STUPIDSID
1 (a)
Deduce the expression of M.M.F. for the air gap of the armature for the slotting and ducting.
7 M
1 (b)
Explain the factors affecting the choice of electrical loading.
7 M
2 (a)
Explain the Real and Apparent flux densities.
7 M
Answer any two question from Q2 (b) or Q2 (c)
2 (b)
Derive the expression for the leakage permeance of parallel sided slot.
7 M
2 (c)
Show that for minimum total material cost of a 3-phase transformer the ratio (Weight of iron/Weight of copper) should be equal to the ratio (specific cost of Copper (Rs./kg) / specific cost of iron ((Rs./kg)).
7 M
Answer any two question from Q3 (a), (b) or Q3 (c), (d)
3 (a)
Define specific magnetic loading (Bav) and specific electric loading (ac) and obtain an expression for the output co-efficient for a D.C. machine.
7 M
3 (b)
Discuss the factors that determine the choice of air-gap in induction motor.
7 M
3 (c)
Deduce an expression for the design of core for Square and cruciform sections also state the reason why circular coils are always preferred in Comparison to rectangular coils.
7 M
3 (d)
Define heating time constant and explain how it can be evaluated from heating curve.
7 M
Answer any two question from Q4 (a), (b) or Q4 (c), (d)
4 (a)
Derive the expression for the KVA rating of a three phase transformer and show that the e.m.f per turn E =K√KVA.
7 M
4 (b)
Derive the condition for the optimum design of transformer for the minimum cost and minimum losses.
7 M
4 (c)
Explain the methods of estimation of motor rating for variable load drives.
7 M
4 (d)
The temperature rise of a transformer is 25° after one hour and 37.5° after two hours of starting from cold conditions. Calculate its final steady temperature rise and the heating time constant. If its temperature falls from the final steady value to 40°C in 1.5 hour when disconnected, calculate its cooling time constant. The ambient temperature is 30°C.
7 M
Answer any two question from Q5 (a), (b) or Q5 (c), (d)
5 (a)
What are the important considerations in choosing number of poles in D.C. machine?
7 M
5 (b)
List and explain briefly the limitations being imposed in the design of electrical machines also discuss the modern trends in the design.
7 M
5 (c)
What are the types of windings commonly used in transformer and on what basis are they selected?
7 M
5 (d)
Explain the methods for the estimation of Mmf for the tapered teeth.
7 M
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