1. SYNCHRONOUS MACHINES - Open circuit & Short circuit tests -
SEE 3433
MESIN ELEKTRIK
SYNCHRONOUS MACHINES - Open circuit & Short circuit tests -

2. These tests are conducted to determine the synchronous reactance of a synchronous machine
Conducted in SEE Electrical Machine Laboratory

3. Stator terminals open  Ia = 0  Vt = Ef
Open-circuit test
Open Circuit Characteristic (OCC)
Rotor runs at constant speed – field current adjusted  Ef depends only on flux per pole or If
Stator terminals open  Ia = 0  Vt = Ef
Air-gap line
Ef,
Modified air-gap line
Excitation voltage with no saturation
OCC
Vt,rated
Magnetic saturation If

4. No saturation since airgap flux is small
Short-circuit test
Short Circuit Characteristic (SCC)
Rotor runs at synchronous speed - stator terminals shorted – stator current plotted against If
No saturation since airgap flux is small
Ef, Ia
OCC
Vt,rated
SCC If

5. Determining Xs
OCC
Vt,rated
Ef, If Ia
SCC

6. Determining Xs If’’ If’ Synchronous reactance, Xs = Ia,rated Ia’ Ef,
OCC
Vt,rated
SCC
Ia,rated
If’’
Ia’ If
Synchronous reactance, Xs =