Winding a strong electromagnet

[SkyWatcher123]

Hi folks, Does anyone know if a coil, an aircore coil for example when pulsed does the voltage rise instantly within a coil to max or close to the inputted voltage while it takes more time for current to build based on inductance?

[Xaverius]

@ Honk:  more voltage would be needed to overcome high Inductance due to eddy currents.  These can be eliminated with steel laminations that are insulated from one another.

@ CapNHook:  both (c) and (d) are correct, although naturally you would desire higher permeabilty in order to use lower input power.

@ SkyHook: the voltage is maximum initiallly, then the current rises relatively slowly to the maximum value.

[Kator01]

Hi capthook,

it turns out a bit more complicated than just permeability and we have to study a bit more about some physical fact( this is also true for me ) I just received this info from an engineer in New Zealand who has constructed an Aspden/Adam-Motor which runs with some excess-energy but is not OU at this stage of development. He was refering to this website here for Aspen/Adam-patent on this motor:

http://www.angelfire.com/ak5/energy21/adamsmotor.htm

Move down to ELECTRICAL MOTOR-GENERATOR ( common patent by Mr. Aspden/Adams ).

Notice : this website is not related to the person I got the message from. He was refering to this website because  he wanted to show me the basis of his design ( Figure 6 and 7 )

But before you read this you should read in Aspeden´s website where the extra-power we all are looking for
is located and how to tap it. It is in the air-gap. And if you have higher permeabilty you will have stronger attraction-forces and need more EM-cancelling-power but you will have more power returned from the air-gap.
Permability can be controlled as it is no a constant along increasing values of  Ampere/windings ( see in the download-section here a document I place named "Permeability of pure iron" ). Have a look at the diagramm only.
Now Aspden talks in the Power from Magnetism of the operating-point below the knee of the B-H-Curve, which can be achieved by magentic-bias of the core-lamination.
May be you already know this topic. It is of utmost importance to fully understand this. Read it three times. I just
read it the second time and still have some problems especially if it comes to his calculations.

http://www.aspden.org/reports/Es1/esr1.htm

Regards

Kator01

[Honk]

@ Honk:  more voltage would be needed to overcome high Inductance due to eddy currents.
These can be eliminated with steel laminations that are insulated from one another.

Yes, higher voltage will accelerate any coil regardless of the inductance, just like higher
voltage will accelerate the charge of a capacitor, if there is no current limiting factor.
And the higher the inductance the higher the voltage, but eddy currents have very little
to do with this. The slugginess is always present in a high inductance coil/electromagnet
regardless of the core material. A core will only amplify flux and increase inductance.
Just use the link I provided. It will give you all the answers you need about coil pulsing.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2
You just need to enter the Inductance, Resistance, Applied voltage and Pulse time.
This will calculate the achieved Current level at the specified Pulse time, aka Amp-Turns.
It can't be any simpler than that.

[Honk]

Hi folks, Does anyone know if a coil, an aircore coil for example when pulsed does the voltage rise instantly within a coil to max or close to the inputted voltage while it takes more time for current to build based on inductance?

When pulsing a coil the voltage will rise instantly (just as fast as you can apply it) but the current build-up is slow.
The higher the inductance the slower the build-up time. This is regardless of core material.
A ferromagnetic core amplifies the flux from the windings. And this process also increases inductance.
Ferromagnetic core amplification is named by Permeability. The higher the Permeability the greater the flux amplification.
The trade-off is higher inductance that slows down response time. Slow response = slow current build-up.
There is a middle way where the number of turns, aka amp-turns vs response time is the best combination.
This is totaly dependent on your needs in your own specific project. You'll just have to calculate, wind and measure
the outcome a lot of times. And then use this calculator to see if the amp-turns vs response time will do it for you.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indtra.html#c2