Question
Download Solution PDFA 400 V, 30 kVA, single-phase alternator has an effective armature resistance of 0.3 Ω. An excitation current of 20 A produces 266 A armature current on short-circuit and an EMF of 400 V on open-circuit. The synchronous impedance and synchronous reactance of the alternator are, respectively, ________.
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept
The synchronous impedance is calculated using the open-circuit voltage and the short-circuit current:
\(Z_s={V_{oc}\over I_{sc}}\) at the same field or excitation current
where, Voc = Open circuit voltage
Isc = Short circuit current
The synchronous reactance of the alternator is given by:
\(X_s=\sqrt{Z_s^2-R_a^2}\)
Xs = Synchronous Reactance
Zs = Synchronous impedance
Ra = Armature resistance
Calculation
Given, Voc = 400 V
Isc = 266 A
Ra = 0.3 Ω
\(Z_s={400\over 266}=1.504\space \Omega\)
\(X_s=\sqrt{1.504^2-0.3^2}\)
Xs = 1.46 Ω
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