will be large, and it will turn on and off rapidly, I assume it will make a lot of noise.
I don't want that noise to disturb the PCB's nearby, so ...
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Use nickel as a flux ring
I'm designing an outrunner for a specific application. Rather than use steel to hold the magnets in the flux ring, can pure nickel be used? Nickel is a magnetic material, but has decent oxidation ...
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How do I find a formula for the reluctance of an E core with three coils?
In order to make progress with a problem, I need to find the reluctance of an E-core with a coil around each 'branch' of the E-core. I have the gap, the number of coils, and the dimensions of the core,...
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Calculate motor flux of a PMSM
I am struggling with the calculation of the motor flux for a RPX22-042V24 PMSM. I know back EMF, Torque constant and several other values from the datasheet. But I found different ways to calculate ...
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Want someone to review my Helmholtz coil design to see if I am missing something obvious before I fabricate it?
I am planning to construct a Helmholtz coil and wanted electrical engineers to take a look just so I know I am not overlooking anything.
The max field strength I am looking for is 200 Gauss. I ran ...
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What role does permanent magnet strength play in BLDC/PMSM performance?
It seems to me like stronger permanent magnets are preferred by motor designers, but my current understanding of what role they play in performance is fuzzy at best. I would assume that stronger ...
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Selection of the utilization factor for the calculation of the transformer for the DAB converter
DAB Converter:
When calculating the parameters of a transformer, it is necessary to know the utilization factor of the transformer (Ku).
Here it is 0.3.
The utilization factor of the transformer ...
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flux density value in a transformer
I am working on making a simple step-down transformer whose input will be 220V and output will be 12 V. The formula I have seen for calculating the turns per volt being calculated by the following ...
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Understanding voltage in simple electromagnet and DC motors
I made a simple electromagnet with enameled copper wire wrapped many times around a metal allen wrench. I attached the electromagnet to my PSU and it works great, but I do not understand the voltage ...
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How can the magnetic field produced by the shading ring of a solenoid valve be 90° out of phase compared to the coil magnetic field?
I am trying to understand how the shading ring in solenoid valves is able to produce a 90° out phase magnetic field compared to the coil's magnetic field. The logic seems different from a shaded pole ...
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Parallel magnetic circuit with 2 air gaps
I have the following ferromagnetic core.
N = 300
core thickness = 5 cm
relative permeability = 2000
the air gap's efective area rises 5%.
1 A going through the coil
I need to know the flux going ...
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EMF Sensors - Tri-axial Inductors vs Tri-axial Magnetometers
I took apart a bunch of EMF sensors (such as this one) and found that almost all of them instead of having a magnetometer inside, have usually three inductors. In the case I just shared, it has 3 33mH ...
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Equation relating alternating magnetic field strength to induced voltage in search coil
I have a search coil (loop area A, N turns) placed normal to an alternating magnetic field with equation B(t)=Bp.sin(2.pi.f.t), B=field strength at time t, Bp=peak field strength, f=frequency, t=time. ...
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What is the flux linkage or inductance or induced voltage per unit length of the hollow tube conductor surrounding the inner conductor?
What is the flux linkage or inductance or induced voltage per unit length of the hollow tube conductor surrounding the inner conductor in some section due to the current in the inner thin conductor?
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How can a constant flux machine store varying amounts of energy in its magnetic field?
A transformer is said to be a constant (i.e., constant RMS) flux machine. If load currents increase, how can the transformer store more energy in its magnetic field if it cannot accomodate a higher ...
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Induced current on secondary winding in transformer reinduce current in primary winding?
I am trying to understand what happens when PCB lines are magnetically coupled and form transformers and affect currents or distort voltages that is carried over them. I know if primary side in ...
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About the I1N1 = I2N2 equation
I have a silly question about this equation which is very frequently used in ideal transformer relations. If I draw the electrical equivalent circuit of the core, then the MMFs of 2 coils N1I1 would ...
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Ideal transformers - why doesn't voltage drop for primary winding account for secondary current?
The first figure below from Power Systems Analysis (Grainger/Stevenson/Chang) shows an ideal transformer. The authors write v1 as shown. Later on in the same chapter, however, the authors write v1 as ...
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Is power dissipation constant for a given mass of copper generating a given magnetic field?
What I mean, is that for a given field and a given mass of copper coil, power dissipation is independent of the form of that copper, whether thick wires or thin.
Is it true?
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Does infinite magnetic permeability (e.g. for an ideal transformer) violate conservation of energy?
The ideal transformer is supposed to have infinite magnetic permeability.
Creating infinite magnetic field lines from a finite applied field sounds like... a violation of conservation of energy or ...
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Geometry of magnetic flux in EM induction
Image of surface, shown in blue, through which magnetic flux passes, indicating the boundary in red, in motion at velocity v:
In the Wikipedia article on Magnetic Flux, it is said that an EMF is ...
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What could be the reason behind the variation in coil size inside Apple's Magic Trackpad 2 haptic motor?
**Disclaimer: This is a speculative question looking for electromagnetic coil advice, using Apple construction decisions as the talking point.
Looking through iFixit's teardown of the Apple Magic ...
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Dowell 1-D Eddy Current Model
About this paper, I have a question; please see the yellow part.
I don't understand why the current density distribution in
the conductor is only related to the y-coordinate.
Can someone tell me in a ...
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Effect of phase current on magnetic flux density in synchronous machines
I am working on a project on synchronous machines and I am testing different phase current values and observing the magnetic flux density in different parts of the machine, such as teeth, stator yoke, ...
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What am I doing wrong with metal detector coil?
I saw on the internet a lot of people making metal detectors so I was thinking of building my own.
I took 35 turns of 0.5 mm wire over a 20 cm diameter air core, connected it to a function generator (-...
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Placing a reed switch behind a metal plate
If put a reed switch behind a metal plate in plastic casing and have the bar magnet sweep across the plate in parallel, would the reed switch activate? I would try it myself but the reed switches that ...
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Search coils in metal finders
I have been looking into some DIY metal detector projects and search coil designs and got confused:
Why do most coil designs use thicker wire for TX and thinner wire for RX?
Why do some coil designs ...
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DC saturation current of a power transformer of a given VA rating
Correct me please. As far as I know the magnetic flux density B is a function of current, core permeability and its geometry. So let's take a power transformer rated to S VA. So it can withstand \$I_{...
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Toroidal coil as current sensor
Is there a simple way to estimate the amount of flux that is caught by a toroid coil (filled by some core material, like powder iron for example), which surrounds a straight wire with a current ...
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How to calculate the maximum flux density or max inductance of a ferromagnetic material of cross sectional area A and length l?
I am doing an experiment where I am making a power transformer where I am keeping the cross sectional area of primary leg and secondary leg different. I don't want the primary leg to hold more than a ...
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How many winding turns in a HV power transformer?
I'm creating a simplified 2D model of 3 three-winding 132/22 kV, 40 MVA transformers that I'll use to calculate the magnetic field surrounding them.
Now, the turn ratio is of course 132/22, but is ...
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Will primary flux & secondary flux (back MMF) in a transformer attract or repel each other?
I couldn't find it on google or may be I am not using the right keywords, if my terminologies are not sounding accurate, please bear with me, I am beginner in electrical engineering.
When the primary ...
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Why does magnetic flux decrease as turns increase in a coil but opposite is the case in magnetic circuits?
In magnetic fields, we have $$N \times I = \phi \times R$$ where \$N\$ is the number of turns, \$I\$ is the current, \$\phi\$ is the flux, and \$R\$ is the magnetic reluctance.
But in coils, we have $$...
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Formula to calculate saturation parameters of a power transformer?
I have recently learnt to build power transformers, my requirement is to make primary core reach right below saturation. I researched on google and found that load current has nothing to do with the ...
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Can a weak external magnetic field damage a magnetron?
I have a 40-year old microwave oven. I temporarily attached a magnetic flashlight to the side of it. Its 5/8"-diameter magnet is likely a neodymium magnet, strong enough to secure the 10-ounce ...
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determining the Bmax for inductor design
at this moment of this youtube video following graph is presented for selecting the proper maximum flux density.
the considered proper amount of core loss is 100mW/cm^3. is this a general amount for ...
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Is this a "gapped" ferrite transformer/choke?
Here, two "E" cores are bonded together with brown epoxy. There isn't any intentional, visible gap, yet there are three bond points and that must introduce some gap...
How are these ...
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Does the direction of coil winding impact the direction of induced voltage?
I have taken and modified a bit the following image from a similar question, where it was explained that the direction of the coil winding does not impact the direction of the current: Does coil ...
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Tesla’s AC motor: questions on operation
The Tesla Patent for the AC motor claims a circular disk can be used in place of the rectangular piece of steel which rotates in the motor. The disc is more efficient. I can see how the rectangular ...
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How can one calculate at surface the electric or magnetic field strength for 50Hz 240VAC wire at 1 meter depth?
How can one approximately calculate at surface the electric or magnetic field strength for 50Hz 240VAC wire buried at 1 meter soil depth for a given current?
Say in sandy clay soil with no mineral ...
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Disconnected wire still lit Tester turns on
I have multiple wires going through an electrical PVC conduit.
Two phase wire carrying 220v AC of 1.5mm gauge.
Two neutral wire carrying of 1.5 mm gauge.
One wire for earthing (grounding) of 1 mm ...
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How does balancing currents within a cable or conduit cancel its magnetic fields?
I know the NEC requires all current carrying conductors of the same circuit to be included in the same cable or conduit [300.3(B)], but why? I think it is because the magnetic field generated by ...
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Does coil winding impact current direction? (Lenz Law)
When a magnet is moving toward a wire loop north-side first, the current goes counterclockwise according to the magnet's perspective, as shown in the image below from Wikipedia. Now, consider a ...
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Why can we say \$F=\phi R=NI=HL\$ according to \$V=IR\$?
Magnetomotive force is a quantity appearing in the equation for the magnetic flux in a magnetic circuit,this is the explanation of Magnetomotive force from WIKI : https://en.wikipedia.org/wiki/...
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Why is a DC motor's back EMF constant for a given RPM
I was trying to prove this mathematically from the definition of EMF being the change in magnetic flux over time.
Starting with
$$ \Phi=BAcos(\theta)$$
Then differentiate w.r.t time (assuming B field ...
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What happens to the permanent magnet flux of this synchronous motor?
Considering a synchronous motor with permanent magnets (1 pair)
If there is a synchronous motor with permanent magnets and I was given the initial permanent magnet flux
Y_mp = e0(at 15 rps) / w (at 15 ...
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Automatic metal detector using an Arduino
I did a project on automated metal detector, but I am not clear on the circuit.
I built the circuit connecting a resistor to pin A4 on the Arduino, and a diode capacitor setup in series too.
I don't ...
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