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Power generated in regenerative braking

  1. Apr 1, 2014 #1
    The curve below is for a general electric motor drive(I'm guessing DC motor/possible 3phase induction). Would it be right to say that power generated in regenerative braking is the area under the curve in the 2nd quadrant ie the -ve M and +ve n(quadrant)?
    There are 2 portions of the diagram. The upper white portion symbolises overdrive in a electric motor. I guess this is not at rated power but at maximum power,since P_max≠P_rated.

    2.Regenerative braking would not gain energy in this area,am I correct?
    http://imageshack.com/a/img46/5958/91vr.gif [Broken]

    Also,if looked at in a more accurate way,there is a additional 3rd portion which is the normal drive.
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Apr 3, 2014 #2


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    What is M ?
    What is n ?
  4. Apr 3, 2014 #3
    M is the torque generated. n is the motor rpm
  5. Apr 3, 2014 #4


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    M is the torque generated. n is the motor rpm.

    Power = torque * RPM
    The sign of M*n is the direction of energy flow.

    Quadrants are defined by the signs of M and n.

    Energy will be consumed when the M*n product is positive.
    Energy will be re-generated when the M*n product is negative.
  6. Apr 22, 2014 #5
    A note: Regenerative breaking should only be applied if you actually hit the break pedal, if it occurs only when you ease up on the vehicles accelerator, it's far less efficient than a free-wheeling vehicle wich regenerates the kinetic energy put into it by its motor in a direct and much more efficient way by freewheeling.

    Think of a bicycle, you can pedal for a few seconds, then let it freewheel for a while, no regenerative system can compare to that in terms of energy effieciency.

    I have an electric car with regenerative braking, and an elctric scooter without it, and the last one is far better at preserving the energy put into it from the battery.
  7. Apr 23, 2014 #6
    commiesoft: But,regenerative braking could never applied for a freewheeling vehicle.The principle of regenerative braking (as I read) is that the electric motor/generator generates a rotating magnetic field in the opposite direction of the wheel + also generates electric energy at the same time.So,its doing 2 good things at the same time:1.generating electric energy 2.braking the wheel shaft. Hence,could never be used a freewheeling vehicle.'crusing' would never exist then.There's still a little doubt if the principle above I stated is correct.Please correct me if I was wrong.
  8. Apr 23, 2014 #7
    Hi marellasunny :) Regen braking can be applied to a freewheeling vehicle if it is applied only when hitting the brake pedal.

    In most e-mobiles regen 'braking' is applied when the driver eases up on the throttle, it has nothing to do with braking, it justs stops the vehicle from beeing able to act like a bicycle.

    On a bicycle you pedal for some moments, then rolls along when you can. This is actually direct regen of kinetic energy, and is far superior to any electrical system.

    Regen braking should not interfer with this much more efficient system, it should act as a compliment by beeing activated only when people hit the brake pedal. IMHO ;-)
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