Week 03
Current Loops
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
Treating back EMF as a slower disturbance leaves the armature R-L circuit as the current plant. A high current-loop bandwidth makes torque command tracking fast, but current limit and sampling delay bound the achievable response.
Concept map
- Current plant
- Bandwidth
- Current limit
- Sampling
Technical anchor
The approximate voltage-to-current plant is G_i(s) = 1/(L_a s + R_a), with electrical time constant tau_e = L_a/R_a.
How I review it
Keep target crossover below switching and sampling frequencies, then check peak current against the limit for a torque step and account for phase-margin loss from the sensor filter.
Connection to the full course
Unit 3 of 12. Unit numbers follow the control structure in the saved design files and do not claim attendance weeks.