Download PTU B-Tech EEE 2020 Dec 4th Sem 72385 Electrical Machinery Ii Question Paper

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Roll No. [] [] Total No. of Pages : 02

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Total No. of Questions : 18

B.Tech.(Electrical & Electronics Engg.) (2013 Onwards)/

B.Tech.(Electronics & Electrical Engg.) (2013 & Onwards)

(Sem.-4)

ELECTRICAL MACHINERY-II

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Subject Code : BTEEE-401

M.Code : 72385

Time : 3 Hrs. Max. Marks : 60

INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.

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2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

SECTION-A

Answer briefly :

1. What are the advantages of cage type induction motor?

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2. State the advantage of using capacitor start motor over a resistance split phase motor.
3. What is the necessity of computing voltage regulation of synchronous generator?
4. What are the various methods available for making single phase motor self starting?
5. Define distribution factor of the winding of the synchronous generator.
6. What are the different methods of finding out the voltage regulation of an alternator?

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7. An alternator is used as synchronous condenser; under what conditions it should operate.
8. What is V curve of synchronous motor?
9. State the necessity of parallel operation of two alternators.
10. What is shaded pole motor?

SECTION-B

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1. Draw the equivalent circuit and phasor diagram to find out the Emf generated in synchronous generator for lagging power factor.
2. Explain the working principle of hysteresis motor.
3. Explain V curve and inverted V curve of synchronous motor with neat diagram.
4. A 3 phase induction motor runs at almost 1000 rpm at no load and 950 rpm at full load when supplied with power from a 50 Hz 3 phase line
   1. How many poles have the motor?
   2. What is the % slip at full load?

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   3. What is the corresponding frequency of rotor voltages?
   4. What is the corresponding speed of rotor field with respect to rotor?
   5. What is the corresponding speed of the rotor with respect to stator?
5. Explain the synchronoscope method for synchronising two alternators. Also give the conditions for synchronising the alternators.

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SECTION-C

1. A cage induction motor when started by means of a star-delta starter takes 180% of full-load line current and develops 35% of full-load torque at starting. Calculate the starting torque and current in terms of full-load values, if an auto-transformer with 75% tapping were employed.
2. The power input to a 6-pole, 50Hz 3-phase induction motor is 700W at no-load and 10kW at full load. The no load copper-losses may be assumed negligible, while the full load stator and rotor copper losses are 295 W and 310 W respectively. Find the full load speed, shaft torque and efficiency of the motor assuming rotational and core losses to be equal.
3. Explain the armature reaction in synchronous generator for :
   1. Unity power factor,
   2. Lagging power factor,

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   3. Leading power factor.

NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any page of Answer Sheet will lead to UMC against the Student.

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