Question
Download Solution PDFThe effective resistance of a 2200 V, 50 Hz, 440 KVA, single-phase alternator is 0.5 Ω. On short circuit, a field current of 40 A gives the full load current of 200 A. The electromotive force on open circuit with same field excitation is 1160 V. Calculate the synchronous impedance.
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFThe correct answer is option 2):(5.8 Ω)
Concept:
Finding Synchronous Impedance (Zs) with the help of OCC and SCC:
Synchronous impedance is the ratio of Open circuit voltage per phase to the short circuit armature current at the same value of field current (Excitation).
Let the rated field current is IA, and we have to find the Open circuit voltage and short circuit armature current at this value by plotting the graph as shown,
From the above characteristics, At rated field current (IA),
Open Circuit Voltage (VOC) = OB
Short Circuit Current (ISC) = OC
Synchronous Impedance (Zs) = \(OB\over OC \)Ω
From using the concept of, Z2 = R2 + X2,
we easily find the Synchronous reactance. And
Armature resistance will find by using the Voltage Test Method or (VA or AV) method.
Calculation:
Given
Ra = 0.5 Ω
field current = 40 A
ISC = 200 A
VOC = 1160 V
Hence, ZS = \(V_{oc}\over I_{SC}\)
=\(1160 \over 200\)
= 5.8 Ω
Last updated on May 29, 2025
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