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Motor Winds and Turns explained.

Discussion in 'Electric RC Talk' started by militarymaxx, May 29, 2004.

  1. militarymaxx

    militarymaxx RCNT Addict

    Here are some basic definitions to help sort out some of the options. Enjoy !

    Turns - The number of times the wire is wrapped around the armature. If you decrease the turns, the motor becomes more efficient, can pull more current, has a higher RPM but with less torque. So in very basic terms, in your head you can remember that turns equates to RPM. But high RPM generally means low torque.

    -The higher the number of turns, the lower the power of the motor but a higher RPM.

    -The lower the number of turns, the higher the power of the motor but a lower RPM.

    But this simple view of things can be changed slightly by the number of windings...

    Winds - The number of wires that is used for each winding around the armature. For complicated reasons, electrons flow with less resistance on the surface of a conductor. (This is why good quality speaker wire always has "stranded" wire rather than a solid copper core. Conduction and Valence bands, Covalent bonding, blah blah blah) So if you replace a single large copper wire with several smaller ones, you have effectively increased the total surface area of the conductor and most likely dropped the overall weight of the motor. So the more winds, the more efficient the motor is in general terms.

    So why not choose a 10 turn single? You could, but at the cost of lowered run time due to lowered resistance which equates to higher current draw.
     
  2. Rolex

    Rolex I've fallen and I can't get up Staff Member Veteran

    Takes me back to my time in the service when I spent all of my money at the slot car track in town. We would buy cheap motors, open them up, remove the wiring, and rewind them, epoxy them, polish them and balance them. I seem to recall that however we wanted them to behave, we only used 28 ga. to 32 ga. wire, with the 32 being the wire of choice for torque. After a test run, gears would be changed accordingly.
    Heavy wire, less winds, more RPMs. Thin wire, more winds, greater torque.
     
    Last edited: Oct 6, 2007
  3. Lessen

    Lessen Super Awesome! Supporter

    ooooh.. this should be a sticky. I've been looking for an explanation of winds for half an hour. yay for search!
     
  4. helotaxi

    helotaxi RCNT Basher

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    The wind explanations doesn't make sense. Skin effect (what causes current to flow on the surface of the conductor) doesn't become appreciable until the frequency is in excess of 100,000 hz. In a motor that equates to 100,000 rpm. What does matter for resistance is the cross sectional area of the wire. What makes a difference in a motor with winds is the effect that the change in inductance caused by the multiple strands of wire wrapped around each other has on how the current flows into the motor. The higher inductance reduces the initial current spike that gives a motor its start-up torque. The addition of the winds makes the onset of power much smoother and the motor more controllable at the cost of initial acceleration. As the motor spins up the inductance plays a smaller part in the total impedance of the motor and the max RPM ends up being quite similar between motors with the same number of turns but different winds since the total cross sectional area of the wire in the motor windings is very close to the same. The higher winds gets slightly better run time under race conditions because the initial current spike on throttle application is reduced.
     

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