I've implemeneted a 3rd harmonic injection SVPWM (Space Vector PWM) scheme and it performs quite well. One peculiarity i have noticed was, when i set the modulation index to 0, the motor stops as expected but after leaving it like that for a couple minutes the H-bridges (Infinieon IFX007T) on my custom 3 phase inverter board got quite hot - okay to touch but still you wouldnt want to keep your finger on it for too long..
The modulation index at 0 corresponds to all 3 PWM duty cycles being at half the max value. In essence that should be "zero power transfer" but the H-bridges getting hot clearly indicates a power transfer and considering you can measure the current at this state ( when the motor is running ) got me wondering.
A quick "hack" would be just manually setting the duty cycles to 0 or shutting down the inverter entirely but i would like to know the inner workings behind it and if thats normal behavior.
TLDR; Setting modulation index to 0 returns duty cycles that are half the max duty cycle. Would it be ok to leave the motor like this for hours or would it still drain some power ?