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Current waveform with two different Stepper Motors

Jenifer Blanco
Prodigy 60 points
Part Number: DRV8424EVM

Hi, 

I have a question related with the current regulation. 

This is my actual driver configuration: 

  • 1/16 Microsteps
  • Smart tune dynamic decay and Smart tune ripple control (both have been tested)
  • Toff = 16us
  • Running Current = 800mA
  • Speed = 300rpm

I have used two different  stepper Motors: 

  • 29QQ Peristaltic Pump from Boxer pumps (200 steps per rev)
  • Minebea 17PM-K443BNVA1637 (200 steps per rev)

I have measured the current with this configuration using a Shunt (2A-200mV), and the current has the following waveform for the 29QQ Stepper Motor without load: 

With the same configuration using the Minebea 17PM stepper motor with a small load, the current waveform is the following: 

In the second motor is possible to appreciate that the current has no sinusoidal waveform. Why is this happening?. I have read in the following document https://www.tij.co.jp/jp/lit/ml/slyp742/slyp742.pdf?ts=1644397542933&ref_url=https%253A%252F%252Fwww.google.com%252F that using the Smart ripple control  the driver maintains sinusoidal current waveform at any speed. But I don´t see that in my measurements with the second motor. 

Please could you give me an explanation why the sinusoidal current waveform is not maintained?

Thank you very much in advance

Best Regards

  • +1
    Genius 3580 points

    Hi Jenifer,

    The second current waveform is affected by motor BEMF which is close to driver VM at that speed. If you want to get sinusoidal current with that motor you can do the following:

    - increase VM voltage if driver can work with higher voltage

    - choose the motor from the same family but with lower windings inductance and higher current (and lower BEMF for the same speed)

    - sometimes stepper motors have 8 leads that allows to operate them in parallel or in series then go for parallel connection which gives lower impedance and lower BEMF

    - reduce motor speed.

    Regards,

    Grzegorz

  • 0 in reply to Grzegorz Pelikan
    Prodigy 60 points

    Hi Grzegorz, 

    thank you very much for your fast response, I will take all these points into account. 

    Thanks again

    Best Regards

    Jenifer