DRV8881: how to calculate power consumption of step motor and driver IC?

Yi,

1. There is no simple answer for the power consumption of stepper motors. From the motor design point of view, the power consumption includes iron loss and copper loss (https://www.geckodrive.com/support/step-motor-basics.html ). If we don't go that complicate route, the motor power consumption is equal to the motor driver output power minus the motor output mechanical power. The motor driver output is an AC output. The power P is equal to |S|*cosȹ (https://en.wikipedia.org/wiki/AC_power ).

2. The motor driver power dissipation calculation example can be found in DRV8889-Q1 datasheet https://www.ti.com/lit/ds/symlink/drv8889-q1.pdf

Hi Wang  Li

thanks for help.

I would like to ask another question. I think in order to form a sin/cos CURRENT curve in motor coils, the output volatge wave on DRV8889's H-Bridge( pin A/B_OUT1/2) should be like a sine-modulated wave , one example is as below. Is this understanding correct?  Thanks!

Yi,

If the motor doesn't move (without back EMF), the output voltage wave on DRV8889's H-Bridge( pin A/B_OUT1/2) should be like a sine-modulated wave as your example.

If the motor spins, the back EMF could cause the phase shift between the average voltage and current. Please check DRV8889 datasheet " 7.3.11.5 Stall Detection" section.