GATE EE 2014 Set 1 — Question 23
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Electrical Machines → Synchronous Machines → Synchronous Reactance & Regulation
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Question
A star connected 400 V, 50 Hz, 4 pole synchronous machine gave the following open circuit and short circuit test results:
Open circuit test: V (rms, line-to-line) at field current, A
Short circuit test: A (rms, phase) at field current, A
The value of per phase synchronous impedance in at rated voltage is __________.
Open circuit test: V (rms, line-to-line) at field current, A
Short circuit test: A (rms, phase) at field current, A
The value of per phase synchronous impedance in at rated voltage is __________.
Correct answer
14.5 to 15.5
Solution
Given:
Rated line voltage V
Rated phase voltage V
From Open Circuit (OC) test: V at A.
From Short Circuit (SC) test: A at A.
Assuming the magnetic circuit is linear (air-gap line), the short-circuit current at the rated field current ( A) is calculated as:
A
The synchronous impedance at rated voltage is:
The official range is 14.5 to 15.5.
Rated line voltage V
Rated phase voltage V
From Open Circuit (OC) test: V at A.
From Short Circuit (SC) test: A at A.
Assuming the magnetic circuit is linear (air-gap line), the short-circuit current at the rated field current ( A) is calculated as:
A
The synchronous impedance at rated voltage is:
The official range is 14.5 to 15.5.
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