# Questions tagged [magnetic-flux]

The sum normal component of a magnetic field passing through a surface.

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848 views

### Assigning a notion of voltage even when there is a changing magnetic field

In Walter Lewin's lecture, he finds depending on how you keep the lead of the voltmeter for a circuit in a changing magnetic field, you will measure different values]. This experiment is discussed ...
121 views

### Taking into consideration the information provided, would the motor output the intended power?

Well, I'm not an electrical engineer and I'm trying to design a direct drive axial flux brushless torque motor with 300 kW with little weight as possible. I'm never going to actually build it because ...
653 views

### From a flux point of view, how can we explain that the equivalent inductance is half when identical inductors are connected in parallel?

The equivalent inductance of 2 identical inductance connected in parallel ( ignoring mutual coupling) is half of the orginal . This result is usually derived from the argument of identical voltage ...
1 vote
128 views

### Magnetising Inductance / Primary Inductance

I provided a picture below which shows the transformer calculations and LTspice simulation. In the 1'st picture L11 = 100.5 µH. This value is the inductance of primary side of the transformer. In the ...
142 views

### Mean Free Path of Magnetic Core

I don't understand how they got the mean free paths (ls) of each leg. I know that I should be calculating the longest + the shortest paths and divide them by two, but I don't know HOW I should be ...
65 views

### Question when obtaining magnetic flux density B

I am trying to obtain the magnetic flux density B of a toroidal transformer with one winding around the core. I am injecting a voltage in the terminals of the winding, and I am measuring this voltage ...
1 vote
1k views

### Why does my in-wheel BLDC motor have sinusoidal back emf (line to line) when rotated by external system?

I have an in-wheel BLDC motor with 46 poles (permanent magnet) on the rotor and 51 slots in the stator. When I used an external machine to rotate my in-wheel BLDC motor, then measuring across two ...
1 vote
89 views

### Core Loss of a Transformer

According to the Prof. Sam Ben-Yaakov, he uses the Core loss - $P_v$ ($kW/m^3$) versus Flux Density - B (mT) graph which is provided by the core manufacturers datasheet to select the ΔB. The ...
1 vote
79 views

### Modelling power transfer under saturation for 1:N current transformer in LTspice

A toroidal current transformer consisting of two half-toroids with air gaps, is clamped around an overhead 50 Hz AC power line carrying 50-300 A (i.e. a 1:N CT). It is used for energy harvesting. Is ...
86 views

### Transformer modelling / coupled inductors

I provided a picture which shows the transformer model and related equations. [Transformer Model and Equations] Source: https://www.youtube.com/watch?v=VrIfvNVBSyE I have 2 questions which are as ...
1 vote
93 views

### Calculation of transformer inductance value

I am trying to find a way to calculate the primary and secondary inductance of transformer. I learned that it is changing from one topology to another. My topology is Phase-Shifted Full-Bridge ...
1 vote
160 views

### 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 ...
1 vote
193 views

### Lenz Law and Magnetic fields in an Inductor

Hoping somebody can set me straight on the magnetic fields involved in an inductor when the current is changing. This is how I see it: The source current has a magnetic field. This changing flux ...
1 vote
615 views

### Why does the V/Hz ratio of a motor affect the magnetic field strength?

When the frequency is increased whilst keeping the voltage constant, the magnetic field strength is going to weaken... I don't understand why and what actually happens that causes the field strength ...
263 views

### Does hysteresis still occur if saturation is not achieved in a core?

When looking at a BH curve, what happens if the H field is raised to some level below saturation. For example we apply an H field that is only half way to saturation. On a BH plot this will trace a ...
1k views

### Can a slanted magnetic field be created with this insulated stranded wire arrangement?

I am considering building a small-scale experimental coil gun because I have an idea of how a magnetized projectile could be rotated while it is traveling through the coil(s), similar to how a bullet ...
35 views

### Can the formula for magnetic field intensity be used for cores with varying cross sectional area?

Can the formula H = NI/l be used for cores with varying cross sectional areas?
204 views

### High magnetic permeability material at 100MHz

I'm doing experiments as a hobby and was trying to find a material with good (very good) magnetic permeability at least at 100 MHz (higher frequencies are even better). Ideally the material would have ...
28 views

### Equivalent inductance seen from a winding

I would be having a little trouble understanding how to do this problem of magnetic circuits. It asks me to calculate the equivalent inductance seen from winding N2. I know how to calculate the ...
99 views

### Magnetic Force Equation

Is there any equation where I can take a metal with a given volume/mass, with a certain amount of magnetic flux in it (in teslas) and find out how much force (in newtons) it exerts a given distance ...
35 views

### Magnetic lines geometry inside a dc motor

How are the magnetic lines of the armature and stator field distributed? Are they always perpendicular to each other or do they align in every half cycle (while the rotor is rotating)? I suppose that ...
153 views

### Example problem of induced emf in a 100 turn coil by a 100 turn coil which has 90kHz sin wave input voltage

Main Question: Let's say there are two coils each 100 turn and diameter 30 mm, And the second coil is perpendicular to the first coil's magnetic field (placed both coils next to each other; we can see ...
76 views

### Example problem of induced emf in a coil travelling with some velocity and perpendicular to the earth's magnetic field

I have a example problem which I created myself just out of curiosity, Question: Let's say a copper wire coil(20mm dimeter(r=10mm)) of 3 turns(N=3) is moving along the surface(Note-coil is not ...
49 views

### If I have two magnets repelling each other, will they always form a peak in the middle?

If I have two identical magnets, aligned so they repel each other a distance of X apart and at a height of Z I have Hall effect sensor, the peak of the magnetic field sensed will be at the distance X/...
42 views

### Magnetic field generated by a current-carrying wire

When dealing with the magnetic field generated by a current-carrying wire, the formula for the magnetic flux density is B = μi/2π·d, but what if the point is located on the wire it self? In this case ...
37 views

### Identifying and designing coils for generating parallel magnetic fields with smooth gradients

What is this coil called (see image) (blue line is field, blue circle is clockwise oriented coil, red circle is counter-clockwise oriented coil), and are there any tools that help design it? ...
2k views

### Why are Halbach Arrays useful in PM motors?

I understand how Halbach arrays strengthen the magnetic field on one side of the array. I also know that, in a permanent magnet (PM) motor, there is already a limit on the air gap flux you can design ...
766 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. ...
1 vote
614 views

### 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 Wikipedia. Its equation is: F=...
61 views

### What is the consideration when installing or replacing the shaft of an induction motor?

Here are two picture of my washing machine's motor. I am not sure whether you still have such that machine in your country. It is a top loading washing machine's washing motor (a another smaller one ...
113 views

### Direction of magnetic flux in magnetic circuit

In the first picture attached,we see a ring shaped magnetic circuit with two magnetomotive forces. Now,in the solution to this problem,it was said that the two sources generate flux in the same ...
81 views

### Would a electromagnet be used to detect the presence of a permanent magnet?

I was wondering if there is any way I could use an electromagnet to detect the presence of a permanent magnet. I am specifically thinking of using a planar type small coil. Maybe use a core or ...
1 vote
161 views

### How do steel laminations reduce eddy current losses in a transformer?

All online materials I have read so far state that laminations reduce eddy currents but how is this so? I mean why would currents be smaller this way than having a big block of unlaminated iron core ...
330 views

### How to measure flux in transformer in LTspice?

I wish to check the flux through a transformer core in my LTspice simulation. I have set up a push-pull converter simulation using a transformer with a turns ratio of 1 : 1.1, a supply voltage of 12 V ...
127 views

### Problem acquiring B-H curve

I'm trying to acquire the BH curve of a toroidal current transformer in saturation, having the primary and secondary current. The formulas I am using are: B = (1/NsS) Integral(Vs(t)dt) H = (Ip*Np)/l \$...
1 vote
475 views

### Is ferrite core inductance similar to iron?

My 0.5" (1/2 inch) iron core inductor did not have a high inductance due to (I assume) eddy currents. Theory seems to suggest that ferrite cores are the ticket to increase inductance. I ordered ...
142 views

### Expression vectorial to magnetic field $\vec{H}$ in infinite semi-plane conductor

I have some difficult to figure out the second expression about the contribution of magnetic field as you see below: Problem: A wire conductor, infinite long (Z axis), conduct a current constant equal ...
73 views

### Magnetic interaction between resolver & motor windings?

Scenario: Synchronous electric motor whose rotor position is measured by a resolver. Won't the magnetic field created by the motor stator & rotor, link with the primary & secondary windings ...
79 views

### Does continuity equation applies for magnetic charge and magnetic current?

I wonder if, since we are capable of defining a charge and some magnetic currents, we can apply the continuity equation to them in such a way that: \frac{\partial \rho_{\text{mag}}}{\...
1 vote
211 views

### How is the holding force of this electromagnet so large?

I am designing a system that uses the magnetic force to fix an object in its place. I plan to connect an I-core to my object and fix it to a fixed C-core by letting a magnetic flux flow through both ...
1k views

### 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 ...
89 views

### PMSM Motor Permanent Magnet Flux Linkage

I want to know the Permanent Magnet Flux Linkage of my PMSM motor. I need that to implement a Speed control for my motor. Without this value I cannot do the necessary calculations to make the motor ...
451 views

### 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 ...
1k views

### 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 ...
142 views

### 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 ...
666 views

### 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 ...
1 vote
65 views

### 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 ...
1k views

### 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)...
1 vote