STUPIDSID
Justify
1 (a) (i)
C.T secondary should never be kept open in any circumstances.
2 M
1 (a) (ii)
DC Series motor should never be started without mechanical load
2 M
1 (a) (ii)
Pole shoe section of DC machine is made larger than its body.
2 M
1 (b)
Explain each part of DC machine with neat sketch.
8 M
2 (a)
he Hopkinson's test on two shunt machines gave the following results for full load: Line Voltage=250V;Current taken from supply excluding field currents=50A; Motor
Armature current=380A; field currents 5A and 4.2A. Calculate the efficiency of the machine working as a generator. Armature resistance of each machine is 0.2 Ω.
7 M
Answer any one question from Q2 (b) & Q2 (c)
2 (b)
Define Pitch Factor and Distribution factor. Enlist advantages and disadvantages of short pitch or fractional pitch coil.
7 M
2 (c)
State methods to control speed of DC shunt motor. Explain any one method in brief
7 M
Answer any two question from Q3 (a), (b) & Q3 (c), (d)
3 (a)
Discuss essential and desirable conditions to be satisfied for parallel operation of two single phase transformers.
7 M
3 (b)
What is the necessity of starter in DC motor? Explain three point starter with neat sketch.
7 M
3 (c)
Write a short note on On load tap changer.
7 M
3 (d)
A shunt generator delivers 195A at terminal voltage of 250V.The armature resistance and shunt field resistance are 0.02 Ω and 50 Ω respectively. The iron and friction losses equal 950W. Find:
(i) Emf generated (ii) Cu losses
(iii) Output of the prime mover
(iv) Commercial, Mechanical and Electrical efficiencies
(i) Emf generated (ii) Cu losses
(iii) Output of the prime mover
(iv) Commercial, Mechanical and Electrical efficiencies
7 M
Answer any two question from Q4 (a), (b) & Q4 (c), (b)
4 (a)
Derive an expression for saving of copper when auto transformer is used compared to Two winding transformer.
7 M
4 (b)
Define armature reaction. Explain armature reaction effect in DC machine. How it can be minimized?
7 M
4 (c)
Draw and explain characteristics of DC series generator. Also enlist applications of DC series generator.
7 M
4 (d)
The following readings obtained from open and short circuit tests on 10KVA,400/100V,50HZ single phase transformer are:
O.C test: 100V,4A,80W on L.V. side
S.C. test: 10V,20A,120Won H.V. side
Compute:
(i) The equivalent circuit parameters referred to primary
(ii) Efficiency and voltage regulation at0.8 p.f lagging
O.C test: 100V,4A,80W on L.V. side
S.C. test: 10V,20A,120Won H.V. side
Compute:
(i) The equivalent circuit parameters referred to primary
(ii) Efficiency and voltage regulation at0.8 p.f lagging
7 M
Answer any two question from Q5(a), (b) & Q5 (c), (d)
5 (a)
Draw connection diagram and vector diagram for following connections of 3-Phase transformer.
(i) Dd6
(ii) Dy1
(iii) Yz11
(iv) Dd0
(i) Dd6
(ii) Dy1
(iii) Yz11
(iv) Dd0
8 M
5 (b)
A Δ-Δ bank consisting of three 20 KVA, 2300/230V transformers supplies a load of 40KVA. If one transformer is removed, find for the resulting V-V connection.
(i) KVA load carried by each transformer
(ii) Percent of rated load carried by each transformer
(iii) Total KVA rating of the V-V bank
(iv) Ratio of the V-V bank to ?-? bank transformer ratings.
(v) Percent increase in load on each transformer when bank is converted into V-V bank.
(i) KVA load carried by each transformer
(ii) Percent of rated load carried by each transformer
(iii) Total KVA rating of the V-V bank
(iv) Ratio of the V-V bank to ?-? bank transformer ratings.
(v) Percent increase in load on each transformer when bank is converted into V-V bank.
6 M
5 (c)
Explain direct load test on single phase transformer with circuit diagram.
7 M
5 (d)
Explain Scott connection in brief.
7 M
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