Author 
Topic 

ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 08 2012 : 03:08:42

I hope to post several useful equations ( + examples ) for coil design.
Pull / Lift of an electromagnet.
F = B^2 x A / 2 u0
F = force in Newtons
u0 = 4 x Pi X 107
B = core flux density in Tesla
A = pole face area in metres^2
Pi = 3.142
Example
B = 0.7 Tesla
A = 2.835 x 104 metres^2 ( equivalent to core of 3/4 inch dia )
F = 0.7^2 x 2.835 x 107 / 2 x 4 x Pi x 107
F = 55.27 Newtons
To convert Newtons to lifting power ( in Kg ) divide by 9.81
Lifting power = 55.27 / 9.81 = 5.634 kg

Force in Newtons at a given distance ( in metres )
F = ( N x I )^2 x u) x A / 2 x g^2
where
g = air gap in metres
I = current in Amps
N = Number of turns of wire in coil
I will also be writing a small BASIC program to do all the "hard work" in the near future
NB program will be written in the free BASIC program "justBasic"
ron


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hkalan
Senior Member
Hong Kong
1019 Posts 
Posted  February 08 2012 : 05:00:58

Hello Ron,
Those formulas are great.
I need to learn how to use them... LOL
If you have time to cooperate with me. I could make a calculator for each of the formula on the IAEC website You must be logged in to see this link. using Javascript.
Alan 


ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 08 2012 : 05:10:54

Hi Alan
Thank you for your kind offer of a javascript calculator, sounds good to me.
Lets see what we can do !
ron 


ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 09 2012 : 03:11:45

Ampereturns
Here, we need to find the resistance of the average turn and decide upon the coils working voltage.
Firstly , measure both the inner( core/former ) and outer diameters of the coil.
Average turn diameter = ( ( outer diameter  inner diameter ) / 2 ) + inner diameter
Example
outer dia = 4 inches , inner dia = 1 inch
Average turn diameter = (( 4  1 ) / 2 ) + 1 = ( 3 /2 ) + 1
= 1.5 + 1
Average turn diameter = 2.5 inches
Average turn length = average turn diameter x 3.142
= 2.5 x 3.142 = 7.855 inches
The next step is to calculate the resistance of the average turn length ( resistance per unit lentgh can be obtained for copper wire data tables i.e as ohms per foot )
Resistance per average turn = ( average turn length ( in inches ) / 12 ) x ohms per foot
Example
Lets assume that our resistance worked out to be exactly one ohm per average turn length.
Using a 12 volt supply and Ohms Law
Current in amps = voltage / resistance = 12 / 1 = 12 amps
so 1 turn at 12 amps = 12 ampere turns.
The following are all expansions /equivalents to 12 ampere turns
10 Turns @ 1.2 amps
100 Turns @ 0.12 amps
1000 Turns @ 0.012 amps
ron 


ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 15 2012 : 03:06:28

Magnetomotive Force , F
F = I x N , where I = average current flowing through cil and N = number of turns
Magnetic Field Strength , H
H = F / l , where l = length of winding in metres . Units are ampereturns per metre
Example
If , F = 100 ampereturns and winding length = 2 cm ( 0.02 metres ) then H = 100 / 0.02 = 5000 ampereturns per metre. 


ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 25 2012 : 14:57:44

This ai a very simple/crude coil wire length calculator program , written in JustBasic.
print" Total Wire Length needed" print input" Enter former core diameter ";d print input" Enter diameter of wire ";ab print input" Enter number of layers ";totallayers print input" Enter number of turns on first layer ";nturns print
ax = 0 ax = ((ab^2)((ab/2)^2))^0.5
wlength = 0 wlength = nturns * 3.14159 * d
print "1", wlength
for layer = 2 to totallayers if layer / 2  int(layer/2) > 0 then
wlength = wlength + ( nturns  1 ) * 3.14159 * (( 2 * ( ab/2 + (((( layer * 2 )  1 ) / 2 ) * ax ))) + d )
print layer , wlength else
wlength = wlength + ( nturns ) * 3.14159 * (( 2 * ( ab/2 + (((( layer * 2 )  1 ) / 2 ) * ax ))) + d )
print layer , wlength
end if
next layer
print
print "Total wire length needed ";wlength
stop
ron



hkalan
Senior Member
Hong Kong
1019 Posts 
Posted  February 25 2012 : 21:29:29

Hey Ron,
I will try to put that into JavaScript and put that into a dedicated "Wire Length" Calculator for the IAEC website !!!
Thanks for all the data !
Alan



ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 26 2012 : 03:53:48

Hi Alan
That would be great ! , thank you Alan
Please remember however that all these type(s) of calculations do not allow for the thickness of insulation if wire gauge/diameter is used , those values are for the size of the copper only. This is especially so when fine/small wire is used.
ron 


ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 26 2012 : 04:52:46

Program to calculate flux density falloff vs distance
print print"MAGNETIC FLUX DENSITY Vs DISTANCE FROM MAGNET FACE"
Input "Enter residual flux density of magnet : ";Br print input"Enter diameter of magnet ( in metres ) : "; disc print input"Enter thickness of magnet ( in metres ) : "; L print R = disc / 2
print" distance from  flux density" print" poleface (metres) " print for x = .001 to .01 step .001
Bx = Br/2 * (( x + L) / (( R^2 + (x + L )^2)^.5)  ( x / ( R^2 + x^2)^.5)) print using ("###.###" , x) , :print using ("###############" ,Bx)
next x stop



ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 26 2012 : 04:59:26

A practical example program of generator coil output
Please note if this program fails to work please let me know as it might exceed the forums text editors line length , if so i will amend the code to fit
print
print"MAGNETIC FLUX DENSITY Vs DISTANCE FROM MAGNET FACE" print print"ALL UNITS ARE IN METRES" PRINT
Input "Enter residual flux density of magnet : ";Br print input"Enter diameter of magnet : "; disc print input"Enter thickness of magnet : "; L PRINT INPUT"Enter number of magnets on rotor : ";numbermagnets print input"Enter number of turns on one generator coil : "; n print input"Enter diameter of coil : "; dia print input"Enter depth of coil : "; l PRINT input"Enter diameter of ferrite core : "; core core = core / 2
R = disc / 2
rad = dia/2
print print PRINT"_______________________________________________________________" PRINT print" MAGNETIC FLUX DENSITY Vs DISTANCE FROM MAGNET FACE" PRINT PRINT" Metres Gauss" PRINT"________________________________________________________________"
for x = .001 to .01 step .001
Bx = Br/2 * (( x + L) / (( R^2 + (x + L )^2)^.5)  ( x / ( R^2 + x^2)^.5)) print,:PRINT using ("###.###" , x) , :print using ("###############" ,Bx) next x
print print
print"______________________________________________________________________________" print print" POWER OUTPUT FOR AMPS INPUT TO RUN / DRIVE COIL" print"______________________________________________________________________________" print print" AMPS H(amp/turns) B(Tesla) F(Newtons) LIFT(KG) m W b" print
rem n = 300 rem l = .007
for i = .1 to 1 step .1 h = 0 h = i * n / l
b = 0 b = 0.0000377 * h
f = 0 f = b * b * 389000 * 3.142 * rad * rad
k= 0 k = f / 9.81
w = 0 w = b * 3.142 * core * core
print using ("###.###" , i ),:print using ( "########" , h ) , : print using ( "####.#####" , b ) ,: print using ("####.#####" , f ) , print using ("####.#####" , k ),:print w next i print print print
print" ___________________________________________________________________________________________________________" print print"  AC OUTPUT VOLTAGE FROM COIL PAIR @ STATED RPM " print" ___________________________________________________________________________________________________________" print" Air Gap Total Gap B(Gauss) 1600 rpm 1800 rpm 2000 rpm 2200 rpm 2400 rpm"
Bx = 0 rem Br = 9940 rem L = 0.01 rem R = 0.0
value = 0 value = numbermagnets * n * 3.14159 * R * R * 2
for z = .001 to .015 step .0005 x = 0 x = z + .0025
Bx = Br/2 * (( x + L) / (( R^2 + (x + L )^2)^.5)  ( x / ( R^2 + x^2)^.5)) print using ("####.####", z ) ,:print using ("####.####" , x ),: print using ("#######.#" , Bx ), Bx = Bx / 10000 print using ("#######.##" , (Bx * value / .0375 ) ),: print using ("#######.##" , ( Bx * value / .0333 )),: print using ("#######.##" ,( Bx * value / .03 )), print using ("#######.##" , ( Bx * value / .0272) ),: print using ("#######.##" , ( Bx * value / .025) ) Bx = 0
next z
print print
print" ___________________________________________________________________________________________________________" print print"  DC OUTPUT VOLTAGE FROM COIL PAIR @ STATED RPM " print" ___________________________________________________________________________________________________________" print" Air Gap Total Gap B(Gauss) 1600 rpm 1800 rpm 2000 rpm 2200 rpm 2400 rpm"
Bx = 0 rem Br = 9940 rem L = 0.01 rem R = 0.01 for z = .001 to .015 step .0005 x = 0 x = z + .0025
Bx = Br/2 * (( x + L) / (( R^2 + (x + L )^2)^.5)  ( x / ( R^2 + x^2)^.5)) print using ("####.####", z ) ,:print using ("####.####" , x ),: print using ("#######.#" , Bx ), Bx = Bx * 1.414 / 10000 print using ("#######.##" , (Bx * value / .0375 ) ),: print using ("#######.##" , ( Bx * value / .0333 )),: print using ("#######.##" ,( Bx * value / .03 )), print using ("#######.##" , ( Bx * value / .0272) ),: print using ("#######.##" , ( Bx * value / .025) ) Bx = 0
next z stop



ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 26 2012 : 05:06:05

print
print" Optimum Design for SS Bedini Coil" print
input" Enter wire diameter ( in millimetres ) "; diawire print print print" # layers Former OD Former ID Wind Space Wire Length " for layers = 2 to 15 m = diawire * layers * 3 c = diawire * layers id = m  c od = m + c totalwire = 0 wirelayer = 0 for x = 1 to layers wirelayer = wirelayer + 3.142 * layers * ( id + (( x  1 ) * x * diawire )) totalwire = totalwire + wirelayer next x print print using("########.##" , layers ), :print using("########.##" , od ),: print using("########.##" , id ), :print using("########.##" , c ), print using("########.##" , totalwire / 1000 ) rem print layers , od , m , c , id , totalwire next layers stop



ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 26 2012 : 05:09:20

I have just tried cutting and pasting a program and the forum editor sometimes ( don't know yet only sometimes ! ) sees to remove spaces in the print formating
ron 


Magneticitist
Senior Member
USA
681 Posts 
Posted  February 26 2012 : 19:51:24

hey Ron, your input is much appreciated as always, i just wish i knew how to speak insanelysmartrobot
[on the gravy train with biscuit wheels] 


ron_o
Moderator
United Kingdom
1052 Posts 
Posted  February 27 2012 : 17:00:55

Hi Ryan
If it helps the programs i wrote the programs to investigate the RomeroUK motor/generator , i have others such as the Bedini Ferris wheel motor. BTW its time to worry when the programs answer back in " insanelysmartrobot" , lol



jackdawson
New Member
USA
3 Posts 
Posted  July 14 2012 : 00:19:02

There are e lot of things are made of electromagnet as electrical coils,tattoo machine coils,pick and place vacuum pumps etc.If you want to buy electromagnet then there are a lot of options that are available to it.but this is the best way to save money because the quality of these coils are very good. 



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