BLDC as generator drops current

Discussion in 'General Electronics Chat' started by flyinglawyer, Feb 1, 2015.

  1. flyinglawyer

    Thread Starter New Member

    Feb 1, 2015
    2
    0
    I am making a winch that will spool out line under tension. I've had success using an old brushed motor. I short the windings, so that when I unspool the line, the motor provides braking torque and line tension. The old motor is not powerful enough, so I upgraded to a stronger, brushless motor with 5000w power rating.

    Here's the problem: as I unspool the line from this motor, it builds torque until it reaches a certain value (130lb in my case), and then the current and torque suddenly drop to zero and then build up again, then drop again.

    The motor has 3 phases (which are shorted for the generator mode) and a 5-pin hall sensor connector (unused here). Here's the exact motor: http://www.aliexpress.com/item/Elec...-bicycle-5kw-ebike-hub-motor/32234157960.html

    Why is it dropping the current in generator mode? Do these motors have some kind of a built-in internal protection? I thought that there was nothing inside but windings and magnets (and halls), as this one uses an external 100Amp controller.

    Any thoughts would be appreciated.
    PS. Does this 3-phase brushless generate AC or pulse DC?
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    Could it be the controller cutting out?
     
  3. flyinglawyer

    Thread Starter New Member

    Feb 1, 2015
    2
    0
    The controller is disconnected.
     
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