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ron_o
Moderator


United Kingdom
1052 Posts

Posted - February 08 2012 :  03:08:42  Show Profile Send ron_o a Private Message  Reply with Quote
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 10-7

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 10-4 metres^2 ( equivalent to core of 3/4 inch dia )

F = 0.7^2 x 2.835 x 10-7 / 2 x 4 x Pi x 10-7

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  Show Profile  Visit hkalan's Homepage Send hkalan a Private Message  Reply with Quote
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
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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 08 2012 :  05:10:54  Show Profile Send ron_o a Private Message  Reply with Quote
Hi Alan

Thank you for your kind offer of a javascript calculator, sounds good to me.

Lets see what we can do !

ron
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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 09 2012 :  03:11:45  Show Profile Send ron_o a Private Message  Reply with Quote
Ampere-turns

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
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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 15 2012 :  03:06:28  Show Profile Send ron_o a Private Message  Reply with Quote
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 ampere-turns per metre

Example

If , F = 100 ampere-turns and winding length = 2 cm ( 0.02 metres ) then H = 100 / 0.02 = 5000 ampere-turns per metre.
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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 25 2012 :  14:57:44  Show Profile Send ron_o a Private Message  Reply with Quote
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

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hkalan
Senior Member



Hong Kong
1019 Posts

Posted - February 25 2012 :  21:29:29  Show Profile  Visit hkalan's Homepage Send hkalan a Private Message  Reply with Quote
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

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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 26 2012 :  03:53:48  Show Profile Send ron_o a Private Message  Reply with Quote
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
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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 26 2012 :  04:52:46  Show Profile Send ron_o a Private Message  Reply with Quote
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

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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 26 2012 :  04:59:26  Show Profile Send ron_o a Private Message  Reply with Quote
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

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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 26 2012 :  05:06:05  Show Profile Send ron_o a Private Message  Reply with Quote
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

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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 26 2012 :  05:09:20  Show Profile Send ron_o a Private Message  Reply with Quote
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
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Magneticitist
Senior Member



USA
681 Posts

Posted - February 26 2012 :  19:51:24  Show Profile  Visit Magneticitist's Homepage Send Magneticitist a Private Message  Reply with Quote
hey Ron, your input is much appreciated as always, i just wish i knew how to speak insanely-smart-robot

[on the gravy train with biscuit wheels]
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ron_o
Moderator



United Kingdom
1052 Posts

Posted - February 27 2012 :  17:00:55  Show Profile Send ron_o a Private Message  Reply with Quote
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 " insanely-smart-robot" , lol
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jackdawson
New Member



USA
3 Posts

Posted - July 14 2012 :  00:19:02  Show Profile Send jackdawson a Private Message  Reply with Quote
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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