Winding a coil for maximum magnetic field

[mrvneng1992]

Hello frineds!
I am looking for one approach that design my own multilayer coil with mild steel core.
this desired coil have one core that made from mild steel and i want to design this coil for maximum magnetic field intensity(B) so that the core didn't be saturated!
please guide me as you can and i am be appreciate for that!

 

[gophert]

Hello frineds!
I am looking for one approach that design my own multilayer coil with mild steel core.
this desired coil have one core that made from mild steel and i want to design this coil for maximum magnetic field intensity(B) so that the core didn't be saturated!
please guide me as you can and i am be appreciate for that!

What frequency? Mild steel laminates, solid steel?, core size? What is your target current, or target field strength? What s the goal of this device - a choke, a magnet, a transformer, ...?

I can't help you if you don't help yourself.

 

[MrAl]

Heres the universal transformer calc, you can work out b flux density by thinking the solenoid as a transformer primary.
You can still use this for dc but you'll need to fiddle the frequency part, for that you'll need to have an idea on the sol's inductance.

Hi,

I would just add dimensions.
'a' is area in square centimeters in that formula ... very important.

 

[MrAl]

Hello frineds!
I am looking for one approach that design my own multilayer coil with mild steel core.
this desired coil have one core that made from mild steel and i want to design this coil for maximum magnetic field intensity(B) so that the core didn't be saturated!
please guide me as you can and i am be appreciate for that!

Hi,

When you say steel core, is there a closed magnetic path or some gap?

 

[dr pepper]

I understand you want a mild steel core, and if your constrained to that fair enough.
Silicon steel however would be a lot better and is used in commercial transformers.

 

[mrvneng1992]

What frequency? Mild steel laminates, solid steel?, core size? What is your target current, or target field strength? What s the goal of this device - a choke, a magnet, a transformer, ...?

I can't help you if you don't help yourself.

hi dear gophert!
I give DC current to my coil and i have solid steel core!
The core size will determine after design of my coil geometry! (some resources said that the length of coil and core must be equal to have maximum velocity!)
my target is design a optimum coil for Electromagnetic launcher! that have maximum magnetic field strength to accelerate the steel core, but i don't want to saturate the steel core because in this state no more force will e added on core! so i have think that may be i can find one approach that constrain the magnetic field strength to prevent this phenomena!
thank you for the time you left to answer my question.

 

[mrvneng1992]

Hi,

When you say steel core, is there a closed magnetic path or some gap?

I just have a coil that one core inside it
its just like a linear electric machine!

 

[mrvneng1992]

I understand you want a mild steel core, and if your constrained to that fair enough.
Silicon steel however would be a lot better and is used in commercial transformers.

can you compare the permeability of these two?

 

[rjenkinsgb]

my target is design a optimum coil for Electromagnetic launcher

An electromagnetic launcher - a coil gun - does not usually use a single coil, it uses a sequence of coils to accelerate the object along the barrel.

Although a single coil can be use, it's far less effective and harder to build as the coil pulls the object to it's centre, it does not "throw" it - you have to create a strong field and then also demagnetise it again, before the projectile passes the centre, otherwise you slow the projectile down before it leaves the coil.

A multi-stage (or multi-phase) one can vary the field in stages along the barrel so the projectile is always being accelerated.

Note that also with some types of multi-phase coilgun the projectile does not need to be iron - the gun is effectively a "linear induction motor" and a copper or aluminium slug (or coil) will work as well or better than iron as that is lower resistance and can have a higher current induced in to it, creating its own magnetic field that reacts to the drive coils.
Think of it as a bit like a "squirrel cage" AC motor with the outer stator unwrapped and flattened out, then the aluminium and copper rotor flattened out to run along it.

Have a look through this article for some of the basic principles:
https://en.wikipedia.org/wiki/Coilgun

 

[MrAl]

I just have a coil that one core inside it
its just like a linear electric machine!

Hi,

Ok that's a little different than a transformer then because it's not a closed magnetic path.
The maximum energy is transferred when the impedance of the power source matches that of the coil. However, what the builders of these things usually do is discharge a bunch of capacitors into the load (the coil) to get a big kick. So it would be best for you to look up designs on the web that are already done and go from there.

 

[mrvneng1992]

An electromagnetic launcher - a coil gun - does not usually use a single coil, it uses a sequence of coils to accelerate the object along the barrel.

Although a single coil can be use, it's far less effective and harder to build as the coil pulls the object to it's centre, it does not "throw" it - you have to create a strong field and then also demagnetise it again, before the projectile passes the centre, otherwise you slow the projectile down before it leaves the coil.

A multi-stage (or multi-phase) one can vary the field in stages along the barrel so the projectile is always being accelerated.

Note that also with some types of multi-phase coilgun the projectile does not need to be iron - the gun is effectively a "linear induction motor" and a copper or aluminium slug (or coil) will work as well or better than iron as that is lower resistance and can have a higher current induced in to it, creating its own magnetic field that reacts to the drive coils.
Think of it as a bit like a "squirrel cage" AC motor with the outer stator unwrapped and flattened out, then the aluminium and copper rotor flattened out to run along it.

Have a look through this article for some of the basic principles:
https://en.wikipedia.org/wiki/Coilgun

yes i accept all of that you said and i knew all of those, but:
1- I want to design and make a reluctance accelerator NOT induction accelerator
2- I decided to gather information on how to principled design a coilgun.I have some information about the serie RLC circuit of coilgun.but at first i want to design a coil and more define a capacitor bank according to the coil that i made it because if that coil have low resistance, then the huge current from capacitor bank will damage to my switch (SCR or IGBT or MOSFET)!
3- soo in this step i want to design a best and optimum multi layer coil that have maximum magnetic field strength so that the core wouldn't be saturate as well as i have coil with suitable inductance and resistance
thanks

 

[mrvneng1992]

Hi,

Ok that's a little different than a transformer then because it's not a closed magnetic path.
The maximum energy is transferred when the impedance of the power source matches that of the coil. However, what the builders of these things usually do is discharge a bunch of capacitors into the load (the coil) to get a big kick. So it would be best for you to look up designs on the web that are already done and go from there.

Yes a knew that and i keep searching about that but any of resources don't discuss about the details . how to design a suitable coil for instance!

 

[rjenkinsgb]

Well, there is no "core" other than your projectile.

Magnetic field strength is simply ampere-turns, but with an application like yours the inductance is also critical as higher inductance (more turns) slows down the current rise.

That's why very high voltages are often used, to give a faster current increase.


I think the only way is to experiment. Start with a suitable plastic or fibreglass tube for the barrel then wind a test coil with rather more turns and thinner wire than you think are likely to be needed, to see how that interacts with your capacitor bank and switch device.
Those are a critical part of the system and the coil specs will very much depend on them.

Watch the waveform when you trigger it and see how fast the current rise is, compared to the length of the coil and the desired projectile velocity.
Try it both with and without the projectile, as the inductance will be higher with something acting as a core.
You could also try different iron & steel types at that stage to see what works best.

If the current rise and levels are not adequate, use thicker wire and fewer turns for the next test.
Half the turns would give a quarter the inductance so four times faster rise and higher peak current.


Until you have something to use as a basic for further estimations, it is pure and total guesswork.

 

[DerStrom8]

I'm afraid due to safety and liability concerns, coil guns are a forbidden topic here. Therefore this thread must be closed. Please understand the reason behind this closure and that it is nothing personal. Feel free to browse the rest of the forums.

Thank you,
Matt