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DRV8462EVM: Similar Motors show different performance

Part Number: DRV8462EVM
Other Parts Discussed in Thread: DRV8462, DRV8434, DRV8711

Using the DRV8462 to drive 2 Stepper Motors gives different performance values. As one Motor was able to run, the other does not run at all.

1) TI Evaluation Board DRV8462, Supply Voltage 48V, Supply Current 8A

2) Motor under Test Motor 2A: 23H2076-200 and Motor 4A: 23H2076-400

3) Break

Type

Current

Resistance

Inductance

Holding Torque

Rotor Inertia

Length

Mass

 

(A)

(Ω)

(mH)

(N·m)

(g·cm2)

(mm)

(g)

23H2076-400

4

0.6

2.4

2

480

76.5

1060

23H2076-200

2

2.4

9

2

480

76.5

1060

The Motor 4A with Full Scale Current 5A was able to turn with differnt speeds and torque:

Speed [rpm]

 Torque [Nm]

300

1.34

600

1.1

900

0.27

1200

0.28

1500

0.09

1800

0.25

2100

0.06

2400

0.06

2700

0.24

3000

0.2

3300

0

3600

0

The Motor 2A with Full Scale Current 2.83A (also differnt values tested) was able to turn only to a speed of 400rpm. Higher speed where not possible.

  • Hi Andreas,

    The similarities of the two motors may end with the mechanical specifications. But they are different electrically. Could you please send the scope captures of the current waveforms of the 2A motor at lower speeds when it spins as expected as well as at high speed when it fails to spin (stall)? Does the two motor datasheets have speed vs. torque plots? It will be helpful to compare those plots. Thanks.  

    Regards, Murugavel

  • I am assuming these tests were conducted with auto torque feature disabled, just standard microstepping was used. What was the microstepping setting? Thanks.

  • Hi Murugavel Yes, thats write. I tried different Step Mode: 1/4, 1/8, 1/16 and 1/32. best regards Andreas

  • Please find Torque Plot for the 23H2076 Motor DINGS - Precision Motion Specialist (dingsmotion.com)

  • Hi Murugavel
    Please let me know with which motor coil Resistance / Inductance the DRV8462 will achieve best results / have you achieved best results. Motor Sizes of interest 23, 24 and 34 see below link to dingsmotion.

  • Hi Andreas,

    The time constant of the motor will determine how fast the current through the coil inductance will rise for a certain applied voltage regardless of the driver used. Lower time constant motors will support higher RPM at comparatively lower supply voltages. Lower the winding resistance and inductance and lower time constant the better. We can validate this with the current waveform at the target RPM. So for the 2A motor if you increase the supply voltage to for example 60V it will be able to run at higher RPM than 400 RPM, still may not achieve the performance of the 4A motor. DRV8462 can support up to 70V operation. We have tried various NEMA17, 23 and 34 stepper motors. From the motor data you provided, both 23H2076 and 23H2065 have significantly higher torque at 1000 RPM (2x or higher) compared to the other two NEMA23 motors. Hence the performance difference at higher RPM, 2A motor stalling at 400 RPM because the torque generated was not enough to overcome the system inertia. I hope this helps.

    Regards, Murugavel

  • Hi Murugavel

     

    I am a colleague from Andreas. He is not in today so I am writing.

    Can you share the speed torque curve you measured and settings you made with the NEMA 23,24 and 34? Do you also have the data sheet for the motors? Which driver did you take?

     

    Thanks

     

    Regards Thomas

  • Hi Thomas,

    I do not have the measured speed torque curve saved unfortunately. Motors tested were as below.

    1. NEMA17 J-4218HB2401. Tested with DRV8434, 8434S, DRV8462 EVMs

    2. NEMA23 23HS8430, datasheet attached. Tested with DRV8711, DRV8462 EVMs

    two-phase-four-phase-hybrid-stepper-motor-23hs.pdf

    3. NEMA34 34HS31-5504S. Tested with DRV8462V EVM. Note this EVM is not released yet. It uses the DRV8462 in DDV package with an external heatsink,  Heatsink datasheet ATS-TI10P-519-C1-R3.pdf

    Regards, Murugavel