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What is the purpose of perpendicular "smaller" magnets in between the main magnets in a rotor of a motor? had never seen this before. Do they help?

This is more or less just transferred from Wikipedia, however: As @HarrySvensson indicates, this is a Halbach array, apparently used to create a magnetic field that is stronger on one side than the ...
K H's user avatar
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8 votes

Why are the poles of the stator and rotor taken differently in the picture below?

Magnetic lines of flux follow a convention and that convention is that lines of flux (leaving the "core") flow from a north pole to a south pole (through the air): -
Andy aka's user avatar
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8 votes
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What happens if the secondary of an ordinary transformer is left open?

The ideal transformer equation is: \$\frac{V1}{V2} =\frac{I2}{I1}\$ That's fine but then you go on to consider a non-ideal transformer: - Suppose the secondary is open (that means I2=0): it will ...
Andy aka's user avatar
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8 votes
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Does coil winding impact current direction? (Lenz Law)

What would happen if the solenoid was wound the other way In the second picture, I've put your first picture winding (now in red) in series with the winding from the 2nd picture (black). There is no ...
Andy aka's user avatar
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8 votes
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Placing a reed switch behind a metal plate

A steel plate is going to block most of the magnetic field of the magnet. There is no chance that a reed switch will work with the supplied magnet through 3mm of steel, but heroic efforts may be able ...
Jasen  Слава Україні's user avatar
7 votes

How does the length of a transformer's core affect its properties?

Some aspects are equivalent, some are different. Let's assume they are the same cross sectional area, and you want to make a transformer, perhaps a power transformer, operating from a fixed mains ...
Neil_UK's user avatar
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7 votes

What exactly carries energy in a transformer from primary to secondary?

The net (total) flux remains constant. When you allow a current to flow in the secondary, it creates its own flux in the core that partially cancels the flux originally produced by the primary. More ...
Dave Tweed's user avatar
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6 votes
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Unregulated Push pull converter simulation (LTspice) and flux walking

You've got one MOSFET driven at about 60% and the other MOSFET driven about 40% duty cycle - that puts dc into your transformer and walks the flux. If anyone reads this focusses on the 2nd picture ...
Andy aka's user avatar
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6 votes

Can I use rectified AC current to heat an object inside a induction coil?

What you are really trying to do is add DC bias current so that the coil current never has a zero crossing. This is misguided. The losses in the coil are basically entirely resistive, and will be a ...
user57037's user avatar
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6 votes
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What impact does winding tightly versus loosely have on transformer performance?

See my answer here if you want the theory behind the words below: - Normally, the flux will tend to want to concentrate in the ferrite core because that will have, by far, the lower magnetic ...
Andy aka's user avatar
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6 votes
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From a flux point of view, how can we explain that the equivalent inductance is half when identical inductors are connected in parallel?

There are many different ways you can characterize inductance, including several different was that could be called 'flux-oriented', so this is hardly the only way to look at this, but it is my ...
metacollin's user avatar
6 votes
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How does balancing currents within a cable or conduit cancel its magnetic fields?

To start, currents are not the same as bar magnets (i.e. permanent magnetic dipoles). Consider a pair of conductors carrying equal-but-opposite conventional currents (red): By the right hand rule, we ...
nanofarad's user avatar
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6 votes
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DC saturation current of a power transformer of a given VA rating

So the peak current used to find \$B\$ is \$I=I_{RMS}\cdot \sqrt2\$. No, that is not the case. The load current passing into the transformer primary and exiting on the secondary has nothing to do ...
Andy aka's user avatar
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6 votes
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Why we use constant value of magnetic flux in transformers

Secondary load current \$\times\$ secondary turns is exactly cancelled by the load current flowing in the primary \$\times\$ primary turns hence, fluxes associated with the secondary load are ...
Andy aka's user avatar
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6 votes

Why we use constant value of magnetic flux in transformers

Think of the transformer theoretical model (without parasitic elements): simulate this circuit – Schematic created using CircuitLab The ideal transformer (IDEAL TX above) has infinite ...
Rohat Kılıç's user avatar
6 votes
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Can a slanted magnetic field be created with this insulated stranded wire arrangement?

One trick you can try to get the rifling you desire is to put "rotating" stages between the linear stages. Effectively, you would have a motor stator in between the linear stages (look up 3-...
MOSFET's user avatar
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5 votes
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X-ray back-projection for conversion to hard-field magnetic induction tomography?

It turns out that it is possible to image slices through a metallic object such as an Aluminium coke can, using hard field magnetic induction tomography (MIT) Back Projection in x-ray tomography and ...
Brendan Darrer's user avatar
5 votes
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Calculation of magnetic field saturation inside coil core

Apart from the fact that you are probably misusing the length dimension of the ferrite, you are also miscalculating flux density quite badly (See further below). The length dimension for a ferrite ...
Andy aka's user avatar
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5 votes

Power output of a transformer with many secondary coils, each coil of turn exactly equal to that of primary?

If all coils have the same number of turns, they will all (theoretically) have the same voltage - 100VAC in on any coil, and all others will output 100 VAC. The total current from all secondary coils ...
Peter Bennett's user avatar
5 votes

Why does the current in a transformer's primary coil change when a load is attached to the secondary coil?

A more basic physics explanation is simply that conservation of energy holds*, and you can only stuff so much energy into the magnetic field of a transformer. So if you're taking energy out of the ...
TimWescott's user avatar
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5 votes

Where to purchase the iron core for an electromagnet?

The 1018 core is working just fine, doubling the field is exactly what's expected. The problem is the remaining air-gap in the magnetic circuit. Using the steel core inside the solenoid has more or ...
Neil_UK's user avatar
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5 votes
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Magnetic flux density in a point

It looks to me like you are calculating flux density: - Picture from here. So, use superposition. Note also that the external diameters of A and B are irrelevant to solve this.
Andy aka's user avatar
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5 votes

Why does inductor core saturation depend on the temperature?

This is mostly a solid-state physics question, but, to boil this down to something that we can answer without going into finesse of core material physics: Magnetism happens when in a material, you can ...
Marcus Müller's user avatar
5 votes

DC saturation current of a power transformer of a given VA rating

Calculate it backwards instead. Say we have a transformer with Ae = 200 mm2, le = 240 mm, μr = 10k, and Bsat = 1.2 T. First, solve for turns: $$ N = \frac{ V_\textrm{rms} }{ 4.44 B_\textrm{sat} F A_e ...
Tim Williams's user avatar
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5 votes
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Does hysteresis still occur if saturation is not achieved in a core?

Yes: From: https://www.researchgate.net/figure/A-family-of-B-H-loops-of-grain-oriented-electrical-steel_fig1_264585820 Query (for reference, further reading): https://www.google.com/search?q=b-h+loop+...
Tim Williams's user avatar
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4 votes
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How do you calculate the VA of a toroidal transformer core?

The only relevant quantities are size of the toroid, the saturation field, the frequency, and permitted temperature of operation. Windings, permaeability, don't figure. The cross section of the iron,...
Neil_UK's user avatar
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4 votes

How does the length of a transformer's core affect its properties?

The length of the core is used for determining the magnetic field strength, H (measured in ampere turns per metre). The "per metre" part is the mean length (\$l_e\$) of the core shown below: - So, if ...
Andy aka's user avatar
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4 votes
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Would spacing the magnets in a DC motor farther away from the armature increase RPM of the motor?

Yes. Field Weakening as it is known, is a tried and tested method of increasing the speed of wound field motors over a relatively small range, from the days when electronics for speed control didn't ...
Neil_UK's user avatar
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