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“It is the mark of an educated mind to be able to entertain a thought without accepting it.”

DEPARTMENT OF EI

ELECTRICAL MACHINE ASSIGNMENT 1

1. Explain the Basic concepts of rotating machine.

2. With help of proper block diagram explain the working of Generator.

3. Explain Faraday’s Law of Electromagnetic induction. Explain it in context of Generator.

4. Explain the working principle of D C Motor.

5. Explain the electrical and mechanical parts of Electrical Machine.

6. Explain the interaction of two magnetic fields 7. Explain in detail the armature reaction in the DC machines. 8. Draw and explain the equivalent circuits of transformer 9. Discuss the basic concept of emf generation in a DC machine in detail.

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ASSIGNMENT 2

1. Explain the construction of D C Machine with proper diagram.

2. The armature of an 8 pole generator has 220 slots, each slot carry 20 conductors. The armature winding is wave wound and flux developed by each pole is 0.04 Wb. The generator is driven at 2000 rpm. Calculate emf induced in the generator

3. What is Back EMF? Explain its significance in DC machine.

4. Explain the armature reaction and its effect on the operation of DC Machine. What are the methods used for removing its disadvantages?

5. Derive the Power Equation and Torque Equation of a DC Motor.

6. What is commutator.Explain the commutator action.

7. Explain the characteristics curves of

i) DC shunt motor

ii) DC series motor

iii) DC compound motor

8. What are the speed control methods for a DC motor and explain flux control method for speed control.

9. Explain the starting method of a DC motor and explain 3 point starter and 4 point starter.

10. A four-pole, 220 V, lap-connected DC series motor has 200 slots with six conductors per slot. The current is 40 A and flux/pole is 16 mWb. The armature and field resistances are 0.46 Ω and 0.26 Ω, respectively. The iron and friction losses are 700 W. Calculate the useful torque.

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ASSIGNMENT 3

1. Derive the emf equation for a synchronous machine.

2. Explain the winding factor, coil span factor and distribution factor.

3. Explain the armature reaction for a synchronous machine.

4. What do you mean by synchronous reactance and synchronous impedance?

5. Describe the regulation of an alternator by using synchronous impedance method.

6. What do you understand by synchronizing of the alternator?

7. Explain the construction and operating principle of synchronous machine.

8. What are starting methods of a synchronous motor?

9. Explain the V curves and the inverted V curves.

10. A three-phase, star-connected, 6,600 V synchronous motor has a synchronous reactance per phase of 15O. For a certain load, the input is 900 kW at normal voltage and the induced line emf is 8,900 V Neglecting armature resistance, determine the following:

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ASSIGNMENT 4 1. Explain the construction and working of a three phase induction motor.

2. Explain the concept of rotating magnetic field in three phase induction motor.

3. Write the note on

i) Synchronous speed

ii) Slip

iii) Rotor Reactance and rotor current

4. Derive the torque equation of induction motor and explain the full load torque, starting torque and the condition of maximum torque.

5. Explain the torque slip characteristics of induction motor and describe the significance of stable and unstable region.

6. What is the effect of change in rotor resistance on a torque developed in a rotor?

7. What is the need of starter for induction motor? Explain the types of starter.

8. Explain the rotor resistance starter with proper diagram.

9. Describe the methods for the speed control of a three phase induction motor.

10 A 1,100 V, 50 Hz delta connected induction motor has a star-connected slip-ring rotor with a phase transformation ratio of 3.8. The rotor resistance and standstill leakage reactance are 0.012 Ω and 0.25 Ω per phase, respectively. Neglecting stator impedance and magnetizing current, determine the following:

(i) The rotor current at start with slip ring shorted.

(ii) The rotor power factor at start with slip ring shorted.

(iii) The rotor current at 4 per cent slip with slip ring shorted.

(iv) The rotor power factor at 4 per cent slip with slip ring shorted.

(v) The external rotor resistance per phase required to obtain a starting current of 100 A in the stator supply lines.

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ASSIGNMENT 5

1. Explain the construction and working of a single phase induction motor.

2. Describe the starting methods of single phase induction motor.

3. Explain the construction and working of a single phase synchronous motor.

4. Explain the construction and working of a stepper motor.

5. What is the difference between squirrel cage and wound rotor.

6. What is the difference between Salient pole type rotor and smooth cylindrical type rotor?

7. Explain the characteristics of stepper motor.