JNTU B.Tech III ELECTRICAL MACHINES-III Previous Question Paper (August/September - 2024 - R13)

Define Pitch factor of a Synchronous Machine.

What are the differences between round rotor and salient pole rotor synchronous machines?

Give equation for regulation by synchronous impedance method and give its limitations.

What are the parameters to be considered for evaluating regulation of a salient pole alternator?

Define synchronization and give the conditions to be satisfied for parallel operation of alternators.

What is sub-transient reactance? Give its equation.

What is hunting in synchronous motors?

What is synchronous induction motor and give its applications?

Give the applications of split phase motors.

What are the advantages and disadvantages of capacitor start single phase induction motors?

Based on the construction describe various types of AC Generators give its applications also.

A 16 pole alternator has 144 slots. If the coil pitch is kept 5 slots, then calculate its pitch factor?

What is distribution factor and winding factor, derive the emf equation based on winding factor for AC generator?

Determine the frequency of a 8 pole alternator rotating at 375RPM. If the number of poles is doubled, then what will be its new frequency?

Explain the method of getting the regulation by using synchronous impedance method.

A 1500 KVA, 6600V 3 phase star connected alternator with a resistance of 0.4 ohms and reactance of 6 ohms per phase, delivers full load current at power factor 0.8 lagging, and normal rated voltage. Estimate the terminal voltage for the same excitation and load current at 0.8 power factor leading.

Briefly discuss about the regulation by mmf method and give its merits and demerits.

A 3 phase star connected alternator is rated at 1600KVA, 13500V. The armature effective resistance and synchronous reactance are 1.5 ohms and 30 ohms respectively per phase. Calculate the percentage regulation for a load of 1280kW at power factor of 0.8 leading?

List out the conditions to be fulfilled for running two generators in parallel? Describe any two methods of synchronizing two 3 phase alternators?

Two identical 3 phase star connected generators operating in parallel, share equally a total load of 750KW at 6000V and power factor 0.8. The synchronous reactance and resistance of each machine are respectively 50ohms and 2.5 ohms per phase. The field of the first generator is excited so that the armature current is 40A (lagging). Find i) armature current of second alternator, ii) power factor of each machine.

Discuss the effect of change of excitation and mechanical power input to an alternator.

Two synchronous generators are connected to bus-bars having a constant voltage of 10000∟00 V. Generator A has an induced emf of 13000∟22.60V and a reactance of 2 ohms; generator B has an emf of 12500∟36.90 V and a reactance of 3 ohms. Find the current, KW and KVAr supplied by each generator.

With the help of neat sketch, explain the working principle of synchronous motor.

A 400V, 6 pole, 3 phase, 50 Hz, star connected synchronous motor has a resistance and synchronous reactance of 0.5 ohm and 4 ohm per phase respectively. It takes a current of 20A at unity power factor when operating with a certain field current. If the load torque is increased until the line current is 60A, the field current remaining unchanged, find the gross torque developed, and the new power factor.

Write a short notes on locus power diagram of a synchronous machine as a circle? Give the coordinates of the power circle.

A 2000V, 3 phase star-connected synchronous motor has an effective resistance and synchronous reactance of 0.2 ohm and 2.2 ohm per phase respectively. The input is 800kW at normal voltage and the induced line electromagnetic force is 2500V. Calculate the line current and power factor.

With a neat diagrams, explain the working of any two types of single phase induction motors and give their applications.

Briefly discuss the working of universal motor with the help of neat diagram.

Explain double revolving field theory for starting of single phase motors.

Explain the construction and working of a shaded pole induction motor.