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Old Mar 13, 2011, 02:48 PM
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DC motor winding turns, wire diameter calculation.?

hi to all of participiants,

i have 12v permanent magnet dc motor.i know revolution, it s windings turns, and wire diameter. forexample this motor parameters are:
Voltage: 12v
rpm :2000 rpm
windings turns: 20
wire diameter:0.60mm

my question is this: if i want the revolution of that motor 2500 rpm in same tork. How must i change the parameters? i mean what is the optimum design? But current must not rise so much. i want to learn optimum design formulas?relationship between winding turns and wire diameter in the same load.
Thanks,
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Old Mar 13, 2011, 07:41 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,995 Posts
For the brushless outrunners we use (and inrunners too I think) we can use a wonderful (and free) turn calculator that one of our forum members has developed. That is Manuel_V's Turn Calculator 5 which can be downloaded here:

http://www.rcgroups.com/forums/showp...0&postcount=17

With that, you can enter the turn count and termination type (Delta or Wye) that you have now and it will give you the Kv for other turn counts and for the other types of wind we do. I don't know if that will work for your motor or not, it is an outrunner?

The attached image is an example of a recent use I made of it to decide the turn count for a rewind. If you motor of a similar construction to out brushless outrunners maybe that will work for you too.

With the same wind and termination, adding turns lowers the Kv and reducing the number of turns raises it. The torque will be similar I think but not exactly the same.

You can run the spreadsheet with the free OpenOffice.org Calc application if you do not have Microsoft's Excel.

Jack
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Old Mar 14, 2011, 09:43 AM
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Dear my motor is permanent magnet brushed motor. i cant see any information illusturated with wire diameter in that program. i want to know what kind of diameter is available for my optimum design. i want to realize that how must i change my parameters (winding turns, wire diameter) and my motor will work effectively. by the way in your program there are some expressions like termination (d, y) LRK DELta etc.. i have only dc motor. it s not brushless. Do you have any excel file for me? permanent magnet dc brushed motor 12 v, 24v. i have some effecvite motors in same size(body lengh, lamination diameter etc.) but when i try to construct new motor speed i dont know how to do it. Sometimes current is so high.. sometimes when the motor works no-load condition and when it works in load so my motor falls down so much (example:no load 3000 rpm- in load:2000rpm. decreasing is so high!!!). i want to know how can i construct optimum design. (i can change winding turns and wire diameter.) Anyone can help me?
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Old Mar 14, 2011, 10:28 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,995 Posts
Quote:
Originally Posted by mir_as82 View Post
Dear my motor is permanent magnet brushed motor. i cant see any information illusturated with wire diameter in that program. i want to know what kind of diameter is available for my optimum design. i want to realize that how must i change my parameters (winding turns, wire diameter) and my motor will work effectively. by the way in your program there are some expressions like termination (d, y) LRK DELta etc.. i have only dc motor. it s not brushless. Do you have any excel file for me? permanent magnet dc brushed motor 12 v, 24v. i have some effecvite motors in same size(body lengh, lamination diameter etc.) but when i try to construct new motor speed i dont know how to do it. Sometimes current is so high.. sometimes when the motor works no-load condition and when it works in load so my motor falls down so much (example:no load 3000 rpm- in load:2000rpm. decreasing is so high!!!). i want to know how can i construct optimum design. (i can change winding turns and wire diameter.) Anyone can help me?
I did not know enough about your motor, or motors in general, to realize that the spreadsheet would not work for you.

On our motors the turn count determines the Kv and we generally use the largest size of wire that will fit on the stator arms. That will let us get the most copper density and surface area. The maximum current capacity is usually by testing after the winding, when it gets too hot it is too much.

Good luck with it, maybe someone with more knowledge will come along.

Jack
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Old Mar 14, 2011, 03:37 PM
Scratch builder
USA, PA, Telford
Joined Apr 2004
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As Jack said, speed comes from turns. Changing turns is simply a ratio of what you have to what you want. 2000/2500 = .8 .8 x 20 turns = 16 turns of .7mm wire (.7 dia. comes from: 1.25 x the area of .6mm wire, 1.25 is the inverse of .8)

The same load and volts on this new winding will make the amps go up.

Our motors operate most efficient at 75 to 80% of no load RPM.
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Old Mar 15, 2011, 09:19 AM
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thanks for your reply.i will try your suggestion later.. But i want to explain my aim. when the winding turns of motor is changed so current of motor rises so much.... if i wind less turn and higher diameter of wire so motor falls down when it s on load(no load 3000 on load:2000. i dont want motor falls down so much. i want to find out which point is the best point for my motor.(turn, wire diameter).i mean the most effective point. i want to adjust turns and wire diameter on that point.)
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Old Mar 15, 2011, 11:18 AM
Scratch builder
USA, PA, Telford
Joined Apr 2004
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The windings can't be changed from that point. If your no load speed is 3000 rpm and your load drops it to 2000 then the motor is not powerful enough. Changing the winding will not help. The winding determines what voltage causes 3000 rpm. Based on the supplied motor data, are you running at 18 volts? Is the battery voltage dropping off too much because of the amp load?
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Last edited by KenSt; Mar 15, 2011 at 11:31 AM.
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Old Mar 15, 2011, 01:09 PM
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Originally Posted by KenSt View Post
The windings can't be changed from that point. If your no load speed is 3000 rpm and your load drops it to 2000 then the motor is not powerful enough. Changing the winding will not help. The winding determines what voltage causes 3000 rpm. Based on the supplied motor data, are you running at 18 volts? Is the battery voltage dropping off too much because of the amp load?
My motor is permanent magnet dc motor. really it drops like this. connect fan it's shaft but it drops from 3000 to 2000. i need to find out maximum efficiency point in that sized motor. how ca i find?
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Old Mar 15, 2011, 02:24 PM
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The best efficiency point of your motor is between 2250 to 2400 RPM. (see last sentence of post #5) The 2000 RPM you're getting isn't terrible, the motor is just a little below the best it can do efficiency wise.

See this link. http://www.peakeff.com/GraphKIR.aspx

Notice that any motor graph will have the efficiency peak around the pertectages of no load speed I mentioned above. The actual efficiency of your motor must be graphed to see how good it is.
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Old Mar 15, 2011, 05:20 PM
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Originally Posted by KenSt View Post
The best efficiency point of your motor is between 2250 to 2400 RPM. (see last sentence of post #5) The 2000 RPM you're getting isn't terrible, the motor is just a little below the best it can do efficiency wise.

See this link. http://www.peakeff.com/GraphKIR.aspx

Notice that any motor graph will have the efficiency peak around the pertectages of no load speed I mentioned above. The actual efficiency of your motor must be graphed to see how good it is.
i have already checked your link. By the way weight is empty armature weight? or armature weight with windings? or total motor weight with body, bearings, covers, etc..?
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Old Mar 15, 2011, 05:32 PM
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Another question is: Must i measure V0, I0, RPM0 and V1, I1, RPM1 in the same winding turns?
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Old Mar 15, 2011, 08:34 PM
Scratch builder
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Joined Apr 2004
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Total motor weight. The whole thing contributes to heat dissipation.

The motor characteristics are measured as a complete running motor. Go to the site and read "Find Constants" They are using propellers as a load point instead of a dynamometer. This is fairly accurate and about the only reasonable way a modeler can do it. It is important to use a prop that loads the motor as they say "at the planned" load you intend to use. Skewed results come from a prop that runs too close to no load values.

Brushed and brushless DC motors behave the same to the physical effects of load, voltage, efficiency, amps, RPM drop etc...
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Old Mar 16, 2011, 01:29 AM
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Total motor weight. The whole thing contributes to heat dissipation.

The motor characteristics are measured as a complete running motor. Go to the site and read "Find Constants" They are using propellers as a load point instead of a dynamometer. This is fairly accurate and about the only reasonable way a modeler can do it. It is important to use a prop that loads the motor as they say "at the planned" load you intend to use. Skewed results come from a prop that runs too close to no load values.

Brushed and brushless DC motors behave the same to the physical effects of load, voltage, efficiency, amps, RPM drop etc...
propeller is gear or fan? and must i measure this attributes in same wire diameter and winding turns? forxample i measured Io(no load) in 0.65 mm wire and 15 turns,13V, than for V1, I1 and RPM1 i measured the motor in 0.85 mm wire 12 turns, 13V. Than for V2, I2 and RPM2 i measured motor in 0.80mm 14 turns,13 V. is it true way? or must i measure all of parameters for Kv in same wire dia. and same turns?(Io, I1, I2, V1, V2, RPM1, RPM2 in same wire dia. and turns?)
My last question is: Do you have that program? can i download it? or do you have formulas of that program?
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Old Mar 16, 2011, 08:47 AM
Scratch builder
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Propeller is fan.

All parameters must be measured with the same wire and turns as an assembled motor.

The program is in the link I provided. Follow their directions. The program compares the no load parameters and the loaded motor (using a fan) parameters. It then graphs the results so you can see all the parameters besides the ones you entered.

Since I already know where the most effecient point is based on speed, I just use 75 to 80% of no load. This will not tell you how efficient the motor is but it will tell you when to stop increasing the fan size. (propeller diameter or pitch)
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Old Mar 16, 2011, 09:07 AM
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Originally Posted by KenSt View Post
Propeller is fan.

All parameters must be measured with the same wire and turns as an assembled motor.

The program is in the link I provided. Follow their directions. The program compares the no load parameters and the loaded motor (using a fan) parameters. It then graphs the results so you can see all the parameters besides the ones you entered.

Since I already know where the most effecient point is based on speed, I just use 75 to 80% of no load. This will not tell you how efficient the motor is but it will tell you when to stop increasing the fan size. (propeller diameter or pitch)
My friend do you have any e-book about designing permanent magnet dc motor? or do you have any formulas which is illustrated with real aplications?
(12 Volt, 24 Volt permanent magnet dc motors.). i want to know how i can design motor. phycially and electrically. (lamination thickness, armature diamater, lamination package lenght, magnetic field strength. About electrtical, wire diameter, winding turns numbers. etc..). Do you have any information about this? or do you know any book? Thanks for your help. You are really good helper.
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