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G192102 Pages:2

Examine the factors that influence the choice of flux density of a transformer.
PART C
Answer any two full questions, each carries 10 marks.
Differentiate between square pole face and rectangular pole face.
A 4 pole 25hp, 500 V,600 rpm DC series motor has an efficiency of 82%.The
pole faces are square and the ratio of pole arc to pole pitch is 0.67, Bay=0.55
पः, ac=17000A/m. Obtain the main dimensions, number of slots, and conductors
per slot. Assume it to be wave winding.
List the factors to be considered for the choice of specific electric loading in
synchronous machines.
A 3 phase 1800 kVA, 3.3 kV, 50 Hz, 250 rpm, salient pole alternator has the
following design data. (i) Stator bore diameter = 230 cm (ii) Gross length of
stator bore ಎ 38 cm, (iii)Number of stator slots = 216, (iv)Number of conductors
per slot = 4 (v) Sectional area of stator conductor = 86 mm’, Using the above
data, calculate (i) Flux per pole (ii) Flux density in the air gap (iii) Current
density (iv) Size of stator slot.
What are the advantages and disadvantages of higher number of poles in dc
machine?
Explain any 3 methods of cooling for turbo alternators.
PART D
Answer any two full questions, each carries 10 marks.
Estimate the stator core dimensions, number of stator slots and number of stator
conductors per slot for a 100 kW, 3300 V, 50 Hz, 12 pole, star connected slip
ring induction motor. Assume, Average gap density=0.4 Wb/m’, ampere
conductors per metre = 25,000 A/m, Efficiency = 90%, Power factor = 0.9 and
winding factor = 0.96. Choose main dimensions to give best power factor. The
slot loading should not exceed 500 Ampere conductors.
Explain on synthesis method of solving electrical machine using CAD with a
flow chart.
What are the advantages of hybrid methods?
Explain how finite element method is used for analysis of electrical machines.
Derive from first principles, the output equation of a 3-phase induction motor.

Explain each term used.

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