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Bldc design from scratch

  1. Aug 12, 2009 #1

    could someone guide me through the steps of how I would go about designing a bldc motor, knowing only the following requirements;

    a) Power 300W
    b) voltage 24V
    c) Torque 40 Nm
    d) RPM 180
    e) Max external dia = 254mm
    f) Max length = 90 mm

    So now I need to know;
    1) How many poles do I need? and why?
    2) How many teeth? and why?
    3) How many windings? and why?
    4) Of what diameter wire? and why?
    5) What dimension magnets? and why?

    Would much appreciate if you can get me started.
    I'm sure I can take it from there

  2. jcsd
  3. Aug 12, 2009 #2
    Hello Sunil-
    This will be very difficult design. 40Nm torque at 180 RPM is about 750 watts (1 HP) output power. A 300 watt motor will not be adequate.
    Brushless dc motors are very difficult motors to design. I suggest you buy a commercial gearmotor.
    Bob S
  4. Aug 12, 2009 #3
    Thanks bob,

    We are currently using a commercial gear motor. It is heavy, clunky and inefficient.
    Also it dictates much of the design because of it's size.

    I realize that it's not an easy undertaking, but I feel that I have to try.

    if my power has to be 750W, what's the next step?
  5. Aug 13, 2009 #4
    Hi Sunil-
    Check that you really need 180 RPM at 40 Nm = 750 watts = 1 HP
    I suspect that your motor will have to run at maybe 2500 RPM to minimize torque (and motor size) at 1 HP, so you will have a roughly 15:1 gearbox.
    I suggest talking to Bodine Electric Motor engineers, and maybe DD Electric Motor (ddmotorsystems.com).
    Bob S.
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