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Department of Electrical Engineering

This document contains 5 questions for a unit test on electrical engineering. Question 1 asks to calculate the full-load regulation of a 3-phase alternator given its short-circuit current, open-circuit voltage, and armature resistance. Question 2 provides open-circuit test data for a 3-phase alternator and asks to determine its short-circuit characteristic and field excitation/regulation at full load. Question 3 asks about the meaning and significance of short-circuit ratio for an alternator. Question 4 describes two self-start methods for synchronous motors or compares regulation calculation methods for alternators. Question 5 discusses features of 3-phase synchronous motors or explains the dark lamp method for synchronizing alternators.

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100 views1 page

Department of Electrical Engineering

This document contains 5 questions for a unit test on electrical engineering. Question 1 asks to calculate the full-load regulation of a 3-phase alternator given its short-circuit current, open-circuit voltage, and armature resistance. Question 2 provides open-circuit test data for a 3-phase alternator and asks to determine its short-circuit characteristic and field excitation/regulation at full load. Question 3 asks about the meaning and significance of short-circuit ratio for an alternator. Question 4 describes two self-start methods for synchronous motors or compares regulation calculation methods for alternators. Question 5 discusses features of 3-phase synchronous motors or explains the dark lamp method for synchronizing alternators.

Uploaded by

sahebrao
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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Department of Electrical Engineering

MARK-30 UNIT TEST 05 DATE 10.11.2020

Q1. A three-phase, star-connected, 1000 kVA, 3300 V, 50 Hz alternator produces a short-


circuit current of 200A and an open circuit voltage of 1040 V with the same field current 40
A. It its armature has an effective resistance of 0.2 ohm per phase, calculate full-load
regulation of the alternator at a pf of 0.8 lagging and 0.8 leading. 6M
Q2. The open-circuit test data of a 500 kVA, 4000 volt, 8 pole, 3-phase, 50 Hz alternator is:
ATs, per pole 2000 3000 3560 5000 6200 7000 8000
Terminal voltage 1990 2900 3400 4000 4400 4590 4800
The equivalent armature reaction expressed in ampere-turn per pole is 1.1 × ampere
conductors per pole per phase. There are 240 conductors per phase in series. If the inductive
voltage drop 8% on full load and the resistance drop is negligible. Then determine (i) Short
circuit characteristic (ii) field excitation and regulation for full load at 0-8 p. f. lagging 8M
Q3. What is meant by short circuit ratio in case of alternator? Elaborate its significance. 4M
OR
Q3. Compare three phase induction motor with three phase synchronous induction motor. 4M

Q4. Describe any two methods of making the synchronous motor self start? 6M
OR
Q4. Compare - Direct method, emf method, MMF method of finding regulation of alternator. 6M

Q5. State three important features possessed by 3 phase synchronous motor. What do you mean
by ‘V’ curves and Inverted ‘V’ curves of synchronous motor. 6M.
OR
Q5. Explain the dark lamp method used for synchronizing of alternators. 6M

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