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DRV11873 Motor stops at 50% of the maximum frequency

Helmut Iser
Other Parts Discussed in Thread: DRV11873, DRV10983, DRV10975

When I slowly increase the speed of my 8-pole motor, the driver stops and restarts at exact 484 Hz. When I increase the speed faster, and the motor skips the critical speed, the driver is able to go up to about 960 Hz. It seems there is a problem only at 50% of the maximum speed.

I control the speed using a variable VCC, PWMin is HI, FS is HI (FastSpeed). There is no difference when I control the speed with PWMin or VCC.

The motor starts without problems and is able to run up to the maximum speed with only one exception - 50%.

If needed, I can provide several oscillograms. I am afraid there is a problem in the internal logic.

Is there any possibility to drive the motor with a variable speed without the risc the motor will stop and restart?

Thanks

Helmut

  • 0
    TI__Guru** 114905 points
    Hi Helmut,

    Our experts have been contacts and should reply soon.
  • 0 in reply to Rick Duncan
    TI__Expert 3010 points

    Hi Helmut,

    What is frequency of FG output ? We have encounter similar issue with similar lower voltage device www.ti.com/.../slva612.pdf

    This kind of issue happens only at one particular frequency, so work around as you have already experienced is to avoid operation at 50%

    I don't think there will be any problem operating this device at variable speed

    Regards,

    Krushal  

  • 0 in reply to Krushal
    Hi Krushal,

    Thank you very much for your reply. The application note SLVA612 explains exactly my problem. My critical FG frequency is 484Hz and 968Hz. The 305 samples condition explains why the motor can run at a higher speed when I increase the speed faster.

    Unfortunately we need the driver for a battery powered respiratory unit. The speed of the motor driving a fan depends on the selected airflow rate and the load. The load is variable at the filter side (particle filters, chemical filters) and /or at the head-peace (hood, gasmask, etc.). I can modify the software to avoid some critical frequencies, but the load can change unexpected (bending of the hose) and the motor speed can easily fall into the false-lock condition. A unwanted restart of a respiratory unit is very bad.

    The DRV11873 would be the ideal driver for our application. A very important feature is the ability to "catch" a running motor. Most of other drivers do have problems with it. We experimented with Agilent’s A4941. This driver can start only an almost stalled motor. There is no possibility do brake the motor electronically. Similar problems have drivers from Toshiba.

    I am very sorry about the false-lock problem of the TI drivers. It degrades this peace a lot.

    Once again, I thank you very much for the link. I'll do my best to overcome the issue and hope I can use the DRV11873 in our new product.

    Best regards
    Helmut
  • 0 in reply to Helmut Iser
    TI__Expert 3010 points

    Hi Helmut,

    Thanks for sharing the information. We have couple of more device from integrated FETs family DRV10983 and DRv10975. These devices doesn't have same problem as DRV11873. 

    DRV10983/75 also has many configuration options and are much more flexible

    Regards,

    Krushal  

  • 0 in reply to Krushal

    Hi Krushal,

    Thanks for the info and link to alternative devices.

    DVR10975 is not available in Europe. Its parameters would be okay except the RDSON. 1Ohm Resistance is too high.

    I will test the DRV10983. The parameters are acceptable. Its footprint (package) is slightly bigger, but I can deal with it. The only drawback is double the price compared to DRV11873.

    When I'm finished with my tests, I'll let you know.

    Best regards,

    Helmut

  • 0 in reply to Helmut Iser
    TI__Expert 3010 points
    Hi Helmut,

    Please contact local sales representative to discuss pricing . Let me know if you need any assistance in setting parameters for DRV10983

    Regards,
    Krushal
  • 0 in reply to Helmut Iser
    TI__Prodigy 575 points

    Hi Helmut,

    What issues did you face with the DRV10975 when you said "DRV10975 is not available in Europe"?