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running motor as a generator

Morikeh Daramy
Intellectual 480 points
Other Parts Discussed in Thread: DRV8301

hi;

I am using;

tms320f28027f, c2000 launchpad with a maxon bldc motor and drv8301 motor drive.

I am trying to get the motor run as a generator whilst being driven by another motor.

My understanding of a BLDC motor would suggest that by simply driving the motor, I am already generating electricity.

However, I am looking at the schematic of the drv8301 motor drive, and I am seeing three of the six mosfets in the reverse direction.

My question is;

Am I supposed to control these MOSFET's in oder to produce a generator, or are they used for another purpose, such as allowing the motor to run in a reversed direction?

If they are used as part of a generator control system, can I be shown the direction towards the resources that will enable me to do this

Thanks

  • 0
    TI__Guru** 119670 points
    "I am already generating electricity."
    you are generating a back emf voltage on each phase

    "Am I supposed to control these MOSFET's in order to produce a generator"
    yes

    "resources that will enable me to do this"
    I would read more online from using 3-ph inverters as generators.
    If you just want to jump in to control, InstaSPIN-FOC is being used as it fundamentally is capable of controlling motoring and generating.
  • 0 in reply to ChrisClearman
    Intellectual 480 points
    "you are generating a back emf voltage on each phase"
    My understanding of an electric motor is that; it is both a motor and a generator at the same time.
    Driving it, induces a current in the phase windings
    Powering it, causes the rotor to rotate about its axis.

    I have driven the motor, and taken voltage reading from the power pins on the booster pack.
    The Launchpad becomes energied when the speed that the motor is driven at produces a "back emf?" proportional to approximately 6V.

    Is this not energy generation.
    I can't seem to wrap my head around putting power into the system, by altering the commutation sequence, in order to produce generate power.

    Even looking at the project 11b.c file, I can't seem to find the section of code that would allow me to alter the commutation sequence.

    "If you just want to jump in to control, InstaSPIN-FOC is being used as it fundamentally is capable of controlling motoring and generating."
    As far as I can see the FOC is only allowing me to change speed and torque of the motor.

    Unless, in order to run the motor as a generator, I simply need to rotate it in the direction opposite to the direction it is being driven?

    Is there a document detailing;
    How to correctly modify projects - I know how to link files to the project, but I feel I am missing something.
    I have watched many of your videos on BLDC motor control, and the intaSPIN-FOC methodology, I just don't know where to start.

    At this moment I am tinkering with project11b and the corresponding .c file- in a workspace created for this project.
    Am I along the right path?

    Cheers
  • 0 in reply to Morikeh Daramy
    TI__Guru** 119670 points
    I wouldn't say tinkering is a good path to be on, no.

    this article may help you some
    www.edn.com/.../Testing-your-motor-control-algorithms