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Posted Date: 20 Oct 2007 Posted By:: Rajasekaran Member Level: Silver Points: 5 (Rs. 1)
2006 Anna University Chennai B.E Electronics & Tele-Communication Engineering EE1211-ELECTRICAL MACHINES Question paper
BE/B.TECH DEGREE EXAMINATION, NOVEMBER/DECEMBER 2006
Electronics and Communication Engineering
(Common to Electronics and Instrumentation Engineering and Instrumentation and Control Engineering)
Time:3Hrs Maximum:100 marks
Answer ALL questions.
PART A-(10X2=20 marks)
1.List the main constituents of stator of DC machine.
2.Give the expression for speed of a DC motor.
3.Define a transformer.
4.What are turns ratio and transformation ratio of transformer?
5.How are frequency of rotor induced emf and supply frequency related in a polyphase induction motor?
6.Where are split phase motors used?
7.Which type of synchronous machine is used with hydraulic turbines?What is their operating speed range?
8.Name two types of stepper motor.
9.What is the sub transmission network?
10.Name few insulating materials used in cables.
PART B-(5X16=80 marks)
11.(a)(i)Derive the emf equation of DC machine. How can its direction be obtained?(8)
(ii)What are the features of swinburne's test?(8)
(b)(i)A shunt machine,connected to a 200V mains has an armature resistance of 0.15ohm and the field resistance is 100ohm. Find the ratio if its speed as a generator to its speed as a motor,the line current in each case being 75A.(8)
(ii)Explain the principle of operation of DC motor.(8)
12.(a)(i)The OC and SC tests on a 4kVA, 200/400V,50Hz single phase transformer gave the following results:
OC test on LV side: 200V,1A,100W SC test with LV side shorted:15V,10A,85W.
Determine the parameters of the equivalent circuit and draw the equivalent circuit referred to the LV side.(12)
(ii)Define voltage regulation. Draw the phasor diagram of lagging power factor and determine voltage regulation.(4)
(b)(i)Discuss about the working principle of a transformer.(8)
(ii)Draw the phasor diagram and explain the operation of practical transformer on-load.(8)
13.(a)(i)Explain the torque slip characteristics of 3 phase induction motor.(10)
(ii)A 3 phase induction motor is wound for 4 ples and is supplied from a 50Hz supply.Calculate the synchronous
speed, the pseed of the motor when the slip si 3% the rotor frequency.(6)
(b)Explain the various schemes adopted in starting of three phase induction motors.(16).
14.(a).Write notes on:
(b)A 3 phase 12 pole synchronous machine has a star connected full pitch winding with 108 slots and 12 conductors
per slot.The fluc per pole is 50mWb and sine distributed. The speed of rotation is 500 rpm. Find the frequecny,
phase emf and the ine emf.(16)
15.(a)(i)Draw the structure of Electric power system and name the parts clearly.(10)
(ii)Write about pin type insulators.(6)
(b)Describe in short the following.
(i)Radial distribution system.(8)
(ii)Pole mounted substation.(8)
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