Week 08
PWM and Current Ripple
I use my PSIM report and PI calculation file to revisit the DC-motor model, cascaded current-speed loops, and field weakening.
What I connect in this unit
Raising switching frequency reduces current ripple for the same inductance but increases switching loss. Timer duty resolution limits small voltage commands, and dead time prevents shoot-through while introducing current-direction-dependent average-voltage error and low-speed torque ripple.
Concept map
- Switching frequency
- Duty resolution
- Current ripple
- Dead time
Technical anchor
Current change over one PWM interval is approximately Delta i = (v_applied - E_back) Delta t/L_a, while timer-count range sets the available duty step Delta D.
How I review it
Estimate ripple at maximum speed and stall, apply minimum pulse width, dead time, and timer resolution, and then check whether the usable duty range can represent the required voltage.
Connection to the full course
Unit 8 of 12. Unit numbers follow the control structure in the saved design files and do not claim attendance weeks.