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Parametric search for a basic application : RMS current measure

A GIR
Genius 3615 points
Other Parts Discussed in Thread: TMS320F28015, C2000WARE, TMS320F280041

Hello

We currently working on a board to control a Brushless motor. Then we used the F28377s (Issued from the ControlCard and IDDK kit)

So we use CCS with the CMWare, we have some tool like the debugger Blackhawk.

For another need, I'm looking for the good Cpu:

We need to measure the Rms currrent consumed by a asynchrones tree-phase motor . (We can't know the motor angle position)

Then this motor is driven by a controller which make change the voltage and the frequency of the tree phase signal.

We must be plug between the controller and the motor to measure the current in the motor phase (I think we need measure only 2 phases..?)

The Idea is to measure the current via an ADC with a LEM into two phase and then deduce the Rms current.

Then by parametric search, I found the basic µC TMS320F28015.

But this device is not supported by the CMWare2000 :-(

So, my question is:

In your opinion, which smallest CPU could I use to measure the Rms current in an asynchrones tree-phase motor?

Is there some existing application notes? schematic? evaluation board? software? exemple?.....

Thank for your reply.

  • 0
    TI__Guru 57255 points

    Hi,

    Is there a reason that you wouldn't want to tie the motor phase current signals to the F28377D that you're already using for controlling the inverter?  If you do this, you might even be able to take the approach taken on the IDDK, where isolated delta-sigma modulators & the C2000 demodulator is used.

    If the main goal for the new microcontroller (& you need a second MCU) is to measure this phase current, than an MSP430 may be the cheapest route.  From the C2000 family, the F280200 would probably be most appropriate - but even then I'd recommend trying to do other tasks with an F280200 device, if you put it in.


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Genius 3615 points

    Hello

    The main reason why we won't change the µC is the cost of it!.

    Te F28377 is about $10-$15 and take many place on the board.

    The F2801x is less than $4

    The F2802x is about $8-$10 it seems.

    So the F28377 is a big chip for the need we have for this new project. We just need measure two phase current to determine the motor Rms current.

    I'm sure there are some exemple to do this but I'm not found.. :-(

    Also, for the cost reason, we think use LEM module instead of Sigma-Delta component.

  • 0 in reply to A GIR
    TI__Guru 57255 points

    Hi,

    Sorry, I don't think I fully comprehended that your current MCU need is for a new project.

    Even though you're seeing that the F2801x is cheaper than the F280200, I'm not sure that will be true across various volume numbers.  I suspect that the F2802x family will be cheaper, but will ask someone from marketing to comment.

    If that is really the scope of the project, then no matter which C2000 you use, you will be carrying around a lot of features inside the chip that won't really be helping you.  It would be better to choose a chip which better matches your simpler need - and only has fewer extra features for your project.  As above, I'd recommend something from the MSP430 line.  The ADC on these devices is optimized more around resolutions vs speed (for things like e-metering) - and will likely be good for your signals.  You might be able to get a more precise recommendation by asking that forum.

    Hopefully this helps!


    Thank you,
    Brett



  • 0 in reply to A GIR
    TI__Guru** 118000 points
    F2802x is our lowest end Piccolo series, it starts at $1.99 1ku
    www.ti.com/.../overview.html

    All of the Piccolo devices have generic C2000Ware device support
    For C2000Ware driverlib support you would need to look at the new F28004x Piccolo series, for example
    TMS320F280041

    I suspect you have confused F2802x pricing with the F282x series.
  • 0 in reply to ChrisClearman
    Genius 3615 points

    Ok,

    I will study this.

    The other constraint for us is to reduce the time to market to do it.

    We have less than 10 day to do it!

    Then more I reuse what I know on F28377 faster will be the develop time...

  • 0 in reply to A GIR
    TI__Guru** 118000 points

    Well, I won't comment on the feasibility of 10 days...

    If you need to reuse F28377 work, an F28075 would be the quickest....F280049 would also be straightforward.