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Brushless DC Driver for slow speed.

Gabriel Ecker
Prodigy 90 points
Other Parts Discussed in Thread: DRV10970, DRV8306EVM

Hello,

I'm looking for a BLDC contoller/driver for my sensored motor which is able to drive my motor at slow speed (approx 150 rmp) with high torque/current.

My motors datasheet is available at: https://de.nanotec.com/fileadmin/files/Datenblaetter/BLDC/DF45/DF45M024053-A2.pdf

Opperation voltage is about 15V.

I have tryed to do this with a DRV10970, but at these slow speed the torque is to less.

Has somebody experice with contoller for slow speed?

Thanks!

Regards

Gabriel

  • 0
    TI__Expert 6065 points
    You can estimate Imax = (Vcc- Kt*SpeedHz)/RphaseToPhase. So if Vcc = 15V and Kt = 0.0335 Nm/A = 0.0335 V/Hz, and RphaseToPhase = 0.8ohms, and ElecFreqSpeedHz = 150Targetrpm*8polePairs/60 = 20Hz, then max current = (15V - 0.0335 V/Hz*20Hz)/0.8 ohms = 17A. Im surpried that the DRV10970 is not driving more current at 150 rpm assuming you are doing 100% duty cycle on pwm pin.

    1) what is the motor phase current being drawn at the target speed of 150rpm for DRV10970? If possible, getting a scope capture of the motor phase current would be useful. Also make sure there is no extra motor line resistance that causes the current to decrease.
    2) For sensored Hall motor drivers at low speeds, I believe any hall driver should be able to do it, but I will check with my coworkers. You can also look through the sensored BLDC drivers through this link ( www.ti.com/.../products.html )
  • 0 in reply to Sanmesh Udhayakumar
    Prodigy 90 points

    Thank you for your answer!

    With the evaluation board it is possible to go up tp 95% duty cyle. But it seems it doesn't realy matter, when I start the motor an let it run at slow speed and than start to load it by breaking it with one hand a rise in duty cycle doesn't affect anything.

    1) I will try to get a scope capture of the phase current on monday, currently I just monitored the current from the 15V source. Maybe the Rds(on) from DRV10970 with 400mOhms could be a problem. There are no extra resistances in the curcuit.

    2) I already looked for the BLDC drivers, because of space reasons I decided for the DRV10970 with integreated FETs.

    Regards

    Gabriel

  • 0 in reply to Gabriel Ecker
    Prodigy 90 points

    I uploaded the scope captures in the other forum: https://e2e.ti.com/support/motor-drivers/f/38/p/801894/2971216#2971216

    Maybe I just need a drive for higher current?

    Regards

  • 0 in reply to Gabriel Ecker
    Prodigy 90 points
    I have got an DRV8306EVM now it works fine.

    Thank you!