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10000EE409122005

PART (^

Answer any two full questions, each carries 10 marks.
How can the main dimensions D and L can be separated for a DC machine?
Differentiate hydro generators and turboalternators
A design is required for ೩ 50kW,4 pole ,600 rpm DC shunt generator. The full
load terminal voltage being 220 V. If the maximum gap density is 0.83wb/m?
and the armature ampere conductors per meter are 30000.Calculate the pole
dimensions of the armature.The armature core is of square pole face.Assume
that full load armature voltage drop is 3% of the rated terminal voltage and
field current is 1% of rated full load current. Take ratio of pole arc to pole pitch
to be 0.67
A 600 MVA, 22000V, 50hz, 2 pole , 3 phase star connected direct water cooled
generator has a stator bore of 1.3 m and stator core length of 6m.The specific
electric loading is 200000 A/m and winding factor is 0.955.If the stator winding
has 2 conductors per slot and there are 2 circuits per phase, calculate
(1) Number of turns
(ii) Number of slots
(ii) Average flux density in the air gap

PART 0

Answer any two full questions, each carries 10 marks.
Explain the design of rotor bars in three phase induction motors
A I1kV, three phase, 6 pole, 50117, 220 V, star connected induction motor has
54 stator slots each containing 9 conductors. Calculate the value of rotor bar
current and area of rotor bars. The number of rotor bars is 64. The machine has
an efficiency of 0.86 and power factor of 0.85. Rotor mmf may be assumed as
85% of stator mmf. Assume a current density of 5 4 /mm?
A three phase, 2 pole, 50 Hz, squirrel cage induction motor has a rotor diameter
of 20 cm and core length of 12 cm.The peak density in the air gap is 0.55
wb/m2.The rotor has 33 bars ,each of resistance 125/0) and inductance of
2uH .The slip is 6%.Calculate the peak value of current in each bars.
Explain the different types of CAD software used
Write short notes on (i) Advantages of FEM (ii) New computer aided machine

software using Finite Element (iii) Hybrid method (iv) Applications of FEM

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