Hello, all
A friend and I are currently building a high current coil gun for our
senior design project at the University of Maine. Recently we have been
trying to optimize the coil design, and I believe we are relatively
close. Here is what we have so far:
We know that amp-turns (NI ? a.k.a. Magneto-Motive Force) is the most
important factor when designing the coil.
Our power supply is a bank of large electrolytic capacitors (47 mF)
charged to 340 volts. We are also setting a current limit of 100 Amps,
even though the HVIGBT we have is rated to 400 amps continuous. Based on
these numbers our coil resistance has to be 3.4 Ohms. So basically what
we have found so far is to get the highest NI do the following steps:
1) Select the largest wire you can afford
2) Wind as many layers onto the barrel as needed to make the
necessary resistance.
What we are not taking into account is the length of the barrel, and the
thickness of the coil winding. Right now we have a barrel (and
projectile) fixed at 1 foot long. And the coil windings have no limit.
At a certain point the distance from the center of the coil has to start
making a big difference correct? How do you determine the best length
and coil windings? By shrinking the length of the barrel you create
more force on the projectile, but that force is over a shorter distance.
Also how do you calculate inductance with J.A? I have looked at several
examples and it does not make sense to me. Included is the femm model of
our coil, and the matlab script I wrote to help us determine the optimal
number of layers. Thanks in advance for your help,
Samuel Ace Winchenbach
University of Maine Electrical Engineering
swinchen@xxxxxxxxxxxxxx
/==== snip ====/
Our barrel is 5/16? in diameter, a foot long piece of garolite. It has
an inside diameter of ¼?. We are currently using 18 AWG magnet wire,
with 0 series resistance.
EDU>> help CoilOpt
function CoilOpt(
BarrelDiam (in),
CoilLength (ft),
WireDiam (mm),
ResPerkm (Ohms/km),
SeriesRes (Ohms),
Voltage (Volts),
CurrentLimit (A)
)
EDU>> CoilOpt((5/16),1,1.0668,20.9,0,340,100)
----- Non-Optimized Coil Packing -----
|
| NI (Amps*Turns): 2.783180754224393e+005
| NI/L (Amps*Turns/CoilLength): 9.131170453492102e+005
| J (Amps/Meter^2): 8.559402374851990e+007
| CoilWidth (Meters): 0.010668000000000
|
| Resistance (Ohms): 3.481627984561275
| Current (Amps): 97.655465060504994
|
| WireUsed (ft): 546.538946954199220
| Number of Layers: 10
| Turns Per Layer: 285
| N (Total Turns): 2850
|
--------------------------------------
----- Optimized Coil Packing -----
|
| NI (Amps*Turns): 2.838475142859972e+005
| NI/L (Amps*Turns/CoilLength): 9.312582489698071e+005
| J (Amps/Meter^2): 9.036465157159652e+007
| CoilWidth (Meters): 0.010305559007572
|
| Resistance (Ohms): 3.755185253889620
| Current (Amps): 90.541471861562101
|
| WireUsed (ft): 589.481415986892440
| Number of Layers: 11
| Turns Per Layer: 285
| N (Total Turns): 3135
|
----------------------------------
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<div class=Section1>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hello, all<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>A friend and I are currently building a high current coil
gun for our senior design project at the </span></font><st1:place><st1:PlaceType><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>University</span></font></st1:PlaceType><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> of </span></font><st1:PlaceName><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Maine</span></font></st1:PlaceName></st1:place><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>. <span
style='mso-spacerun:yes'> </span>Recently we have been trying to optimize the
coil design, and I believe we are relatively close.<span
style='mso-spacerun:yes'> </span>Here is what we have so far:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We know that amp-turns (NI – a.k.a. Magneto-Motive
Force) <span class=GramE>is</span> the most important factor when designing the
coil.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Our power supply is a bank of large electrolytic capacitors
(47 mF) charged to 340 volts. <span style='mso-spacerun:yes'> </span>Weare
also setting a current limit of 100 Amps, even though the HVIGBT we have is
rated to 400 amps continuous. Based on these numbers our coil resistance has to
be 3.4 Ohms.<span style='mso-spacerun:yes'> </span>So basically what we have
found so far is to get the highest NI do the following steps:<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1;
tab-stops:list .5in'><![if !supportLists]><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial;mso-fareast-font-family:Arial'><span
style='mso-list:Ignore'>1)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Select the
largest wire you can afford<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1;
tab-stops:list .5in'><![if !supportLists]><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial;mso-fareast-font-family:Arial'><span
style='mso-list:Ignore'>2)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Wind as many
layers onto the barrel as needed to make the necessary resistance.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>What we are not taking into account is the length of the
barrel, and the thickness of the coil winding.<span style='mso-spacerun:yes'>
</span>Right now we have a barrel (and projectile) fixed at 1 foot long. <span
style='mso-spacerun:yes'> </span>And the coil windings have no limit.<span
style='mso-spacerun:yes'> </span>At a certain point the distance from the
center of the coil has to start making a big difference correct?<span
style='mso-spacerun:yes'> </span>How do you determine the best length and coil
windings?<span style='mso-spacerun:yes'> </span>By shrinking the length of the
barrel you create more force on the projectile, but that force is over a
shorter distance.<span style='mso-spacerun:yes'> </span>Also how do you
calculate inductance with J.A?<span style='mso-spacerun:yes'> </span>Ihave
looked at several examples and it does not make sense to me. Included is the <span
class=SpellE>femm</span> model of our coil, and the <span class=SpellE>matlab</span>
script I wrote to help us determine the optimal number of layers.<span
style='mso-spacerun:yes'> </span>Thanks in advance for your help,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Samuel Ace <span class=SpellE>Winchenbach</span><o:p></o:p></span></font></p>
<p class=MsoNormal><st1:place><st1:PlaceType><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>University</span></font></st1:PlaceType><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> of </span></font><st1:PlaceName><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Maine</span></font></st1:PlaceName></st1:place><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> Electrical
Engineering<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><a href="mailto:swinchen@xxxxxxxxxxxxxx";>swinchen@xxxxxxxxxxxxxx</a><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>/==== snip ====/<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Our barrel is 5/16” in diameter, a foot long pieceof <span
class=SpellE>garolite</span>.<span style='mso-spacerun:yes'> </span>It has an
inside diameter of ¼”.<span style='mso-spacerun:yes'> </span>We are
currently using 18 AWG magnet wire, with 0 series resistance. <span
style='mso-spacerun:yes'> </span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>EDU>> help <span class=SpellE>CoilOpt</span><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span class=GramE>function</span>
<span class=SpellE>CoilOpt</span>(<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE>BarrelDiam</span> (in),<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE>CoilLength</span> (ft),<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE>WireDiam</span> (mm),<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE>ResPerkm</span> (Ohms/km),<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE>SeriesRes</span> (Ohms),<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>Voltage (Volts),<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span><span
class=SpellE>CurrentLimit</span> (A)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>EDU>> <span class=SpellE><span class=GramE>CoilOpt</span></span><span
class=GramE>(</span>(5/16),1,1.0668,20.9,0,340,100)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>----- Non-Optimized
Coil Packing -----<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>|<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| NI (Amps*Turns): 2.783180754224393e+005<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| NI/L (Amps*Turns/<span class=SpellE>CoilLength</span>):
9.131170453492102e+005<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| J (Amps/Meter^2): 8.559402374851990e+007<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| <span class=SpellE>CoilWidth</span> (Meters): 0.010668000000000<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>|<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| Resistance (Ohms): 3.481627984561275<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| Current (Amps): 97.655465060504994<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>|<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| <span class=SpellE>WireUsed</span> (ft):
546.538946954199220<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| Number of Layers: 10<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| Turns <span class=GramE>Per</span> Layer: 285<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| N (Total Turns): 2850<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>|<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span>--------------------------------------<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>----- Optimized Coil
Packing -----<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>|<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| NI (Amps*Turns): 2.838475142859972e+005<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| NI/L (Amps*Turns/<span class=SpellE>CoilLength</span>):
9.312582489698071e+005<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| J (Amps/Meter^2): 9.036465157159652e+007<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| <span class=SpellE>CoilWidth</span> (Meters):
0.010305559007572<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>|<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| Resistance (Ohms): 3.755185253889620<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| Current (Amps): 90.541471861562101<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>|<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| <span class=SpellE>WireUsed</span> (ft):
589.481415986892440<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| Number of Layers: 11<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| Turns <span class=GramE>Per</span> Layer: 285<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>| N (Total Turns): 3135<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>|<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span
style='mso-spacerun:yes'> </span>----------------------------------<o:p></o:p></span></font></p>
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