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Topic: Winding Some Coils (Read 1 time) previous topic - next topic

DROBNJAK

I guess it is a perenial question.

I need to wind some coils. Am I going to produce stronger magnetic field if I use lots of thinnest wire where many strands in the same section carry small current many times over. Or am I going to get a stronger magnetic field if I just use one single thick wire that can carry a huge amperage?

larryd

#1
May 21, 2017, 11:08 pm Last Edit: May 21, 2017, 11:09 pm by larryd
A car starter uses heavy gauge solid wire and lots of amps  ;)


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jackrae

The magnetic field strength is determined by the number of ampere-turns (A-T) on the coil.  How high an A-T count you can get on a particular former is a basic mathematical exercise based on wire diameter, wire stiffness and how neatly you can lay the layers of wire in.

You need to consider what voltage you have to drive the current and how much current at that voltage your supply can provide.

You need to consider what space you have available for the windings to occupy.

You need to consider if coil inductance is relevant; ie is the energising current AC or DC

Since coils are usually voltage driven devices, in general terms, lots of fine turns is usually better than a few thick ones, unless the coil is used as a current sensing device in which case the load current will determine required wire diameter, so requiring fewer turns and thicker wire.

krupski

#3
May 22, 2017, 01:12 am Last Edit: May 22, 2017, 01:12 am by krupski
I guess it is a perenial question.

I need to wind some coils. Am I going to produce stronger magnetic field if I use lots of thinnest wire where many strands in the same section carry small current many times over. Or am I going to get a stronger magnetic field if I just use one single thick wire that can carry a huge amperage?
In order for anyone to help you, we need to know what you want.

Are you building an electromagnet? A transformer? A choke? DC? AC? If AC, what frequency?

If electromagnet or transformer, what voltage?

There are LOTS of variables (wire resistance, wire gauge, current, volts-per-turn, core material depending on frequency and lots more).

Can't help you with zero information.

Gentlemen may prefer Blondes, but Real Men prefer Redheads!

MarkT

I guess it is a perenial question.

I need to wind some coils. Am I going to produce stronger magnetic field if I use lots of thinnest wire where many strands in the same section carry small current many times over. Or am I going to get a stronger magnetic field if I just use one single thick wire that can carry a huge amperage?
For the same amount of copper the magnetic field depends on the total current for the whole winding, not
whether its 10A and 1 turn or 1A with 10 turns or 0.1A and 100 turns...  For the same amount of copper the
relationship between magnetic field and electrical power is fixed too.

What does change is the impedance (resistance and inductance) of the winding, which is proportional to
the square of the number of turns.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

DROBNJAK

Guys, thanks for all the input.

Because everything is inter-dependant I don't yet know what my parameters are. But broadly speaking:


- DC or AC: Its both, AC with DC offset. AC's frequency broadly from 1,000Hz to 10,000Hz. DC offset not more than 5 V DC. Most likely DC offset 1.0..2.0V DC. AC amplitude, say 2.0V AC peak-to-peak.

- Voltage - possibly I need two solutions:

1) 2x AA battery, so V= 2x 1.2 = 2.4V DC @ about Imax < 1.0A,

2) LiPo battery, so V= 7.4V DC @ Imax < 6.0A

- transformer or electromagnet? Hmmmm, something in between ;-)

  I need to bring magnetic field to certain level quickly hold it and drop it. And so on 1,000 to say 5,000 times per second.

MarkT

So you'll need a laminated core then.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

DROBNJAK

So you'll need a laminated core then.
confirmed. Most likely I will start with nanocrystaline stripss, like mu-metal or permaloy 80. They saturate quickly. But if they don't work out, I can go back to ferrites.

krupski

Guys, thanks for all the input.

Because everything is inter-dependant I don't yet know what my parameters are. But broadly speaking:


- DC or AC: Its both, AC with DC offset. AC's frequency broadly from 1,000Hz to 10,000Hz. DC offset not more than 5 V DC. Most likely DC offset 1.0..2.0V DC. AC amplitude, say 2.0V AC peak-to-peak.

- Voltage - possibly I need two solutions:

1) 2x AA battery, so V= 2x 1.2 = 2.4V DC @ about Imax < 1.0A,

2) LiPo battery, so V= 7.4V DC @ Imax < 6.0A

- transformer or electromagnet? Hmmmm, something in between ;-)

  I need to bring magnetic field to certain level quickly hold it and drop it. And so on 1,000 to say 5,000 times per second.

OK, I'll ask again. What are you trying to make?  From what you said about making a field then dropping it quickly, it sounds like a spark or at least high voltage generator or maybe an inverter.

Concerning your last post, do you know anything at all about electromagnetics? You mention "mu-metal" and "permalloy" and "ferrite" as if they are all interchangeable.

With ferrite cores alone, there are more types (composition, working frequency, power handling capacity, etc...) than you can shake a stick at. What kind of "ferrite" do you think you can use?

Unless it's a deep, dark secret, we need to know what you want to accomplish, otherwise no one here can give you ANY useful information.
Gentlemen may prefer Blondes, but Real Men prefer Redheads!

DROBNJAK

#9
May 22, 2017, 05:09 pm Last Edit: May 22, 2017, 05:10 pm by DROBNJAK
I prefer Redheads as well ;-)

Lets say something like Ultraperm 80 alloy, on a frequency between 1,000 and 5,000Hz, with very low level of saturation, but high permeability. I just want to reach high magnetic flux density B and than quickly reverse, with AC.


jackrae

So time for you to start some experimental work.

DROBNJAK

Yes Sir.

Thanks to everybody for the input.

DROBNJAK

#12
May 24, 2017, 07:24 pm Last Edit: May 24, 2017, 07:31 pm by DROBNJAK
Here it is, I've done some simulations in FEMM v4.2. Same geometry, same magnetic flux density B= 8.00mT, but one coil was made from 133 turns of 16AWG, another from 931 turns of 24AWG.

Differencies are not big.



24AWG coil:

+ better flux linkage, + Needed less current, + Needed less power, +
- had 7 times more turns, if you are winding coil by hand keep that in mind,
- needed 178m of wire, as opposed to just 25m for 16AWG,
- had a much bigger resistance and needed 6 times more voltage to drive its current,



16AWG coil:

+ almost 50 times less inductance. Now this can be both good and bad, depending on the application.
+ it needed about 7 times less windings.
+ much less of a voltage drop, about 6 times.
+ I am guessing here, but 16AWG would be less noisy than a thinner wire.
- dissipated slightly more power, but it would have better cooling because of bigger air gaps between the wires.

I personally like 16AWG better. Much less work.

Take your pick ;-)

N.B.
If you wanted to play with FEMM 4.2 models, here are the files: Test-Wires_16AWG-vs-24AWG.zip

MarkT

The impedances change as the square of the number of turns but make no difference at all
to the magnet performance since for a lower impedance coil you drive with a lower impedance
to match.  Only at RF where the inter-winding capacitance and skin-effects become important does
the difference change the performance of the magnet (less turns for higher frequencies).

Select a winding impedance that's convenient for your supply and forget about these variations.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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