Week 05
Open- and Short-Circuit Tests
I revisit magnetic circuits, transformers, and rotating machines around my transformer report and calculation sheets.
What I connect in this unit
The open-circuit test mainly exposes core loss and the magnetizing branch at low current, while the short-circuit test applies low voltage to circulate rated current and extract winding resistance and leakage reactance. Instrument error and temperature propagate into parameter-extraction uncertainty.
Concept map
- Open-circuit test
- Short-circuit test
- Parameter extraction
- Measurement error
Technical anchor
From open circuit, use R_c = V_oc^2/P_oc, I_w = P_oc/V_oc, and X_m = V_oc/sqrt(I_oc^2-I_w^2); from short circuit, use Z_eq = V_sc/I_sc and R_eq = P_sc/I_sc^2.
How I review it
Record meter ranges, reference winding, and whether values are per phase or three phase; then check that X_eq = sqrt(Z_eq^2-R_eq^2) is real and whether resistance needs temperature correction.
Connection to the full course
Unit 5 of 12. Unit numbers expand the saved report and calculations into a reading sequence rather than an attendance record.