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00000EE409121904

Answer any two full questions, each carries 10 marks.
What is meant by specific electric and specific magnetic loading in a 60
machine? From first principles, obtain the expressions for specific magnetic
loading and specific electric loading.
A 350KW, 500۷, 450 rpm, 6 pole ‏عل‎ generator is to built with an armature
diameter of 0.87m and core length of 0.32 m. The lap wound armature has 660
conductors. Calculate the specific electric and specific magnetic loadings.
A 50069, 460V, 8 pole, 375 rpm compound generator has an armature
diameter of 1.1m and core length of 0.33m. Design a symmetrical armature
winding. The armature ampere conductors/metre are 34000.The internal voltage
drop is 4% of terminal voltage and field current is 1% of output current. The
ratio of pole arc to pole pitch is 0.7.The voltage between adjacent segments at no
load should not exceed 159 and the slot loading should not exceed 1500 amps.
The diameter of the commutator is 0.65 of armature diameter and minimum
allowable pitch of segment is 4mm. Make suitable assumptions.
Derive the output equation of a synchronous generator

Find the main dimensions of a 2500 KVA, 187.5 rpm,50 Hz 3 phase 3 KV
salient pole synchronous generator. The generator is to be a vertical water wheel
type. The specific magnetic loading 15 0.6Wb/m”. The specific electric loading is
34000 Amp/m. Use circular poles with ratio of core length to pole pitch is 0.65.
Specify the type of pole construction used. The runaway speed is about 2 times
the normal speed.
PART D

Answer any two full questions, each carries 10 marks.
Explain the procedure for design of rotor bars and slots in a squirrel cage
induction motor.
Describe the salient features of computer aided design of electrical machines.
What are the advantages of computer aided design?
Derive an expression for the end ring current of a squirrel cage induction motor.

Explain how FEM is used for the analysis of electrical machines.

A 15689, 440V, 4 poles, 50112, 3 Phase induction motor is built with a stator
bore 0.25m and core length of 0.16m. The specific loading is 23000Amp
conductors/m. Using the data of this machine; determine the core dimensions,
no. of stator slots and number of stator conductors for a 11 KW, 460V, 6 pole,
50Hz motor. Assume a full load efficiency of 84% and power factor of 0.82 for

each machine. The winding factor is 0.955.

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