# Questions tagged [magnetics]

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

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84 views

### How is slope compensation implemented in the UC3843?

I was reading about slope compensation in the datasheet of UC3843 and I have watched this tutorial on youtube which gave me a general idea and overview about what slope compensation is. Now regarding ...
2k views

### What does limit transferable power through a transformer?

Assume that there is a transformer as in the image above. The applied primary side voltage $E_1$ is always AC. We design the transformer so that the magnetizing flux $\Phi_m$ does not saturate the ...
55 views

### Ethernet coupler implementation on PCB - whether to use magnetics (transformer) or not?

I need to implement a sort of coupler on a PCB which has other things running, but without any connection to an Ethernet circuit (see drawing). One end of this 'coupler' connects (using a suitably ...
666 views

### Is magnetic flux in a transformer proportional to voltage or current?

Consider a transformer. I put a constant sine wave AC voltage through the primary circuit and a resistor on the secondary circuit. I know that the secondary voltage is proportional to change in ...
79 views

### Estimation of open-circuit inductance from the leakage inductance

The title may not reflect the problem I explained below. Please feel free to update. For a power supply application, I designed a transformer with a primary turns of 15 and a secondary turns of 4+4 (...
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 ...
2k views

### How accurate is my phone's magnetometer?

I'm trying to build a linear motor, for which purpose I bought this large permanent magnet. The website claims it has up to "13,500 Gauss", which is 1.35 tesla. However when I put my phone ...
2k views

### How to compare a magnetic loop antenna to a conventional antenna

I want to build a compact 1 MHz receive coil (antenna for very near field). For that I need to make a choice on whether to build a simple RF coil only consisting of wire and capacitors or using a coil ...
103 views

### Is this PFC choke design correct?

I would really appreciate it if you could check this inductor design, if there are any mistakes, or if it can be improved. I'm designing a $50\,\mathrm{\mu H}$ PFC choke for a totem-pole bridgeless ...
1 vote
149 views

### Transformer Secondary Discontinuity

I am using a step up transformer and I am getting a weird discontinuity in the secondary output. Has anyone seen anything like this before? I cant figure out what might cause this. In a one test setup ...
108 views

### Magnetic field in a tape

This is a theoretical question. Let's guess we have an unknown magnetic tape cassette, no brand, no numbers or other signs. The question is: do tools exist, that are able to analyze the magnetic field ...
3k views

I have seen a lot of projects that use a tape head, but there is very less information about how to build one yourself. Is this possible? I know that basically it is a metal core, with a coil around ...
1 vote
65 views

### How does a Current Injection clamp work from a physics persepective?

Current injection clamps are normally described as a transformer with a single turn secondary, which is all fine and good, but the construction of a transformer is different from a current clamp. ...
49 views

### Can I deduce the saturation current of a transformer from the rated wattage and maximum frequency?

I have an SMPS transformer EE10, but am not sure about the saturation current it has, I tried doing some internet research, all what I can get is this so far : I am trying to deduce the saturation ...
1 vote
185 views

### How to create rotating magnetic field using four electromagnets

How would you create a rotating magnetic field using 4 big electromagnets located equal distance around the DUT. The magnets are configured in pairs of two (magnets opposite each other), controlled by ...
169 views

### Difficulties in tuning magnetic levitation system on Arduino and MATLAB?

So I am dealing with a project that revolves around magnetically levitating an object below an electromagnet. I created a transfer function of it after making a mathematical model of it, and got this ...
29 views

### Measurement bias of Hall sensors with moving permanent magnets

I want to measure the magnetic flux density produced by a moving permanent magnet. In my case, the magnet would move left and right alternatively at speed of 10 mm/s, with a constant vertical distance ...
108 views

### Energy stored in a saturating inductor

We all know that the energy stored in an ideal inductor is $E=\frac{1}{2}LI^2$. However, real inductors with a ferromagnetic core don't have constant inductance. Particularly, when a specific field ...
431 views

### Inductance after core saturation

Looking at the datasheets of some drum core inductors, at higher currents the inductance drops significantly due to ferrite core saturation. But it seems inductance asymptotically approaches a value ...
184 views

### Why are common mode chokes used in Ethernet magnetics

I’m trying to understand the reason the common mode choke is required in Ethernet magnetics. To understand, if we look at the schematic, with the common mode choke (horizontal coils) removed, we are ...
186 views

### Microwave Turntable Absorption

Do microwaves turntables absorb some microwave radiation when being used? I heard that they can act as a minimum load on the magnetron. If this is true, can I interchange microwave turntables? Edit: ...
1 vote
214 views

### How do you calculate the B field for core loss in Steinmetz equations?

How does one calculate the B field for core loss in Steinmetz equation? I have a single turn inductor in a magnetic material. Is the core material shape relevant? Wouldn't the B field be variable ...
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 ...
1 vote
212 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 ...
109 views

### Inductance Computed As Length in Historical Document

In "Formulas and Tables for the Calculation of Mutual and Self-inductance.", many equations compute the inductance of an arrangement as a length. For example, Equation 95, on p. 150, states,...
1 vote
4k views

### How to increase an electromagnet's magnetic field size?

I made this electromagnet out of a microwave oven transformer by taking out the secondary coil. It very strong but it can only attract the metals if I bring it really close. How do increase the ...
205 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 ...
1 vote
129 views

### What are sources of extra low frequency magnetic field in a car with IC engine? [closed]

ELF analyser (16 Hz - 2 kHz) shows a magnetic field around 300- 2000 nT (at some position exceeding that) in car when petrol or diesel engine work. When RPM increase from idle to 2500 RPM, magnetic ...
100 views

### Transformer losses due to eddy currents. Why these losses are compensated by the transformer?

Here is my understanding of a transformer. Let's assume that we have the following ideal circuit, in which a coil is wrapped around a core and there are no core losses⎯excuse my crude drawing.         ...
1 vote
700 views

### Why would running the coil cable straight for ~10 inches affect metal detector sensitivity?

Metal detecting enthusiast here. I have been reading various posts pertaining to sensitivity of metal detectors. It is has been suggested that instead of immediately wrapping the coil cable around ...
1 vote
2k 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 (...
98 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 ...
2k views

### How can single phase induction motor's direction be reversed?

My house has a ceiling fan which has 2 wires which are connected to a capacitor, and Iam able to control the velocity and direction. After looking about these motors on the web I found out its ...
57 views

### Magnetization of an Electric Guitar String

I'm trying to calculate the magnetic field generated by electric guitar strings of various gauges. The strings are made of some ferromagnetic material (pure steel or pure nickel). They are magnetized ...
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/...
71 views

1 vote
120 views

### Transformer design and calculations

I am trying to find correct way of determining the transformer parameters. I provided a simple schematic of a PSFB (phase-shifted full bridge) converter below. How do we determine thr primary ...
1 vote
107 views

### Core demagnetisation - What is the condition?

Consider forward converter topology. What is necessary for core to be successfully demagnetised? Does the magnetising current has to reach absolute zero amps, or even little negative is advantage? How ...
80 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 ...